####018011089#### FXUS63 KAPX 260345 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 1145 PM EDT Thu Apr 25 2024 .KEY MESSAGES... -- Elevated fire danger Friday afternoon. -- Increasing confidence in rounds of showers and thunderstorms impacting northern Michigan from Friday night through Monday. -- Chance for severe thunderstorms, particularly later Saturday into Saturday night across northern lower Michigan. && .SHORT TERM /THROUGH SATURDAY/... High pressure still focused just to our east over Ontario...with PV maxima dropping across the CWA attm. Light and variable winds with lake breeze development today...and seeing a very few cu pop up over NE Lower, where some upsloping may be aiding in lift and saturation, combined with some slight moisture advection off the lake as that weak bit of PV moves through. Expecting high pressure to remain over the area tonight...though return flow should rotate into the region going into Friday morning, and especially Friday afternoon, with increasing warmth aloft, as well as an increase in overall moisture. However...southeast flow hangs on into Friday as well, and antecedent dry air mass should preclude most, if not all, precip from reaching the ground over the region till beyond this period. Primary Forecast Concerns: Increasingly warm and breezy, remaining dry...Expecting temps aloft to increase through the day Friday, and with mixing up to around 850mb, think highs in the upper 50s to lower 60s are quite probable, especially considering we should remain largely clear...and temps will not fall as much tonight as they did last night. With better downsloping over NW Lower...think some upper 60s could be possible as well...though I do have to admit that we should start to get better mid/high cloud coverage into that area with time in the afternoon. Current dry air mass will take time to saturate...and suspect this may hold off even some of the cloud cover until later in the afternoon/evening; even less can be said for precip, which should hold off till Friday night and beyond. Some suggestion that another lobe of lower dewpoints could pivot over the region from north to south Friday, which could allow for afternoon RHs to fall even further below the usual 25 percent criteria for fire weather thresholds. Have not gone quite this aggressive, but have elected to keep dewpoints (and subsequently, RHs) a touch lower even so. Additional concerns for fire weather as pressure gradient begins to strengthen with system tracking across the Plains; expecting 5-10kts sustained winds, which could gust as high as 20-25kts by evening. Admittedly, this is more of a warm advection setup for winds, which typically would not be as favorable for gustiness...though do think the antecedent dry air mass and good potential for mixing could aid in better gusts this time around...at least, while the sun is out. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Pattern Synopsis / Forecast: Active baroclinic zone will really get its act together over the course of the weekend as a complex setup of shortwaves and associated surface low pressure centers / frontal boundaries pass through the upper Great Lakes region, dispatching the dry influences of surface high pressure progged to be moving off the Atlantic coast of New England. The action begins Friday night as a surface warm front moves into the region, bringing a round of showers and potentially some thunder too. The next car in the metaphorical atmospheric train will be surface low pressure advancing east from Wisconsin into the U.P., drawing in a warmer and potentially much more unstable airmass before a surface cold frontal boundary moves into the region and sparks off another chance for showers and storms late Saturday, some of which could be strong to severe. This frontal boundary largely becomes stationary over the region by Sunday, continuing unsettled weather potential Sunday into Monday as yet another low pressure center works into the Great Lakes. The passage of this low pressure center should mark the end of the active stretch of weather, with surface high pressure progged to intrude into the Great Lakes as we move closer to midweek. Primary Forecast Concerns: Friday Night Convection: Despite warm / moist advection moving into the region, there will be some barriers to overcome as we progress into the overnight hours. Stout low level dry layer will impede the initial advances of a stratiform rain plume well ahead of the surface warm frontal boundary. It wouldn't be overly surprising for this plume to pass through the region with more of a whimper considering progged soundings display dewpoint depressions as high as 30 Celsius across the southwest part of the CWA around 00z Saturday. The most appreciable rainfall from this frontal passage will come later in the overnight when steepening lapse rates aloft (up to 7 Celsius / km) and 850mb warm advection drive elevated instability associated with the warm front. In theory, would like to see steeper lapse rates to drive instability up for better thunder coverage, but the moistening airmass should provide better rainfall potential for places that see repeated shower passages Friday night regardless. While instability is low (generally 100-400 J/kg), suppose an embedded rumble of thunder or two cannot be ruled out. Overall, looks like most spots probably see a general 0.25" or less Friday night, though localized areas that see repeated downpours could observe 0.75"+. At this time, severe weather potential looks quite low Friday night into Saturday morning. Saturday - Saturday Night: Uncertainty begins to riddle the forecast as we progress into Saturday, particularly with respect to the position of the surface warm frontal boundary. Most guidance has the surface warm front clearing the Straits and stalling out somewhere between the Bridge and the Soo, but there is a modest amount of guidance that has the front stalling out around the M-32 area. The former solution would generate more clearing / destabilization potential amid warmer temperatures across northern lower into the day Saturday, possibly as high as the upper 70s for some, while the latter solution brings about a cloudier and cooler solution (upper 50s and lower 60s) with a stable layer in the low levels and thus suppresses the majority of surface based convection to the south and west. Considering favorable low pressure position based off severe climo for northern Michigan and the 500mb ridge axis located just to our east, this in theory should allow for an easier warm frontal passage, despite the suppressing efforts of the colder Great Lakes. In the event that this solution pans out, this opens a Pandora's Box of convective potential across the region. Being in the vicinity of the triple point of the system will lead to favorable dynamics aloft to contribute to severe weather potential later Saturday into Saturday night as the surface low and associated cold front move into the region. Bulk shear increases considerably with the intrusion of the triple point (as high as 40-50kts). In addition, SRH values balloon above 200 m^2/s^2, indicating ample potential for rotating updrafts to materialize with any surface based storm that initiates. The final thing that will need to come together will be the maintenance of surface / low level moisture. Guidance wants to keep dewpoints well into the 50s and even into the lower 60s, which would lower cloud bases and bypass the potential suppressing nature of warmer air aloft in the profile. If we can achieve the higher end of this dewpoint range, coupled with the other aforementioned favorable dynamics, this could lead to all hazards being on the table Saturday evening / early overnight, with heavy emphasis on wind and hail (non-zero chance for these hazards to be locally significant if a more discrete / supercellular storm mode can be realized). Tornadic activity will be somewhat questionable owing to shear vectors being more parallel to the cold front as opposed to normal to the boundary as it approaches northern Michigan (thus leading to the eventual stationary nature of the front), but risk still remains non-zero. Additionally, the parallel relationship of shear vectors and frontal orientation could set up a heavy rain sequence with any potential training thunderstorms as PWATs swell to 1.00-1.25 (200-300% of climo normal). This setup has a very low floor, but a high ceiling that can't be overlooked despite ongoing forecast uncertainty. This is reflected by SPC already electing to place northern lower Michigan within the Day 3 Slight Risk (level 2/5) for the conditional threat of severe weather. Numerous more updates are to be had in the coming forecast cycles as details on the evolution of this sequence become clearer. Rest of the Period: The cold front will stall out overhead and become stationary by Sunday, and with additional disturbances expected to ride this area of forcing, this spells additional rounds of showers and storms at times Sunday into Monday, bringing additional rainfall. Eventually, low pressure will pass through the region and the stalled front will be forced eastward by intruding high pressure. By Tuesday, conditions look to be drier but still on the mild side, with highs in the upper 50s to upper 60s and lows generally in the 40s. One final note- considering that we will be dealing with warm daytime temperatures and mild nights coupled with mild temperatures accompanying rainfall, this should spell the arrival of spring greenup in the next week or so, particularly across northern lower Michigan. This could open the door for any frost / freeze impacts beyond the forecast period to be amplified. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Large area of strong high pressure centered over the Great Lakes region will slowly push eastward into New England over the next 24 hours. Skies will remain clear overnight into Friday... but clouds will increase by Friday night as moisture begins to surge northward in advance of a developing storm system over the Central Plains. Solid VFR conditions are expected at all Eastern Upper and Northern Lower Michigan TAF sites thru Friday evening. Chances of showers will begin to increase from SW to NE across our area late Friday evening and overnight. Light SE winds overnight will strengthen to 15 to 25 kts on Friday. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ SHORT TERM...FEF LONG TERM...HAD AVIATION...MLR ####018007457#### FXUS63 KJKL 260345 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 1145 PM EDT Thu Apr 25 2024 .KEY MESSAGES... - Frost is possible in some valleys again tonight. - A warming trend begins on Friday, with well above normal temperatures then expected early next week. - There is a small potential for showers in association with a warm front Friday and/or Friday night. There is a better chance at showers and thunderstorms as we move into the new work week due to the approach of a dying cold front. && .UPDATE... Issued at 1145 PM EDT THU APR 25 2024 The clouds are fairly thick for the southern 2/3rds of the area helping keep temperatures up and this will likely prevent any frost concerns for most of the area. Have updated the forecast mainly to adjust the sky cover through the night and fine tune the frost threat in addition to adding in the latest obs and trends for the T/Td/Sky grids. These minor adjustments have been sent to the NDFD and web servers along with a freshening of the zones and SAFs. UPDATE Issued at 745 PM EDT THU APR 25 2024 23Z sfc analysis shows high pressure to the north of the area keeping skies mostly clear for the northeast half of the JKL CWA. However, more, mainly high, clouds are affecting the southwest portion of the area. Expect some ridge to valley differences in temperatures to show up through the night with areas of frost possible in the deeper northeast valleys. Currently, temperatures across eastern Kentucky vary from around 60 degrees north to the mid and upper 60s in the southeast. Meanwhile, amid light northwest to north winds, dewpoints range from the low 40s southwest to around 30 degrees in the northeast. Have updated the forecast mainly to fine tune the limited river valley fog in the northeast late tonight and to include the latest obs and trends for the T/Td/Sky grids. These minor adjustments have been sent to the NDFD and web servers. && .SHORT TERM...(This evening through Friday night) Issued at 325 PM EDT THU APR 25 2024 Surface high pressure centered over far southeastern Ontario late today will move east over New England tonight, providing us with continued fair weather in a cool and dry air mass. Aloft, ridging will arrive from west tonight, getting squeezed between a slowly departing trough to the east and a storm system impinging on the ridge from the west. High clouds associated with warm air advection may begin to spill through the ridge tonight, but will probably be insufficient to have much impact on temperatures. Considering the dryness of the air mass, it would appear that our northern valleys will again be marginally cold enough for some frost by morning. The aforementioned storm system will slowly move from the central plains to the upper Midwest on Friday and Friday night as surface high pressure and ridging aloft shift slowly away to our east. This will result in increasing warm air advection for the local area ahead of a warm front. This front currently lies from the central plains to the FL panhandle. It will approach us on Friday and arrive Friday night, but will become ill-defined as it arrives, with the greatest push of warmer air being to our north and northwest. Models have not been consistent on the prospects of precip for our area with this front, and have been focusing the greatest POP to our northwest and north in the stronger warm air advection. In the uncertainty, will continue to carry low POPs in the forecast Friday and Friday night, along with an increase in clouds. Despite the clouds and possible precip, warm air advection should result in higher temps on Friday, with clouds then also helping to hold readings higher on Friday night. .LONG TERM...(Saturday through Thursday) Issued at 340 PM EDT THU APR 25 2024 A busy upper air pattern will be in place across the CONUS to begin the extended portion of the forecast. A large and developing trough of low pressure aloft will be taking shape over the mid Rocky Mountain region and will be pushing slowly eastward over the weekend. Another smaller but robust area of low pressure will be bringing showers and storms to the middle of the country as it moves northeastward into southeastern Canada the first half of the weekend. As this system moves of to our north, a ridge of high pressure will spread across the region over the upcoming weekend, and will bring very warm and dry weather to eastern Kentucky during that time. Although there are some timing differences amongst the various models, the general agreement is for high pressure to dominate our weather this weekend and to bring much warmer than normal temperatures to the area. After a couple of days of dry weather, a strong area of low pressure is forecast to intensify as it moves through the Great Plains to end the weekend and into the first of the new work. A vigorous upper level system will steer and help strengthen the surface low as it moves our way. However, with a strong ridge of high pressure still parked over the southeastern CONUS, the trough to our west will still have a difficult time moving our way, as the stubborn high will be slow to break down. The ridge should finally break down and move far enough east to allow a weakening cold front to push through the Ohio and Tennessee Valleys Monday through Tuesday. This system will bring widespread showers and scattered thunderstorms to our area, especially from around dawn Tuesday through early Tuesday evening, as the surface boundary moves through. The models are showing enough instability for thunderstorms to form, but with the front shearing out as its parent low moves quickly northeast into Canada, there is still quite a bit of uncertainty regarding storm strength, as we'll continuing going with garden variety thunderstorms for our area for now. Any storm might produce frequent lightning and brief heavy downpours. Temperatures will average well above normal through the extended, with ranging from the upper 70s to mid 80s each day. Nightly lows will also be quite mild, and will range from the mid 50s to lower 60s. We will see a few nights with marginal conditions for ridge valley temperature differences, and should see at least a hint of this Saturday night and Sunday night, and again Tuesday night and Wednesday night, as high pressure will be influencing our weather during this time. Winds will increase a bit and become gusty early next week, as strong low pressure moves by to our northwest and north. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 805 PM EDT THU APR 25 2024 Generally VFR conditions and winds less than 10 kts - switching south on Friday - are forecast through the period. Very localized valley fog may occur in southeast Kentucky overnight and early Friday morning, but are not expected to affect any TAF sites. Additionally, shower chances through the day Friday will be too low to include as even VCSH in the TAFs at this point. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...HAL LONG TERM...AR AVIATION...HAL/GREIF ####018004846#### FXUS65 KFGZ 260345 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 845 PM MST Thu Apr 25 2024 .SYNOPSIS...A lull in precipitation will take place tonight and Friday morning before more windy, cooler, and unsettled conditions return as the second weather disturbance moves across Arizona. Another round of rain and higher elevation snow arrives late Friday through Saturday. Fair and warmer weather returns on Sunday through much of next week. && .UPDATE...Winds and showers diminished this evening as a short wave of low pressure moved into New Mexico. Have updated forecast to end the wind advisory earlier this evening. Also removed showers as the atmosphere stabilized. && .PREV DISCUSSION /453 PM MST/...The first of a pair of low pressure systems is moving through northeastern Arizona this afternoon. A large area of rain and thunderstorms (with snow down to 6500 ft!) moved from Yavapai Co up to I-40 in the Flagstaff region this morning. That has mostly dissipated, but has been replaced by convection this afternoon as daytime heating has combined with cold mid-level temperatures to increase instability. Wind shear is weak, but CAPE values support some locally heavy downpours with hail from pea size up to 1/2 inch. This activity will wind down early this evening. Friday through Saturday - the second low pressure system will move into northwest Arizona late Friday afternoon and then to near 4 corners by mid day Saturday. Out ahead of the low, wind gusts of 35-45 mph are likely, with the strongest winds along the north side of the Mogollon Rim/White Mtns toward the northeast. A Wind Advisory has been issued from 9 AM to 7 PM MST for these areas. By later in the afternoon, showers and a few thunderstorms are forecast enter northwest Coconino County, gradually moving southeast through the evening and overnight hours. This second system is quite a bit colder than today's, and we expect snow levels to fall to 6500-7000 feet by later in the evening through Saturday morning. The forecast QPF values have also increased with our latest forecast package, with high country locations in the 0.20-0.50" range and less than 0.20" for the valleys. Snow amounts are tricky due to the relatively warm ground and time of year, but during the overnight/early morning hours there could be some minor impacts to travel above 6500-7000 feet. Forecast snow amounts are still generally 1" or less, higher over the peaks. This will move out by Saturday evening, with precip chances ending. Sunday through Wednesday - dry zonal flow over our area as the storm track shifts north. Temperatures Sunday warm to near normal for this time of year, then continue warming to around 10 degrees above normal by Wednesday. Look for typical springtime winds, but nothing out of the ordinary - in the 10-20 mph range. && .AVIATION...Friday 26/00Z through Saturday 27/00Z...SH/TS activity is diminishing this evening, but some isolated activity is still going and will persist for the next 1-3 hours. Current band of storms will be impacting KFLG shortly. Confidence is low that the band will hold together and reach KSEZ. Dry weather tonight with S-SW winds 5-15 kts forecast: localized areas along higher terrain could remain breezy. Winds pick up again out of the SW tomorrow afternoon, gusting 20-30 kts for many locations. OUTLOOK...Saturday 27/00Z through Monday 29/00Z...MVFR/IFR conditions will increase west to east from SHRA/TSRA/SHSN beginning as early as 18Z Friday. Showery weather will continue through at least 00Z Sunday. After, widespread VFR conditions return. Look for SW winds 15-25 kts late on Friday, becoming W 15-25 kts on Saturday. Winds gusts could reach 30-40 kts during each afternoon of the outlook period. && .FIRE WEATHER...Friday and Saturday...Look for continuous rainfall/thunderstorms, with high elevation snow, starting Friday evening. Active weather will persist through Saturday. Expect SE winds 15-25 mph, gusting up to 40 mph on Friday, becoming slightly lighter W winds on Saturday. Sunday through Tuesday...Temperatures will quickly warm each afternoon, reaching 5-10 degrees above normal by Tuesday. Minimum RH values will drop down to single digits-20s each afternoon. W winds 5- 15 mph forecast for Sunday and Monday, becoming more southerly on Tuesday. && .FGZ WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 9 AM MST /10 AM MDT/ to 7 PM MST /8 PM MDT/ Friday for AZZ009-012>017-039-040. && $$ PUBLIC...MAS/JJ AVIATION...RKR FIRE WEATHER...Konieczny For Northern Arizona weather information visit weather.gov/flagstaff ####018008489#### FXUS63 KBIS 260350 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 1050 PM CDT Thu Apr 25 2024 .KEY MESSAGES... - Showers are likely (60-90%) tonight through Friday, with the highest probabilities across central and eastern North Dakota. - Isolated thunderstorms may be found tonight through Friday. Severe weather is not expected at this time. - Cooler temperatures on Saturday and Sunday, with low to medium chances of rain showers across southern and central North Dakota. - Temperatures warm up back to above normal next work week, with low chances for showers most days. && .UPDATE... Issued at 1050 PM CDT Thu Apr 25 2024 Minor updates late this evening mainly for current radar trends. Showers look to linger across much of central North Dakota tonight, spreading slowly eastward. Thunderstorms have diminished in coverage, and overall are now expected to be isolated in coverage through the night. Limited thunder mention to slight chance as a result. More widespread showers are then expected for much of Friday, with perhaps some isolated thunderstorms across southern and eastern portions. Gusty winds in the east have come down some. They may remain elevated through the night although below advisory criteria. Gusty northeast winds could then be found across the west tomorrow. UPDATE Issued at 705 PM CDT Thu Apr 25 2024 Limited updates needed so far this evening. In the east near to isolated advisory winds are being reported. Coverage was more isolated to scattered thus held off on an advisory at this time. These winds could gust 45 to 50 MPH this evening, diminishing around sunset. Meanwhile in the west and south central, continue to monitor thunderstorm development. Pockets of MUCAPE near 1000 J/KG remain, although shear values of 20 to 25 knots are proving to be not enough to sustain severe thunderstorms in ND at this time. That being said, still cannot rule out an isolated strong storm through the evening. Hail and perhaps gusty winds would be the main threat, although still expecting storms to be sub severe. Brief heavy rain could also be possible as precipitable water values are currently above normal for this time of year. Overall will continue to monitor winds and thunderstorms with little updates needed at this time. && .DISCUSSION... Issued at 304 PM CDT Thu Apr 25 2024 Currently, mostly mid to high level clouds are present across the area, with widespread temperatures in the low to mid 70s. There is still the potential for some areas out west to reach 80 within the next few hours, however the intrusion of thicker clouds from Montana and western South Dakota may limit those chances. Some cumulus has begun to form across the border in eastern Montana as well. Winds across the area are out of the south southwest, with some places in the James River Valley reaching sustained wind speeds in the 20 to 30 mph range, with occasional gusts nearing 35 mph. These winds are expected to decrease near sunset, when mixing weakens. We are still on track to receive our first real chance at some convection and the development of thunderstorms. Recent deterministic guidance indicates a corridor of 1000 - 2000 J/kg of MUCAPE, along with modest lapse rates, supporting the potential for the development of thunderstorms. However, shear continues to be the main limiting factor, with 0-6 km shear maxing out at 15 to 20 kts across the region with highest instability. Should any storms develop, small hail and gusty winds will likely be the main concerns, as these storms will not be able to sustain themselves without the shear. Gusty winds from these storms may continue as the storm collapses as well. Initially, these storms will begin to develop across the southwest during the late afternoon and early evening hours, before spreading across the rest of the area after sunset. CSU machine learning continues to advertise a low chance for severe hail during this period, mostly across western portions of the state. Our area is still only in a general thunder risk from the SPC, but the Marginal Risk (level 1 of 5) has been expanded up to our southern border. Following this round of thunderstorms, a warm season Colorado Low is forecast to move to the south of the area through Friday, bringing much of the area a period of showers. Wrap around moisture long the northern periphery of the surface low will make its way into the southern half of the state late tonight, expanding northward through the day Friday. Chances for precipitation at its peak will range from 20 to 30% across the far northwest, to 80 to 95% for nearly the entirety of central North Dakota and the James River Valley. Precipitable water values are forecast to be near 1.00", which approaches the 90th percentile of the precipitable water climatology. Parts of south central and the southern James River Valley currently have a 45 to 75% chance of exceeding 0.50" of rain, while the chances for exceeding 1.00" remain rather low, at around 10 to 20% for the same area. Most of the area is expected to see at least some rain through the day Friday, with chances tapering off overnight and into Saturday as the surface low pushes out into the Great Lakes region. A cold front is forecast to drop down across the area from the north this weekend, with high temperatures on Saturday and Sunday forecast to be a bit cooler than what we have been seeing lately. Widespread highs are forecast to be in the upper 40s to the upper 50s, with overnight lows in the 30s to lower 40s. While some areas may see temperatures below freezing, precipitation is unlikely to occur in those areas, so any concerns for snowfall are minimal. As that cold front moves through, a secondary, weaker low pressure system is forecast to take a similar path to the previous Colorado low, just displaced a bit further south. Moisture associated with this system are expected to be reduced, with chances for precipitation mostly displaced further southeast. Chances for exceeding 0.50" will be rather low, only maxing out around 20 to 30% in the far southern James River Valley, with most locations remaining lower than 10%. After these systems move through, upper level flow is expected to be a bit more zonal, with an upper level ridge moving into the area from the west. Temperatures are forecast to increase Monday and through the rest of the week, increasing into the 60s to lower 70s. However, there is still some disagreement in the placement and strength of this ridge, which would affect how active the pattern becomes. Current WPC cluster analysis suggests two separate scenarios: 60% of members suggest a stronger ridge, leading to a warmer, less active, and therefore drier pattern, with only occasional daily chances for afternoon and evening showers. The other 40% of members suggest a more southward displaced ridge, leading to a more active and wet pattern, with the potential for greater chances for showers and thunderstorms. Either way, next work week is looking to be a bit warmer than the weekend that precedes it. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 705 PM CDT Thu Apr 25 2024 Periods of showers and thunderstorms will bring MVFR to IFR conditions at times through the forecast period. This evening, showers and thunderstorms will push into western North Dakota. These could bring periods of MVFR conditions. Meanwhile breezy winds and increasing clouds could be found across the central and east. Tonight, showers and thunderstorms transition to more widespread showers that then look to linger across much of the forecast area through Friday. Prevailing showers are in most TAF sites as a result, with the exceptions being in northwestern North Dakota including KXWA. These widespread showers could bring MVFR to IFR ceilings. Breezy southeast winds could linger across the east tonight into Friday. Meanwhile a breezy northeast wind could develop across the west on Friday. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Anglin DISCUSSION...Besson AVIATION...Anglin