####018006708#### FXUS65 KGJT 252152 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 352 PM MDT Thu Apr 25 2024 .KEY MESSAGES... - Scattered showers and thunderstorms continue this afternoon and evening, with gusty winds and small hail the main threats. - Cool and unsettled weather continues Friday through the weekend as another system moves through. Accumulating mountain snowfall is likely, mainly above 9000 feet. - Warmer weather returns again next week. && .SHORT TERM /THROUGH FRIDAY NIGHT/... Issued at 352 PM MDT Thu Apr 25 2024 Scattered showers and thunderstorms have developed as expected this afternoon, in response to a strong mid-level disturbance rotating through overhead. The environment in place has been quite favorable for convection, characterized by strong diabatic heating, around 500 j/kg of SBCAPE... and steep mid-level lapse rates between 8.5 and 9.5C/km. Combined with forcing for ascent along a weak cold front, terrain enhancement, and modest height falls aloft, it's no surprise why current radar and satellite imagery appear the way they do. Overall, the main threat from showers and storms this afternoon and evening is gusty outflow winds with gusts upwards of 45 to 55 mph. Forecast soundings, along with this morning's 12Z GJT observed sounding, show a lot of dry air in the boundary layer... and while some of the stronger storms will be capable of producing small hail and brief heavier rain, the stout inverted V signatures suggest a lot of precip evaporating before reaching the ground. The added momentum of cooling/evaporating air aloft rushing to the surface will thus lead to an isolated wind threat through the evening hours. In fact, we've already observed this earlier today when strong outflow produced a 54 mph wind gust at Cortez-Montezuma County Airport. Otherwise, this afternoon's weather is a far cry from what we've had here as of late, with plenty of clouds and much cooler temperatures taking the edge off our early summer preview. Most storms should diminish within a couple hours after sunset with the loss of daytime heating and a stabilizing boundary layer. That being said, do expect some shower activity to linger into the overnight hours. By Friday morning, the disturbance that is currently passing overhead will be well to our east with a shortwave ridge building in from the west. This should result in a very brief period of mainly dry weather before the next storm system arrives later Friday afternoon. This next system is looking stronger than the first and will be accompanied by a much more potent cold front. Similar to today, we'll have another round of scattered to widespread showers and thunderstorms develop mainly after 21Z with gusty winds and small hail again the primary risks. In the wake of the passing cold front Friday night, attention then turns to winter as accumulating mountain snow is looking likely to round out the work week and start the weekend. While snow showers are probable in the mountains prior, the real action gets going Friday night into Saturday as strong forcing for ascent increases and becomes maximized within difluent flow and the left exit region of a strong upper level jet. The air aloft really isn't all that cold with 700mb temps generally 0C to -5C... but it will still be cold enough to support snow in the eastern Uintas and the Continental Divide mountains near and above 9000 feet. Given the late season nature of this storm and possible impacts at pass levels, decided to go ahead and issue a Winter Weather Advisory with this package for amounts of 6 to 12 inches from Friday night through early Sunday morning. For more details on how the storm plays out through then, see the long term discussion below. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Issued at 352 PM MDT Thu Apr 25 2024 On Saturday the low pressure tracks right over the forecast area, so plenty of lift and moisture in place for precipitation. Widespread showers are expected through out the day. This is supported by the high res models, which are now starting to cover that timeframe. Despite being a cold core system temperatures will be rather seasonal therefore snow levels are expected to be in that 7-9 kft range. Impacts from snow above these elevations will be limited by strong solar insolation. A few thunderstorms are possible, but the amount of instability will rely heavily on clouds clearing out. With the low center overhead wind direction will be very location and time dependent. Generally flow will go from southwesterly to westerly, but there may be a period of north/northeast winds so shower movement may be a bit chaotic compared to normal. On Saturday night the low exits out over the Plains. We should see a down tick with precipitation across our area. Although snow showers may linger in the mountains and produce messy travel around the passes. The QPF forecast has come down quite a bit in the last few model runs so confidence in the amounts is low. Just know that slick spots are possible Sunday morning generally at pass level. Moisture is slow to work out of here so with the steep lapse rates in place additional shower development is possible. Monday is looking mostly dry, but a system moving over the Northern Rockies could bring chances back to the northern CWA. Regardless zonal flow becomes established and temperatures begin to warm and by mid week southwest flow returns. This means daytime highs will be 10-15 degrees above normal. For the most part the entire week looks dry, but things could change. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1110 AM MDT Thu Apr 25 2024 An approaching cold front will bring some showers and a few thunderstorms to the region this afternoon with high elevation mountain snows possible overnight. Flight conditions should remain VFR though ILS breakpoints may be met for KASE, KEGE and KTEX in the evening hours after 00Z. Decided to include -SHRA for some of the TAF sites this afternoon. Brief MVFR can not be ruled out under the stronger cells. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Weather Advisory from 6 PM Friday to 6 AM MDT Sunday for COZ004-009-010-012-013-018-019. UT...Winter Weather Advisory from 6 AM Friday to 6 AM MDT Sunday for UTZ023. && $$ SHORT TERM...MDM LONG TERM...KJS AVIATION...TGJT ####018008694#### FXUS61 KOKX 252152 AFDOKX Area Forecast Discussion National Weather Service New York NY 552 PM EDT Thu Apr 25 2024 .SYNOPSIS... Strong high pressure building in through tonight will remain over the region into Saturday. A warm front lifts north of the area Saturday night into Sunday morning followed by high pressure through Monday. A cold front approaches Tuesday and moves across the region Tuesday night. Another cold front may pass through late Wednesday or next Thursday. && .NEAR TERM /UNTIL 7 AM FRIDAY MORNING/... Forecast on track early this evening. Northern stream trough remains over northern New England/SE CT tonight, with Canadian high pressure building in from the northwest through tonight. Ideal radiational cooling conds tonight with fresh Canadian airmass, clear skies, and light winds. Lows in the upper 20s to around freezing for interior of NE NJ, LoHud, and S CT, and pine barrens of LI where freeze warnings have been posted. Frost conditions for all but NYC/NJ metro and immediate surroundings tonight with lows in the mid 30s. Lows around 40 for NYC/NJ metro. && .SHORT TERM /7 AM FRIDAY MORNING THROUGH SATURDAY/... Northern stream shortwave trough gradually slides east on Friday, with upper ridging building in from the west Fri Night into Saturday. At the same time, good agreement in a vigorous closed upper low over the northern plains on Friday shearing into Ontario on Saturday. At the surface, the center of Canadian high pressure builds over the area Friday morning and sinks south of the region late Friday into Saturday. Unseasonably cool airmass remains over the region on Friday with light northerly flow giving way to aggressive afternoon sea breeze development once again. Despite plentiful sunshine and deep mixing, 850 temps just below freezing will only have temps topping in the upper 50s to around 60 (several degrees below seasonable). Another night of good radiational cooling conds Fri Night, although with a slightly moderated and moistened airmass, temps should be a few degrees warmer than tonight. Will likely have temps dropping into the lower to mid 30s with frost conditions across interior of NE NJ, LoHud, and S CT, and pine barrens of LI. Continued moderation of airmass on Saturday with strengthening return flow around high pressure to the SE and approaching warm front to the west. Strong sea breeze signature will likely push maritime airmass well inland and keeping temps several degrees below seasonable once again (upper 50s to around 60) for much of the coastal plain. In addition, increasing high clouds streaming in ahead of approaching warm front and over the top of the ridge axis will likely filter sunshine in the afternoon. Appears any light precip should stay west of the region during the day though. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Main story to start the long term will be anomalously strong ridging making its way over the eastern US Sunday into Monday before potentially breaking down Tuesday. A few shortwaves likely pass across the northeast Tuesday night into Thursday. The modeling is in good agreement through Monday on the larger scale pattern before timing/amplitude differences arise Tuesday through the middle of next week. *Key Points* *Mainly dry conditions expected with a few low chances of showers both Saturday night/early Sunday and then again Tuesday into Tuesday night. *A warming trend is likely to begin on Sunday and continue into Monday with temperatures potentially reaching 10-15 degrees above normal Monday, especially away from the immediate coast. *Temperatures remain above normal Tuesday through next Thursday. A warm front lifts over the area Saturday night and should end up north Sunday morning. Heights aloft are rising through this time frame and lift is weak. A few showers are possible with the front, especially across the interior Saturday night. The continuation of the building ridge over the eastern states on Sunday will likely result in at least partial clearing through the day. A SW flow develops behind the passage of the warm front allowing temperatures to warm significantly compared to recent days. There is a significant amount of spread in high temperatures for Sunday, especially for locations away from the immediate coast. For some of the warmer locations the NBM deterministic actually falls below the 25th to 75th percentile of the ensemble. There should be enough clearing along with building heights aloft and little onshore flow influence for temperatures to end up on the higher side. Have decided to blend in the NBM 50th percentile for now away from the coast which yields highs middle to upper 70s. The 75th percentile of the NBM indicates temperatures could reach or exceed 80 degrees. Onshore flow over Long Island and southern CT likely holds temperatures in the 60s with some locations potentially close to 70 degrees. The ridge axis will be overhead on Monday. Strong subsidence will likely lead to even warmer temperatures compared to Sunday. The NBM deterministic is near the 25th percentile with much of the spread on the warmer side of the warmer side of the ensemble. Have once again blended in the NBM 50th percentile for the NYC metro, NE NJ, and Lower Hudson Valley/interior SW CT. The flow is weak during the first half of the day, but sea breezes should develop in the afternoon. Forecast highs range from the lower to middle 80s in the warmer spots to the upper 60s to middle 70s near the coast. High temperatures spread only increases further on Tuesday. For example at KEWR, the 25th percentile is 71 and 75th percentile is 87 degrees. Given that this is next Tuesday, have gone close to the NBM deterministic for now (60s east and lower to middle 70s west). The warmer highs in the ensemble spread could easily be realized away from the coast if the front is slower and ridge does not break down as quickly. The aforementioned cold front swings through sometime late Tuesday or Tuesday night. A few showers and potentially a thunderstorm could accompany the frontal passage. The CSU MLP has been indicating a very low probability for a severe thunderstorm with this front during its last few cycles. Confidence is very low with any convection at this time range. Confidence is also low in sensible weather details for Wednesday and Thursday and have followed the NBM deterministic. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... Strong high pressure will build in through the TAF period. VFR. SSE winds this afternoon at 10 kt or less will become light and variable overnight. Winds will then return out of the SE late Friday morning into Friday afternoon. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... No unscheduled AMD expected. OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY... Friday: VFR. Saturday and Sunday: Mainly VFR. Only slight chance of a shower Sat night into early Sunday morning. Monday: VFR. Tuesday: MVFR or lower possible in afternoon showers and possible thunderstorms. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90 && .MARINE... Winds and seas will remain below advisory levels through early next week. Coastal jet development Sat aft could have marginal SCA wind gusts (20-25kt) for ocean waters and nearshore around the entrance to NY Harbor. Warmer air moving over the colder ocean early next week could develop fog, but it is much too early for any specific details on timing and extent. && .HYDROLOGY... No hydrologic concerns through the middle of next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Freeze Warning from 2 AM to 8 AM EDT Friday for CTZ005>008-012. Frost Advisory from 2 AM to 8 AM EDT Friday for CTZ009>011. NY...Freeze Warning from 2 AM to 8 AM EDT Friday for NYZ067>070-079- 081. Frost Advisory from 2 AM to 8 AM EDT Friday for NYZ078-080. NJ...Freeze Warning from 2 AM to 8 AM EDT Friday for NJZ002. Frost Advisory from 2 AM to 8 AM EDT Friday for NJZ004-103-105- 107. MARINE...None. && $$ SYNOPSIS...DS/NV NEAR TERM...DS/NV SHORT TERM...NV LONG TERM...DS AVIATION...FEB MARINE...DS/NV HYDROLOGY...DS/NV ####018004437#### FXUS65 KFGZ 252153 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 253 PM MST Thu Apr 25 2024 .SYNOPSIS...Look for windy, cooler, and unsettled conditions through Saturday as a pair of weather disturbances move across Arizona. Scattered showers continue through this evening. Another round of rain and higher elevation snow arrives late Friday into Saturday. Fair and warmer weather returns on Sunday through much of next week. && .DISCUSSION...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...Thursday 25/18Z through Friday 26/18Z...Look for continued SHRA/TSRA through at least 00Z, causing periods of MVFR ceilings and visibilities. Strong wind gusts, up to 35 kts, expected throughout the afternoon. S-SW winds 5-15 kts forecast overnight, but localized areas along higher terrain could remain breezy. OUTLOOK...Friday 26/18Z through Sunday 28/18Z...MVFR/IFR conditions will increase west to east from SHRA/TSRA/SHSN beginning 18Z Friday. Showery weather will continue through at least 00Z Sunday. Then, widespread VFR conditions should return. Look for SW winds 15-25 kts 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. Wind Advisory until 8 PM MST /9 PM MDT/ this evening for AZZ013- 014. && $$ PUBLIC...JJ AVIATION...Konieczny FIRE WEATHER...Konieczny For Northern Arizona weather information visit weather.gov/flagstaff