####018007797#### FXUS61 KPHI 040830 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 430 AM EDT Sat May 4 2024 .SYNOPSIS... High pressure over New England will maintain an onshore flow through the next few days. A series of cold fronts approaches from the west through the weekend, with the second (and stronger of the two) front stalling out nearby by early next week. The stalled front lifts north as a warm front at some point in the Tuesday/Wednesday timeframe, bringing a return to above normal temperatures. && .NEAR TERM /THROUGH TONIGHT/... The base of high pressure centered over New England extends down into the Mid-Atlantic. An old warm front lies over the Appalachians, and a cold front is moving through the Great Lakes and into the Ohio Valley. High pressure slowly lifts to the north and east throughout the day today and into tonight. Several shortwaves will approach from the west, pushing those frontal boundaries towards the local forecast area. The first shortwave is moving through Maryland, and showers with isolated thunderstorms will move into the eastern shores of Maryland early this morning. Some brief downpours and a few rumbles of thunder can be expected. Those showers will taper off after sunrise as they run into the base of the high. Elsewhere, some marine stratus will move into portions of New Jersey and southern Delaware. That stratus will dissipate later this morning, but skies remain cloudy through the day as showers continue to develop well west of the region. Those showers will slowly track east, not making it into the far western portions of the forecast area until late in the afternoon and early evening. A cool day with highs in the 50s to low 60s, which will be some 10 to 15 degrees below normal for this time of year. Best chances for showers will be during the overnight period tonight, mainly for inland areas as those frontal boundaries wash out as they approach. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... A cold front approaches from the west on Sunday. With a slower approach, showers will mainly be north and west of the Philly metro through the morning, before pushing over the rest of the area through the afternoon and evening. The marine airmass in place will keep things stable, and really not expecting much in terms of thunder or heavy rainfall Sunday/Sunday night. Rainfall amounts will generally be around a quarter to three quarters of an inch of rain, spread out over a rather large period, so not expecting much in terms of hydro concerns. Temperatures will be in the upper 50s/low 60s, though some spots in the Delmarva will get into the upper 60s/low 70s. Temperatures won't drop much on Sunday Night, likely staying in the 50s. For Monday, temperatures moderate as a weak west/southwesterly flow takes over. The first of several shortwaves next week is expected to traverse the area, with some showers and thunderstorms potentially developing in the afternoon and evening. Some of the model soundings show decent instability with marginal shear, so can't rule out a strong to severe thunderstorm late Monday. However, not expecting the threat to be widespread at all. Will continue to monitor as we get in range of CAM guidance. Best chance to see any convection will be over Delmarva and southern New Jersey. Temperatures will be in the upper 70s/low 80s on Monday with mid to upper 50s/low 60s on Monday Night. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Unsettled conditions are expected for most of the week as a rather progressive pattern will be in place. Several shortwaves are expected to pass over the region. Lift will also be aided by a stalled boundary bisecting the area that will meander for the middle and end of next week. The front looks to venture northward on Tuesday into Wednesday, resulting in a period of above normal temperatures with upper 70s/low 80s expected. With a relatively warm and moist airmass in place, incoming shortwaves could potentially spark some showers and thunderstorms Tuesday/Wednesday PM. Wednesday afternoon/evening looks to be the most active in terms of convective weather, though too early to see if severe weather is on the table. The stalled boundary retreats southward towards the end of the week with onshore flow likely taking over, at least along the coastal plain. Depending on where this stalled boundary sets up will have implications on temperatures and thunderstorm potential on Thursday/Friday. Areas near and east of the front will be under the influence of the marine layer with cooler and more stable air, while areas west of the boundary are more unstable with warmer temperatures. A deepening trough will begin to move into the Mid- Atlantic, with a series of shortwaves/frontal systems moving through both Thursday/Friday. Both days will feature temperatures near/below normal, depending on where this lingering boundary sets up. Important to note that there remains a lot of uncertainty with the long-term forecast as models tend to struggle with a progressive pattern like this, and the placement of this boundary that will hang around through next week. As mentioned before, where that boundary sets up will have large implications on the forecast. We look to potentially shake this unsettled pattern once a sweeping cold front comes through late next week/early next weekend. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...MVFR and IFR CIGs at KMIV/KACY this morning, eventually lifting to VFR by this afternoon. MVFR CIGs at KTTN/KPHL/KPNE/KILG through daybreak will give way to VFR conditions. At KRDG/KABE, VFR. MVFR CIGs will spread from west to east starting at KRDG/KABE around midday, then MVFR CIGs will spread towards KACY prior to 00Z. SHRA arrive at KRDG/KABE prior to 00Z as well. E to SE winds 10 to 15 kt. Moderate confidence. Tonight...IFR conditions in stratus/BR/SHRA tonight. E winds 5 to 10 kt. Low confidence. Outlook... Sunday through Sunday Night...MVFR/IFR conditions expected with low ceilings. Reduced visibility likely with showers. Monday through Monday Night...Conditions gradually improve as the day goes on, likely back to VFR, though some showers/thunderstorms develop for the afternoon/evening, with restrictions possible if any storms move over the terminals. Tuesday through Tuesday Night...Primarily VFR though some restrictions possible with 20-40% chance of SHRA. Wednesday...Sub-VFR conditions possible (30-50%) with scattered showers/thunderstorms expected, especially in the afternoon/evening. && .MARINE... Sub-Small Craft Advisory conditions on tap today and tonight with E to SE winds 10 to 15 kt with gusts up to 20 kt and 3 to 4 ft seas. There is the potential for localized marine dense fog early this morning for areas south of Little Egg Inlet. Otherwise, mostly cloudy. Some showers may result in VSBY restrictions tonight. Outlook... Sunday through Wednesday...No long-fused marine headlines anticipated, though periods of showers/thunderstorms possible on the waters. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ SYNOPSIS...Hoeflich NEAR TERM...MPS SHORT TERM...Hoeflich LONG TERM...Hoeflich AVIATION...Hoeflich/MPS MARINE...Hoeflich/MPS ####018003466#### FXUS63 KDMX 040831 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 331 AM CDT Sat May 4 2024 .KEY MESSAGES... - Thunderstorms passing across Iowa early this morning into early afternoon with low end wind and hail risk. - Additional strong to severe storms on Monday evening into Tuesday && .DISCUSSION... Issued at 331 AM CDT Sat May 4 2024 A surface low has ejected across the central plains and towards the midwest through the overnight. Convection has ridden the surface warm front into the area with storms persisting thanks to low-level jet reinforcement. By 3 AM storms were entering western parts of the area, but have lost some steam thanks to weak instability into Iowa as the primary axis falls short of the area. This line of storms will continue progress across the area through the morning, exiting east in the early afternoon. MLCAPE through today remains around 500 J/kg with rather modest lapse rates, though deep layer (0-6 and 1-6 km) shear within sounding comes in at 40-50 kts. Given the parameter space, expect some small hail and wind risk with storms, however the severe threat remains on the lowers side into the afternoon. At the same time, hydro concerns remain in the back of our minds. Given recent heavy rains in recent days, a few areas are more sensitive (rivers in northern Iowa in minor flood and south-central Iowa which saw flash flooding earlier in the week). The good news here is that storms are fairly progressive which will mitigate most issues. HREF LPMM places a widespread 0.75-1.0" across the area with a few pockets of 1.5+" possible. Sunday will bring a welcome reprieve in the active period with weak ridging into the area behind the departing low. This is short-lived as the next system will be on our doorstep, swinging across the Rockies. By Monday will will move across the plains. In Iowa this will make for a breezy afternoon as the pressure gradient tightens ahead of the system. Recent model runs have slowed the progression of the system, lifting it across Iowa later Monday evening and into the overnight before exiting on Tuesday. A plume of instability cuts across the area with 1500+ J/kg MLCAPE and deep layer shear exceeding 40 kts. Model soundings indicate tall skinny CAPE profile with sweeping hodographs through the lowest 2 km. With 0-1 km SRH exceeding 200 m2/s2, tornadic activity is something to be aware of, in addition to the hail and wind concerns. The week remains active with another system on Wednesday/Thursday. Details on this will be forthcoming as this system is closely associated with the Monday/Tuesday system and will be heavily influenced by it. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1205 AM CDT Sat May 4 2024 MVFR to IFR cigs to move in with rain and thunderstorms. Have added thunder mentions to to all terminals as confidence is increasing in thunderstorms for even KMCW and KALO. Highest confidence at KFOD, KDSM and KOTM with vsby reductions and gusty winds also possible for KFOD and KDSM in the next 6 hours. Will continue to evaluate trends. Gusty northwest winds to follow departing rain, easing at sunset. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Hagenhoff AVIATION...Jimenez ####018005137#### FXUS63 KFSD 040832 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 332 AM CDT Sat May 4 2024 .KEY MESSAGES... - Rain will exit the CWA by mid morning, with total rainfall amounts of up to 0.50-0.75" over northwestern IA, and lesser amounts back to the north and west. Dry weather expected for the remainder of the day. - Cooler temperatures today (low 60s), with middle and upper 60s on Sunday. Dry conditions also expected on Sunday. - Winds approaching advisory criteria may arrive Monday, prior to the arrival of late afternoon and overnight thunderstorms. - The greatest severe weather risks continue to remain focused south of the Missouri River and Highway 20 corridor, however continue monitoring of the forecast is recommended. && .DISCUSSION... Issued at 330 AM CDT Sat May 4 2024 A frontal boundary/inverted surface trough resides east of Interstate 29 very early this morning. Current radar and observations indicate showers - with a few isolated lightning strikes - pushing eastward across the CWA. This in conjunction with midlevel frontogenesis and theta e advection pushing through the region. This area of showers will continue to push eastward through the morning hours, exiting the CWA sometime around 14Z. Additional rainfall amounts during the late night/early morning hours will range from a few hundredths in the western CWA, to a half to three quarters of an inch over northwestern IA. For the remainder of the day, surface high pressure begins to build into the region, with skies clearing from west to east through the day. With cold air advection on the backside of the system, afternoon temperatures will remain in the upper 50s to lower 60s. With the surface ridge axis sliding over the area tonight, light winds and clear skies will allow temperatures to fall into the upper 30s to lower 40s. The high pressure slides into the Mississippi Valley on Sunday. With that, winds will become southerly, increasing to 15 to 25 mph west of Interstate 29 in the afternoon as the surface pressure gradient tightens up - this the result of a deepening surface trough over eastern MT and WY. With weak warm air advection during the day, temperatures will bump up just a bit - into the mid and upper 60s. A well advertised upper level low over the Rockies lifts into the Northern Plains on Monday, as a surface low deepens over the western Dakotas on Monday into Monday night - pulling a warm front northward across the region during the day. Models still vary in the amount of instability over our area - generally ranging around 500-1000 J/KG in our southern CWA on Monday afternoon - depending on model of choice. Latest ensembles indicate only a 30-40% probability of CAPE greater than 1000 J/KG through the lower MO River Valley into northwest IA on Monday afternoon, while CIPS analogs and machine learning probs do give us at least some potential for severe storms on that day. So in summary, uncertainty still does exist, though cannot rule out a few strong to severe storms on Monday afternoon and evening - as supported by the SPC Day 3 outlook. Even so, the much better chance looks to be to the south of our CWA. In addition to the storm potential on Monday, it will also be quite windy - and there will be at least some potential for a Wind Advisory at some point. Any storms that develop will move eastward on Monday night, exiting the area sometime on Tuesday morning. We could receive another round of moderate to heavy rain with the system, and ensembles indicate around a 70% probability of portions of our area receiving a half an inch or greater of rainfall during this time frame. The upper level low meanders over the Northern Plains through at least midweek, before shifting to the east by the end of the week. This will keep at least small chances (20-30%) of showers for much of the week as various shortwaves rotate around the upper level trough. Highs through the period will mostly be in the 60s to lower 70s. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1029 PM CDT Fri May 3 2024 Frontal band of rain continues to make slow progress eastward late this evening. Meanwhile, convection over central Nebraska will continue to move east and northeast into the overnight hours. These two areas will merge after 1am over the Tri-State area, with potential for MVFR ceilings and visibility through the pre-dawn hours. In Sioux City,will not rule out some stronger 35 knot winds at times as convection passes through the area. Rain moves east of the CWA by 12Z, with MVFR ceilings hanging on through the morning. Eventually ceilings will scattered with some limited low-lvl instability shower/sprinkle potential in the afternoon. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JM AVIATION...Dux ####018006669#### FXUS63 KARX 040834 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 334 AM CDT Sat May 4 2024 .KEY MESSAGES... - Another round of rain moves through this morning and early afternoon, some thunderstorms possible south of I-90. Fog possible tonight along and east of the Mississippi River. - Dry and pleasant weather for Sunday and Monday with highs climbing back into the upper 60s to mid 70s. - An active stretch of weather from Monday night through at least Thursday as multiple rounds of showers move through. Severe weather risk for Tuesday is trending south. && .DISCUSSION... Issued at 330 AM CDT Sat May 4 2024 Today into Tonight: Cooler, Showers Especially this Morning Early this morning, a surface cold front stretched from Omaha, NE to Ashland, WI and steadily marches southeastward today ahead of a parent northern stream upper tropospheric trough quite evident in water vapor imagery over the Dakotas. An MCV developed across eastern Nebraska overnight as convection from the previous day congealed into a larger MCS that stretches down to central Oklahoma. This complex lifts along the frontal boundary this morning, and while expected to gradually weaken through the morning, should bring widespread precipitation with its passage. Indeed, every EPS/GEFS member has measurable precipitation and every CAM shows the system holding together with its passage, with minor timing differences driving down the PoP values in the blended CONSShort data. Therefore, leaned more aggressive with PoP coverage this morning with the notion that everyone should see rain at some point this morning. The MCV drags up a narrow moist sector of 55-60 F dewpoints today (currently south of Iowa), but confidence is not terribly high with how far north this airmass advances. Additional convection is progged to develop along the outflow-reinforced front in eastern Iowa this afternoon, which could easily cut off the moisture transport and leave us with little additional afternoon storm activity. The timing of this morning's storms will drive what transpires in the afternoon, but any threat for storms would exist over southwest WI before exiting before sunset. The combination of the morning rain and low clouds lingering for the afternoon will keep highs confined in the 50s to low 60s on the cool side of the boundary. Looking ahead to tonight, low clouds in the wake of this system clear out from west to east from 00-06Z with surface high pressure building in its wake. The setup is somewhat similar to what we saw yesterday morning with the widespread fog, but rainfall amounts today should be less and the clouds clearing sooner. This may limit the fog threat to east of the Mississippi River, and indeed the 00Z HREF has (noisy) 20-40% progs for visibilities under a mile in this region. Did include the mention of fog with this forecast update to account for this signal. Lows in favored sandy soil regions bottom out in the low to mid 30s tonight as well, which may necessitate targeted frost headlines. Sunday and Monday: Dry, Warming back Up Upper level ridging builds in during the day on Sunday and lasts well into Monday, keeping the area devoid of any precipitation. Did increase cloud cover for Sunday over the raw NBM guidance with the 03Z RAP and 06Z HRRR both showing convective temperatures being reached areawide by midday given the cooler airmass aloft and steep boundary layer lapse rates. This should facilitate the development of a cumulus cloud deck for the afternoon, though with general subsidence through the column and a stout 40-50C dewpoint depression dry wedge above the boundary layer, any clouds will be quite flat in nature. These types of sky coverage scenarios are very difficult for the blended guidance to depict and thus increased sky coverage just enough to get some mention of clouds in the worded forecast. Temperatures climb back into the upper 60s for highs today, with increasing southeasterly flow for Monday pushing highs up into the low to mid 70s. Latest trends in the medium range guidance have been to shift the threat for precipitation back into Monday night, so did remove the last vestiges of the 15-20% multi-run NBM blended PoPs from the southwestern forecast area for Monday afternoon. Monday Night through Friday: A Wetter Stretch of Weather Convection over the Central Plains Monday afternoon grows upscale into the evening as it moves into Iowa, gradually eroding the already narrow warm sector that stretches north of I-80. Overall trends in the medium range QPF data show a weakening system upon its arrival in our forecast area, likely after midnight for most locales. The overall severe weather threat for Tuesday hinges on the properties of the upper level wave pattern and whether or not recovery of the warm sector can take place in the wake of the morning MCS. The most probable scenario is that the early morning storms shunt the warm sector south as the upper wave pivots through, keeping any severe threat to the south. The upper tropospheric longwave trough separates from the flow and morphs into a cutoff low for Tuesday into Thursday, lingering over the northern High Plains during this time. This results in multiple, ill-timed waves of precipitation affecting the region. Temperatures cool down into the 50s to low 60s by the end of the week under this pattern, with the global guidance spread increasing in how long this cutoff low lingers beyond Thursday into next weekend. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1113 PM CDT Fri May 3 2024 VFR conditions look to continue through the overnight. Showers and perhaps a few thunderstorms will begin to move into the area towards the morning hours. Have maintained the previous forecasts trend with ceilings as guidance continues to indicate a period of MVFR. A few models suggest ceilings could lower to IFR for a time, especially at KRST, but confidence remains a bit lower so have opted to hold with MVFR and monitor trends/observations. Some reductions in visibility may be possible at times with heavier rainfall as well. Otherwise, light winds will begin to shift more northwest through the day. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Skow AVIATION...EMS