####018007942#### FXUS63 KABR 040215 AAB AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 915 PM CDT Fri May 3 2024 .KEY MESSAGES... - A banded rainfall event over the southern/eastern portions of the forecast area will relocate to mainly just the eastern portion of the CWA through late tonight. Rainfall amounts in excess of one half inch can be expected overnight. - High pressure will bring dry and warmer conditions this weekend. - A much larger system looks to affect the region on Monday, with widespread moderate rainfall. The threat for severe weather still appears low at this time (higher across NE/KS/OK), but we will continue to monitor trends. && .UPDATE... Issued at 845 PM CDT Fri May 3 2024 A very favorable set-up for banded precipitation has unfolded (and is ongoing), between strong low to mid-level fronto-forcing and a 100+knot upper level speed maximum. For a while, there were some strong returns showing up within this band of rain, and some of that could have been caused by bright-banding (occurs when the radar assigns too high a reflectivity/rainfall rate to water coated snowflakes falling through the melting layer). Legacy and dual-pol rainfall estimates off the KABR 88D have maxed out at ~2.00-2.50 inches and ~1.50-2.25 inches, respectively. MRMS estimates are lower (more reasonable) ranging from ~0.50-0.75 inches of rainfall along a stretch from northern Hand County through Spink and Clark Counties up into Day County. There's plenty more forcing/lift to be had over the next ~6 hours or so, particularly over northeast South Dakota into west central Minnesota. Perhaps another 0.10 to 0.25 inch of rain could happen along and east of a line from Miller, SD to Wheaton, MN. Low temperatures still look okay for tonight. UPDATE Issued at 647 PM CDT Fri May 3 2024 See below for an aviation forecast discussion for the 00Z TAFs. && .SHORT TERM /THIS EVENING THROUGH SATURDAY NIGHT/... Issued at 315 PM CDT Fri May 3 2024 An upper level trough currently west of the region will track across the Dakotas tonight, with a fairly potent shortwave affecting mainly the eastern part of the CWA. The trough weakens as it exits the area on Saturday, with ridging then building in Saturday night. At the surface, the region is currently situated between a low pressure system over southern Ontario and a low over Colorado. The boundary between these two systems will be the focus for rain late this afternoon and tonight as the aforementioned shortwave moves over the area. Currently seeing some scattered shower activity over mainly the western half of the CWA, but expect this area of rain to become more of a line from southwest to northeast by this evening, generally extending along and east of a line from west central Minnesota to Murdo. The area of rain will then spread eastward tonight. Right now, thunderstorm potential looks to stay south of the CWA, but cannot rule out a stray thunderstorm maybe affecting the southeastern CWA this evening. The highest rainfall amounts are expected along and east of a line from Wheaton, MN to Murdo, where one quarter to one half inch looks to occur. Should a thunderstorm develop, there could be some locally higher amounts. High pressure will settle over the region Saturday and Saturday night, bringing a return to dry conditions. Low temperatures tonight will range from the lower 30s along and west of the Missouri River, to the lower 40s across west central Minnesota. High temperatures on Saturday will be in the upper 50s to mid 60s. Lows Saturday night will be in the mid to upper 30s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 315 PM CDT Fri May 3 2024 This forecast period begins Sunday morning on a relatively quiet note compared what were anticipating to be another round of active and wet weather through the majority of next week. Upper level ridging will build overhead on Sunday in response to an upper level trough/low moving through the Great Basin and adjacent regions of the western CONUS. Sfc high pressure will be positioned off to our east while low pressure will be situated across the lee of the Rockies and Northern High Plains on Sunday. Southerly low level flow will intensify through the daytime as the pressure gradient tightens. Increasing southerly winds through the day will potentially reach advisory criteria, especially across our western zones. NBM probabilities of seeing max wind gusts greater than or equal to 34kts(40mph) is high(70-100%) along and west of the Missouri Valley. At this point in time, the thinking is that this is a bit on the high category or extreme, so will continue to take a more conservative approach and keep an eye on trends with incoming future guidance data. With a decent amount of sunshine to round out the weekend and dry conditions expected, we should see a nice warm up. 950mb temps are expected to reach about +13C to +19C which translate to highs in the 60s to low 70s across the forecast area. Unfortunately, all good things have to end sometime and we'll see the pattern shift quickly by Monday into a more active and wet one. The aforementioned upper low is progged by both deterministic and ensemble guidance to track northeastward out of the Rockies into portions of the Northern High Plains and Northern Plains early next week. This system looks to be rather vigorous on Monday as sfc low will track into the Central Plains and shift northward into our region. Severe weather parameters looks best across the Central Plains and south of our region by Monday afternoon and evening, however we can't totally rule out some stronger activity in parts of our area. As of right now, our forecast area is just outside of the northern fringe of the better instability. MUCAPE values on the order of about 300-500 j/kg is possible, especially across our southern zones with far more higher values to the south in parts of NE and KS. We'll just have to keep track of the trends over the next couple days to see if there's any movement farther north with these better ingredients. The upper flow pattern remains unsettled at least through the middle of next week and perhaps even through the end of this period. Guidance progs a stagnant pattern locally with the upper low or trough meandering and spinning just off to our northwest. Multiple s/w's in southwest flow aloft over our region will likely keep on and off shower chances persisting through the week. Underneath the more extensive cloud cover that anticipated, temperatures will be held in check close to normal but probably falling short of average for this time of year. Daytime values in the 50s and 60s can be expected with overnight temperatures in the 40s. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 647 PM CDT Fri May 3 2024 Terminals KABR,KATY,KPIR,KMBG Periods of MVFR cigs and MVFR/IFR vsbys will be possible under the banded rain shield that extends from south central South Dakota (KPIR) up through west central Minnesota (KATY). The whole band of rain is translating east-northeast, and is forecast to be clear of both KPIR and KATY by 06Z tonight. VFR conditions already ongoing at KMBG and KABR are forecast to persist through the TAF valid period. VFR conditions are forecast to establish at KPIR and KATY overnight and then prevail at those two locations through the rest of the TAF valid period. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Dorn SHORT TERM...Parkin LONG TERM...Vipond AVIATION...Dorn ####018006797#### FXUS62 KGSP 040216 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1016 PM EDT Fri May 3 2024 .SYNOPSIS... Dry and warm high pressure moves off the Carolina coast as a front approaches from the west then stalls over our region for the weekend. This front will result in periodic thunderstorms and showers starting today and lingering through the weekend. A general summertime pattern sets up early next week, which will likely support scattered thunderstorm development each afternoon. && .NEAR TERM /THROUGH SATURDAY/... As of 1010 PM EDT: Ridge axis still present over the SE Coast. Some disorganized bands of convection continue west of the Appalachians in the more unstable area upstream of the ridge, generally ahead of approaching shortwave. Little change in the pattern or vertical profiles tonight, such that a few hundred joules of MUCAPE will linger in southerly flow regime. Thus scattered showers and perhaps a few t-storms are expected to continue in the Smokies and Balsams, south to the Savannah Valley. Isolated cells recently fired up again near upper reaches of Lake Hartwell. At this point, main impacts from any storms are expected to be locally heavy rainfall. Outflow from earlier storms left behind a nearly saturated PBL in some spots, and some locally dense fog can't be ruled out in such areas overnight. With temp trends having stabilized and hi-res guidance having caught up, updated overnight T/Td and revised extent of fog per latest vsby guidance. Southerly flow is weak but should promote moisture advection into the lower Piedmont, possibly bringing fog and low stratus to those areas around dawn even if clouds inhibit radiation fog. Possibly more notably, the weak moisture advection may promote rapid development of convection around or after daybreak Saturday. Coverage should then increase for that reason and as forcing from the shortwave increases as the day continues. Instability and shear will remain on the weak side, while forecast profiles show an even more saturated atmosphere. This suggests and even less chance of strong to severe storms, with a slight uptick in heavy rain potential. That said, the overall flood risk remains low given the relatively dry antecedent conditions. Highs will be near normal due to clouds and precipitation. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 240 PM EDT Friday: The rest of the weekend looks active right into the first part of next week. A baggy upper trof overhead on Saturday night slowly lifts northeast with a short wave passage, and this bit of lingering forcing will be able to keep shower/thunderstorm activity on a slow wane into the early morning hours. Guidance suggests that it will never die off entirely, so the fcst retains some fairly high precip probs. That sets the stage for Sunday. Models show less forcing, but an uptick in the available buoyancy in the afternoon. That should make for a more thermodynamically-driven day, with better than climo coverage of showers and storms. Forecast soundings off the NAM show some pulse-severe wind damage potential with mid-level dry air and a shallow inverted-V, so it would not come as a surprise if it was a busier day than Saturday. A stronger short wave lifting northeast over the TN/OH Valley regions on Monday will continue to support diurnally-enhanced convection, so we continue with above climo precip probs. Temps look to be on the order of five degrees above normal. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 143 PM EDT Friday: The bulk of the medium range looks like a summer preview. After a baggy upper trof moves past Monday night, we should spend the remaining week underneath a low amplitude, relatively fast, WSW flow aloft. Within this flow, the model guidance shows a steady train of short waves moving through, mostly around peak heating each day, that will enhance our convective coverage each afternoon/evening. Overall, the air mass shows little change from one day to the next, as a wavy surface front will be strung out to our north in the WSW flow. Buoyancy will be modest and shear will be light, which suggests that chances for severe storms will be relatively low, but in such a pattern we eventually seem to manage to crank out a few pulse severe storms each day. Precip will be spotty and showery, which keeps the heavy rain threat at bay, but eventually there could be a few spots that start to see an increased risk of flash flooding, especially if a more coherent, stronger short wave comes along, such as what the GFS shows next Friday. Lots of uncertainty, though. Temps will remain in that 5-10 degree above normal range for most days, perhaps on the high side of that either Wednesday or Thursday, which one of those days might get a break in the wave train and thus reduced shower coverage and higher temps. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: -SHRA will approach KAVL and KAND this evening but chance of impacts small enough no mention is made in their TAFs. Multiple cloud decks above 070 will be seen tonight largely as a result of either convective debris or clouds forced by upstream shortwave. Sfc conditions will be moist tonight where precip outflow occurred Fri aftn, but otherwise low levels remain rather dry and extent of fog will be limited overnight especially given cloud cover. Some instability will persist overnight and new SHRA or even TSRA can't be ruled out after midnight near KAVL and the SC sites; S to SE PBL flow will serve as weak forcing. Restrictions are likely to develop around/after 12z as that flow replenishes sfc moisture and instability is realized, even if only as stratocu initially. Deep convection is possible as soon as mid-morning but more likely in the afternoon nearer axis of synoptic shortwave. Hence precip impacts are handled with PROB30s in the morning and TEMPO TSRA in the aftn. Any TSRA will be capable of torrential rain and so did not shy away from IFR vsby/cigs therein. Winds generally will remain southerly. Outlook: Enhanced moisture will combine with a weak/stalled front through early next week, resulting in a period of active/mainly diurnal convective weather each day. There will also be the potential for restrictions associated with widespread fog and/or low clouds each morning. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...RWH/Wimberley SHORT TERM...PM LONG TERM...PM AVIATION...Wimberley ####018004507#### FXUS63 KILX 040218 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 918 PM CDT Fri May 3 2024 .KEY MESSAGES... - Near daily chances for showers and thunderstorms over the next week as a series of fronts advance across the region. The Tuesday through Wednesday period looks particularly active, with medium confidence in thunderstorms capable of producing all severe weather hazards. && .UPDATE... Issued at 917 PM CDT Thu May 2 2024 The surface ridge axis has made eastward progress into Illinois this evening, helping to nudge high clouds eastward into Indiana as well. The back edge of the clouds is mainly covering counties along the Indiana border as of 9 pm, with additional clearing expected in the next few hours. Light and variable winds are expected overnight, under the weak pressure gradient. The main concern is for a possible need to expand the patchy fog across more of our counties than just our far southeast 6 counties south of I-70. There doesn't appear to be enough support in the high res guidance at this point to do that, so will leave the fog coverage as is. Only minor updates were done to sky and wind grids. The remainder of the forecast database remains on track. Shimon && .DISCUSSION... Issued at 127 PM CDT Fri May 3 2024 Current GOES WV imagery depicts a strong upper-level low positioned over western Ontario with more subtle shortwave energy ejecting out of the Great Basin. Model guidance remains in excellent agreement that shortwave energy lifts into the Northern Plains and Upper Midwest regions overnight, ultimately helping to force a synoptic cold front into western Illinois Saturday afternoon. A plume of low-to-mid 60s dewpoints is progged to advect northward ahead of the cold front, and SBCAPE values should be able to achieve 1000-1500 J/kg with CINH eroding in the presence of steep 0-3 km lapse rates (> 7.5 C/km). This all adds up to likely (> 60% chance) thunderstorm development Saturday afternoon along and ahead of the cold front. Coverage of Saturday storms could be limited by somewhat underwhelming deep-layer shear profiles, with much of the area at or below 30 kts in the vicinity of the cold front. Updrafts may struggle to become organized or struggle to stay organized, especially some of the early updrafts, and recent CAMs hint at this as well. Nevertheless, CAPE/Shear profiles are just good enough to support the potential for an isolated severe hail and wind threat. As storms move toward and east of I-55 Saturday evening, the severe potential should gradually fade. This will largely be due to the loss of daytime heating and the lack of a LLJ to help augment instability. This thinking lines up well with SPC's Day 2 Marginal Risk, which ends the threat near the I-57 corridor. Flooding should not be a concern with the Saturday storm event. NBM Mean QPF is around 0.25", and this guidance only offers a 10% chance that rainfall exceeds 0.75", which is well below 3-hour flash flood guidance. The rest of the weekend through Monday should be fairly low drama, with the main frontal zones displaced just to our south. Attention quickly turns to the Tuesday - Wednesday timeframe as persistent, deep southwest flow envelops the region ahead of an elongated upper-level low. While we're running lean on details at this timeframe, the synoptic pattern (kinematics/thermodynamics) being modeled supports a multi- day severe weather threat across portions of the Plains and Midwest. This strong signal in the global models is also reflected in the analogs and machine learning tools for severe weather potential. MJA && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... (For the 00z TAFs through 00z Saturday Evening) Issued at 711 PM CDT Fri May 3 2024 VFR conditions should continue through most of the forecast period, though conditions will likely deteriorate locally along and west of I-55 near the end of the period as a broken line of thunderstorms develop with a cold front. Variable, but predominantly northeast, light winds will veer to southerly between 13z and 16z with some localized stronger gusts (along with heavy rain, small hail, lightning) possible with the line of storms. Bumgardner && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$