####018009967#### FXUS63 KLMK 040145 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 945 PM EDT Fri May 3 2024 .KEY MESSAGES... * Isolated shower and thunderstorm possible this afternoon. Slow moving storm motion and moderate to heavy rain expected with any storm. * Showers and thunderstorms will be more scattered on Saturday, though forecast confidence in exact timing and coverage remains low. * Increasing potential for strong to severe thunderstorms and flooding next Tuesday through Thursday, though confidence in details is still low. && .UPDATE... Issued at 944 PM EDT Fri May 3 2024 As of 0130z, WSR-88D continues to show a few lingering isolated showers and thunderstorms, mainly over the Bluegrass. Weak sfc low and associated inverted sfc trough will continue to push east. Given the rain from this evening, high PWAT values around 1.50" and dew points in the low/mid 60s some patchy fog as well as drizzle associated with low stratus is possible during the overnight. Only made a few minor adjustments to the grids and the forecast to account for the patchy fog and updated PoP grids to account for some isolated light rain and or even a possible brief rumble of thunder. && .SHORT TERM /THROUGH SATURDAY/... Issued at 328 PM EDT Fri May 3 2024 ========== This Afternoon ========== The cold front is located just north of the Ohio River this afternoon, with our area within the warm sector of the system. Mostly cloudy sky cover has kept temps cooler than in previous days, with highs so far in the low 70s. However, the airmass is muggy enough to develop some marginal instability, with ACARS data from SDF showing over 500 J/kg of MLCAPE. Convective temps are close to the mid 70s, so if we can reach another degree or two we could see isolated convection fire up along the front or in the warm sector. We are already seeing some showers redevelop down towards Bowling Green, as well as along the front closer to Huntingburg, IN. Probability of thunder for this afternoon peaks around 50%, so coverage will be mainly isolated, and not everyone will see a thunderstorm. For those that do see storm activity in the next few hours, moderate to heavy downpours will be expected thanks to the PWATs around 1.5 inches. Additionally, very weak flow and shear will promote unorganized and very slow storm motions in addition to the lightning threat this afternoon. ========== Tonight ========== Around sunset and into tonight, precip coverage will begin to diminish as our daytime heating is lost. The cold front appears to wash out tonight, leaving no real source of lift in place. However, those high PWATs will linger, so will need to keep at least a slight chance through the night. However, better chances for additional showers come in the morning hours. Temps will be mild tonight, with lows only reaching the low to mid 60s. With the muggy airmass in place, and saturated grounds from recent rains, there should be a good chance for low stratus and fog tomorrow morning. After sunrise, stratus and fog will burn off. ========== Saturday ========== Another weak mid-level impulse should lift northeast from the south into the region tomorrow morning. This will bring additional rounds of isolated to scattered showers in the morning, with the greatest chances to the east of I-65. The forecast for tomorrow afternoon remains complicated in regard to shower and storm activity without much of a trigger mechanism in place. As mentioned earlier, the cold front will have washed out, leaving behind a moist and unstable airmass across the region. There will likely be some weakening mid-level vorticity left over from the morning impulse from the south, but overall the greater forcing will be up towards the Great Lakes later in the day. It'll be another muggy day, with dewpoints possibly reaching the upper 60s, with 12z HREF favoring 75-80% chance for dewpoints over 65F. PWATs don't appear to be as high as today, but still between 1.25-1.4" possible. However, sfc temperatures will be much warmer with highs hitting the upper 70s and possibly even the low 80s in some locations. This should lead to more potential instability during the afternoon, with forecast soundings suggesting between 1000-2000 J/kg of SBCAPE possible. Convection initiation tomorrow afternoon will probably be driven by differential heating boundaries or other mesoscale features present at the time. Due to this continued uncertainty, will continue with broad brush PoPs for the entire region. Severe thunderstorms are not expected due to another day of weak flow aloft. Storms that do form will be fairly slow movers, with storm motions generally less than 20 mph expected. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 328 PM EDT Fri May 3 2024 Synopsis...The medium-range forecast starts on Sunday by featuring an expansive mid-level ridge over the central and eastern US as mid- level shortwave energy lifts from Upper Midwest to Canada. Further west, a strong mid- to upper-level trough will move onshore from the Pacific eventually amplifying across the western two-thirds of the country by the middle of next week. The ensuing broad cyclonic circulation will allow the upper jet to stretch closer to the Ohio Valley while periodic shortwave energy rotate around the trough axis. As a result, there is a chance of organized, strong to severe storms for several days next week across the Lower Ohio Valley as the main trough meanders around the Plains. Model Evaluation/Confidence...Confidence in synoptic weather pattern has continue to increase as CMC/ECMWF/GFS deterministic models agree fairly well on the position and evolution of the main features (trough/ridge). On the other hand, confidence decreases in the timing and intensity of individual shortwave troughs embedded within the larger trough circulation impacting the ability to indicate the exact times of the severe weather risks. Nonetheless, the CSU and NCAR machine learning algorithms have been consistent at depicting, at least, low probabilities of severe weather for the Tuesday- Thursday timeframe. Sat Night - Sunday...A slight chance of showers and storms will continue Saturday night into sunrise on Sunday as a weak frontal boundary approaches the area overnight. The second half of Sunday morning and early afternoon looks drier as the diffuse boundary stalls close to the Ohio River. Another low chance of showers and storms might be in place late Sunday afternoon and early evening ahead and along the frontal wave provided that cloud coverage diminishes and solar radiation destabilizes the BL to yield CI once convective temperatures are met. Given the weak steering flow, mesoscale boundary interactions could play an important role for convective initiation and maintenance. Sun Night - Monday...An increase in shower intensity and coverage can be expected Sunday night into Monday morning as a southern- stream shortwave trough moves from the southern Plains to the Ohio Valley. GFS forecast soundings show increasing moisture profile with overall decreasing instability and warming mid-level temperatures. Therefore, there could be a chance of brief moderate to heavy rainfall with low thunder probabilities. This vorticity wave will push the stalled frontal boundary further north, so the shower coverage should decrease towards the afternoon and evening given the lack of any substantial forcing mechanism. Tuesday - Friday...As mentioned above, chances of strong to severe storms will be on the rise during the Tuesday-Thursday timeframe owing to the increasing shear associated to the incoming upper jet, the presence of moderately high instability values, and sufficient forcing provided by the periodic mid-level shortwave troughs. Although confidence in timing and details on type of severe risk are low at the moment, available medium-range CAM guidance (GFDL-SHIELD) hint at a multi-day overnight severe threat on Tue and Wed night with probabilities displaced further south for Thu night. A flooding risk cannot be ruled out either given the convective nature and duration of the weather events. && .AVIATION /00Z TAFS THROUGH 06Z SUNDAY/... Issued at 714 PM EDT Fri May 3 2024 Weak area of low pressure was located just west of KFTK this hour and will continue to move east-northeast this evening. Cold front remains northwest of the KSDF/KBWG/KLEX/KRGA terminals and will slowly move SE this evening. Cigs across the region have remained generally VFR with some tempo drops to MVFR in passing showers. Later this evening and into the overnight period, the cold front will slowly washout over the region leaving light winds and relatively moist boundary layer. Much of the guidance suggests that low clouds/fog/mist will likely develop with cigs falling through the MVFR range and then into the IFR range overnight. Vsbys look to remain mostly MVFR but IFR/LIFR vsbys may develop at KBWG late tonight. Cigs/vsbys should come back up in the 04/13-14Z range with skies eventually returning to VFR by late morning. For tomorrow afternoon, a bit more heating will take place and scattered showers and a few storms will be possible across the region. So will continue the VCSH mention in the new TAF package. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...BTN SHORT TERM...CJP LONG TERM...ALL AVIATION...MJ ####018006138#### FXUS61 KILN 040145 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 945 PM EDT Fri May 3 2024 .SYNOPSIS... Repeated rounds of showers and thunderstorms are expected through the weekend along with muggy conditions. Additional thunderstorms are possible into the middle of next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... A weak shortwave remains just upstream of the area, providing just enough forcing for some slow-moving showers to persist this evening. The flow through the troposphere is rather light, with nothing above 25 knots until reaching about 400mb and higher. The 00Z KILN sounding is nonetheless somewhat moist, with a precipitable water value of 1.37 inches. This will make for a mild night, with clouds and moisture keeping temperatures from falling too much from their current values in the 60s. Lows in the lower to mid 60s are expected. There may be a very gradual downward trend in shower coverage over the next few hours, but recent model runs do suggest some additional development in the southern ILN CWA (particularly the Cincinnati area) after 10Z. PoPs will thus be focused mainly on the southern part of the area at around daybreak, before precipitation is expected to become a little more widespread with heating tomorrow afternoon. Previous discussion > Light shower activity may continue late this afternoon/early this evening in the unsettled and weakly unstable environment across the Ohio Valley. While a few thunderstorms cannot completely be ruled out prior to sunset, persistent cloud cover and light rain earlier today has kept instability to a minimum. For the overnight, a weak cold front will attempt to drop in the from the north before stalling over northern Ohio. At most, only expecting a few degree temperature drop as some northeasterly flow tries to develop. However, winds could end up mainly remaining light and variable overnight since weak pressure gradient stays over the region. Some shower chances persist tonight and forecast lows are generally in the 60s. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... A weak stalled front is expected to lift north of the area on Saturday. Warm, humid conditions will be in place as southerly flow redevelops leading to highs near 80 during the afternoon. Instability should accompany the muggy conditions Saturday afternoon/evening bringing the chance for showers and thunderstorms. If a weak shortwave does end up moving through on Saturday, fairly widespread shower and thunderstorm coverage could develop. Severe chances remain low since shear is weak and DCAPE remains moderate to low in the moist, saturated sounding. Locally heavy downpours are likely since PWATs will be high. Additionally, brief gusty winds are possible in the strongest storms in the this summer-like setup. Shower/storm chances continue on Saturday night due to the possible development of an upper level shortwave and the approach of a cold front to the northwest. Brief, locally heavy rain remains the biggest threat since instability and shear are weak. Southwesterly winds persist along with warm and muggy conditions. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... A wet period is indicated as persistent moisture advection couples with waves of low pressure. Relatively slow moving systems will allow showers to linger, with brief dry interludes separating batches of showers. Precipitable water remaining above an inch will be feeding the showers. For Sunday, the first wave of low pressure will be tracking to the Great Lakes, resulting in widespread showers and a few thunderstorms. Much the same can be expected for Monday, though most showers may shift south, closer to a disturbance over the Southern Appalachians. A relative lull in precipitation is forecast for Tuesday as high pressure builds in between disturbances. Two more potent waves of low pressure could impact the region on Wednesday and Thursday. There should be a better chance for severe thunderstorms as stronger winds enhance storm strength and structure. Showers and thunderstorms may linger on Friday as another disturbance crosses the Appalachians. Temperatures are likely to stay above normal through the long term, with some fluctuation with respect to advection around weather systems. Highs will generally be in the mid 70s to low 80s Sunday through Thursday, before readings slip to the upper 60s to mid 70s on Friday under a modest decrease in geopotential heights. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... Generally VFR conditions are expected to start the TAF period, but some brief MVFR ceilings or visibilities will be possible as some rain showers continue to impact the area. There will be a gradual diminishing trend in shower coverage over the next few hours, with light winds settling into an ENE direction. By morning, ceilings are expected to lower to the MVFR range, with most TAF sites expected to go below 2kft. Some patchy MVFR visibilities are also possible in the early morning hours, but the thick cloud cover makes this somewhat uncertain. Some additional showers will be possible in the morning, though the chances are on the lower side, and this is not included in the TAFs. However, showers will become more likely again tomorrow afternoon, so all TAF sites have VCSH and then -SHRA. Thunderstorms are not out of the question either. Prevailing ceilings will lift to VFR by this time, with southeasterly flow of 10 knots or less. OUTLOOK...Thunderstorms are possible at times each day from Sunday through Wednesday. MVFR conditions are possible Sunday morning and Monday morning. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Campbell NEAR TERM...Campbell/Hatzos SHORT TERM...Campbell LONG TERM...Coniglio AVIATION...Hatzos ####018008206#### FXUS61 KPHI 040147 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 947 PM EDT Fri May 3 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 TODAY/... 9:45PM...The biggest change to the forecast was made to reflect ongoing conditions for the next several hours. The marine stratus has continued to dwindle over the area tonight, now only confined from around Philadelphia and across the Delmarva. Elsewhere, just some higher clouds remain to at times clear skies. As a result, have updated sky grids and also noted potential marine fog tonight (mentioned in marine section below). Otherwise, forecast remains on track with the previous discussion below: The current forecast continues to remain challenging due to pesky marine layer over the Coastal Plain. An expansive ridge of high pressure is building into eastern Canada with the southwestward periphery of this feature extending back into the Mid-Atlantic. In fact guidance actually depicts this feature strengthening slightly over our area during the next 24 hours. Meanwhile though, this ridge has resulted in easterly flow that has brought in a low deck of some marine stratus into much of NJ, DE, and even extending at times into portions of eastern PA. Finally, there is a frontal system that's approaching from the west with some showers however, it will take some time for these showers to get into the area over the weekend as it runs up against the ridge in place. The upshot of all this is that skies are variable across the area with the marine stratus eroding back to the east while high cirrus continues over western areas. Regardless, it will remain precip free though through the evening. Overnight, however, shortwave energy will ride over the top of the upper level ridge centered over the east and help to push showers from the west closer to the region. This could bring a few light showers into parts of Delmarva and eastern PA by daybreak. Otherwise, clouds thicken through the night with lows getting down mainly into the upper 40s to around 50. For Saturday, low pressure moves eastward towards the Great Lakes driven by an advancing upper level trough. As this occurs, showers well ahead of it will continuing to try making inroads into our area while running up against the stubborn surface high that will be slow to move out. The upshot is some scattered showers will likely make it in at times, especially over eastern PA and Delmarva and especially getting into the second half of the day (POPs here by late day generally 40 to 60 percent). Otherwise it will be a mostly cloudy and cool day with continuing easterly winds and highs only making it to the upper 50s to low 60s. && .SHORT TERM /TONIGHT THROUGH MONDAY/... Saturday night will featured continued marine flow from the east as the approaching front from the west washes out. Thus, expect areas near the coast to be mostly dry and cool, with a better chance of showers inland due to the nearby stalled front. Lows mostly in the upper 40s. Next, stronger front approaches from the west Sunday, but its approach looks slower, so have slowed the progress of higher POPs into the area. Looks like best chance of widespread showers is late day and at night Sunday night. With the marine layer likely to hold fairly firm, chance of thunder looks minimal, and severe weather risk appears zero. Highs 50s north, 60s south, perhaps near 70 far southern DE and adjacent parts of MD. Rain showers move out on Monday morning, though again opted for slower timing given trend. Marine layer looks like it is at least somewhat disrupted as flow turns westerly and a warm front tries to lift north, allowing temps to potentially rise to the 70s for most and near 80 southern DE/adjacent MD. Guidance now wants to generate some convection in the afternoon, and given the warmer and more humid air mass, its not out of the question we have a few stronger cells, but at this point there doesn't appear to be a significant severe wx or flood risk. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... Unsettled weather continues through the week ahead. The front that lifts north thru the area Monday doesn't get far, and looks to even slide back south a little Tuesday, though at this point still looks likely mostly 70s. Another approaching shortwave and proximity of the front could spark off a shower or t-storm, but right now looks like low coverage. Front lifts a little further north behind that shortwave Wednesday, allowing temps to rise a bit. With it remaining nearby and another front approaching from the north, the odds of some aft/eve convection increases a bit. Highs closer to 80. Guidance is trending towards the return of a marine layer behind said front for Thursday and Friday, with a cooling trend in temps. A passing wave may produce some better shower coverage Thursday as well, so we have highest POPs in the long term on Thursday. Friday trend is a little drier but still a marine influence. It should be noted that with the wavering front nearby all week and several weak waves, its possible the details of the forecast are notably different from how they currently appear, so check back for updates frequently. Guidance is very mixed presently. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Different conditions expected for each terminal tonight. For KRDG/KABE, expect VFR through 05-06Z, before becoming MVFR CIGs after 07-08Z. For KTTN/KPNE/KPHL/KILG, expect a mixture of VFR/MVFR CIGs through 07-08Z, before becoming MVFR CIGs after 08-09Z. For KMIV/KACY, expect MVFR CIGs through 05-06Z, becoming IFR CIGs after 06Z. East winds around 3-8 kt. Low confidence, especially with the timing of lowering ceilings. Saturday...Mainly MVFR for all terminals. There is indication a brief period of VFR CIGs are possible during the afternoon for all terminals except KMIV/KACY. Otherwise, just some scattered showers. East-Southeast winds around 8-13 kt. Moderate confidence. Outlook... Saturday Night through Sunday Night...Restrictions expected with showers moving through, with CIGs as low as IFR possible. Best chance of showers is late Sunday/Sunday night. Monday through Wednesday...Primarily VFR though some restrictions possible with any showers. 20-40% chance of showers through this period. && .MARINE... The Small Craft Advisory has been extended for the ocean zones from Cape May to Fenwick Island until midnight due to seas around 5-6 feet. These conditions should continue to diminish through the overnight hours with winds diminishing to 10 to 15 knots and seas around 3 to 4 feet. Little change is expected on Saturday. There is the potential for some dense marine fog early Saturday morning especially south of Little Egg Inlet, otherwise, just mostly cloudy skies are expected. Outlook... Saturday night through Wednesday...No marine headlines anticipated. Showers/thunderstorms possible on the waters Sunday through Sunday night. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until midnight EDT tonight for ANZ454-455. && $$ SYNOPSIS...Fitzsimmons/Hoeflich/RCM NEAR TERM...DeSilva/Fitzsimmons/MPS SHORT TERM...RCM LONG TERM...RCM AVIATION...DeSilva/Fitzsimmons/MPS/RCM MARINE...DeSilva/Fitzsimmons/MPS/RCM