####018006604#### FXUS61 KPBZ 161451 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1051 AM EDT Fri May 16 2025 .SYNOPSIS... There is potential for strong to severe storms today and tonight as a cold front approaches. Drier and cooler conditions return Sunday through early next week. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - Convoluted environment today will maintain low confidence in the presence of storms, but moderate confidence in severe potential given initiation. - A decaying MCS in possible tonight somewhere in the Appalachians, but confidence in location is low. ------------------------------------------------------------------- The lack of overnight storms south of I-80 completely changes the severe forecast for today. Given CAM guidance before 12Z showed a worked over environment across the area, it poorly represents current conditions. So the forecast will heavily rely on initialization at and after 12Z. Given a look at the current wind field and satellite, there is some indication of a convergence zone in to low levels settling in across southwest PA, eastern OH, and the northern WV panhandle. In addition, there is a residual outflow boundary from overnight convection in the I-80 corridor. If an area was favored for convection, it would be along an east-west axis passing near the Pittsburgh area. Looking at the 12 sounding showing ~1400 MLCAPE and ~900 DCAPE, the atmosphere would be primed for severe convection, particularly if updrafts drive into and wet-bulb the 6km to 12km later. There intense updrafts in a high DCAPE environment would have a primary risk of damaging winds and hail. There is a chance the DCAPE is lower later in the day, though this would rely on upstream convection to contaminate the environment, which is still of moderate uncertainty. After initiation, would would expect the primary storm motion to be to the northeast as outflow combined with synoptic wind. If there is an area to watch for flooding, it would be on the south side of convection, where outflow would be fighting the synoptic wind field, resulting in training. Uncertainty snowballs tonight as convection will rely on two factors: 1) Where and if the environment has been tainted by daytime convection. 2) Where storms fire upstream during the day today. If todays storms put do an outflow, it is very likely overnight convection stays south of it. This boundary will be important in distinguishing the threat as scenarios range everywhere from no outflow to outflow far south of the area. The farther north and/or a lack of an outflow means higher severe chances tonight. Second, there is initiation today. The farther north storms in the northern Ohio Valley initiate today, the higher the chance our region is impacted by a progressive, decaying MCS. With both of these factors together, the best chances of severe tonight increases the farther south of Pittsburgh you go. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... KEY MESSAGES: - A cold front crosses the area, ending thunderstorm activity and ushering cooler and drier weather into the region. ---------------------------------------------------------------- Showers and storms depart the area to the east on Saturday as a cold front sweeps through the area, ushering in cooler and drier weather under deep-layer northwesterly flow. Showers could linger in the ridges through Saturday evening with weak upslope occurring in the wake of the front, but by overnight hours that activity too should wane, with temperatures then dropping into the low to mid 50s by early Sunday morning. && .LONG TERM /SUNDAY THROUGH THURSDAY/... KEY MESSAGES: - Cooler and drier pattern returns Sunday through Tuesday. - Precipitation chances return Tuesday into Wednesday with another low pressure system - Potential for heavy rain mid-week that warrants monitoring ------------------------------------------------------------------- Models have been consistent that troughing over the Great Lakes and northeast CONUS will maintain northwest flow over the local area Sunday into Monday, keeping temperatures seasonable and the weather dry through that time. Probability of precipitation increases again late Tuesday into Wednesday with a new low ejecting out of the Rockies and tracking east across the Plains. A few model scenarios note a stationary boundary straddling south of Pittsburgh with this passing low. If that scenario plays out, heavy rain could pose a threat for portions of the region around mid-week. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... A shortwave trough continues to track through the Ohio Valley region this morning. Capping overnight kept a lid on much of the region, with only a broken line of thunderstorms continuing to track along the far north impacting FKL and DUJ. The line of storms will be through FKL by 12z and very near DUJ before tracking east. The southern extent of this line will scrape past BVI but VFR is expected to prevail with a low probability of MVFR CIGs. Many other ports this morning will start the morning in VFR under largely clear skies. Scattered diurnal cu is expected to develop through the day. With the thunderstorms not developing as far south as expected early this morning, this will result in more destabilization later today as another shortwave crosses the region. Maintained a prob30 mention of thunder for most airports south of Rt 422, though considerable uncertainty exists in this scenario. Another round of thunderstorms, possibly an MCS, is expected to cross the region late this evening with a crossing cold front. Models differ on the northern extent of this potential, which could also be impacted by any afternoon convection. Included a prob30 for thunder for now until forecast details become more clear. Outlook... Patchy restrictions in scattered showers are expected Saturday and Saturday night under a crossing upper trough. VFR returns Monday under high pressure. Restriction and rain potential returns with a Tuesday warm front. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Cermak/Hefferan NEAR TERM...Milcarek SHORT TERM...Cermak LONG TERM...Cermak/Hefferan AVIATION...WM/AK ####018008870#### FXUS64 KHUN 161454 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 954 AM CDT Fri May 16 2025 ...New NEAR TERM... .NEAR TERM... (Rest of Today and Tonight) Issued at 954 AM CDT Fri May 16 2025 A frontal boundary remains oriented through the middle of the Ohio Valley southwest into NW Arkansas and NW Texas. A large occluded surface/upper low over western Wisconsin/eastern south Dakota is pushing this front very slowly eastward today into tonight. A large area of severe convection has been ongoing into southern Kentucky ahead of this front over northeastern Arkansas and western Tennessee. This is being forced by a weak shortwave and increasingly strong nose of a low level jet over those areas. The good news is that most guidance moves this forcing primarily to the northeast today. RAP13 wants to produce QPF well south of the earlier mentioned activity this morning into the afternoon hours. Based on 7 AM soundings (especially from WFO Birmingham), a very strong low level inversion is in place over the area. Believe our conditions are closer to the environmental sounding in Birmingham, AL than the Nashville, TN 7 AM sounding. Mainly, based on how much closer to the front is to Nashville, TN. RAP13, is also a outlier even from most new 7 AM model guidance. This very strong inversion and the displacement of the mid/upper level forcing to our north should keep convection from firing over northern Alabama and our TN counties today into the very early evening hours. Therefore, keeping similar timing with convective initiation over the area later tonight as did the previous shift. The main window for severe storms still as below: 1. Franklin (AL) NW Lincoln County (TN) - 10 PM to 2 AM 2. SW Lawrence County (AL) to Sewanee (TN) - Midnight to 3 AM 3. SE Cullman County (AL) to Fort Payne (AL) - 2 AM to 5 AM If mid/upper level forcing does arriver earlier, then supercells and a larger hail/stronger tornado threat could exist. However, that is not expected at this time. Cloudy conditions should continue much of the day with a few breaks here or there from time to time. Highs should still be able to make it up to the mid to upper 80s despite the cloud cover. Enough MUCAPE or SBCAPE (700 - 1500 J/KG) or slightly more in some guidance could linger ahead of the front over the area into the overnight hours (mainly before 3 AM). This CAPE does drop off as you go further SW in the area. However, strong shear continues to be shown ahead of the front and 0-3 km helicity climbs to between 200 and 350 m2/s2 as the forcing moves into the area during the timeframes mentioned above. Expect there could be some embedded supercells (producing large hail initially) that move into the area. Still thinking this will form into a more widespread damaging wind threat with a few tornadoes possible. Though very low confidence, a strong tornado threat does look possible mainly in our TN counties and west of the I-65 corridor (unless instability drops off quicker overnight). && .SHORT TERM... (Tonight through Sunday) Issued at 303 AM CDT Fri May 16 2025 Morning update: SPC has expanded the Enhanced Risk (level 3 of 5) to cover far NW portions of AL and southern middle TN. Confidence has increased that severe storms will not enter the area until 10pm or after tonight. Damaging winds remain the primary concern, especially along any bowing segments that may occur. Confidence in the threat for hail and tornadoes remains low. Previous discussion: There is a low-medium chance of strong to severe storms tonight into Saturday morning- bringing threats of damaging winds, hail, and tornadoes. Primary timing for these threats is 10 PM tonight through 7 AM Saturday, which we have medium confidence in. As the aforementioned upper level low continues further into the Great Lakes region, a cold front is forecast to stem southwestward through the OH River Valley and into the Deep South. High pressure in the Gulf will allow southwesterly flow to advect moisture into the area ahead of the cold front arriving in the TN Valley. An increasing LLJ (~60 kts) will provide additional forcing for convective development ahead of the front. Current thinking is that it will be supercellular in storm mode NW of our area before upscaling into a linear system as it continues into the Tennessee Valley. Our mean wind, if relatively tall storms are realized, is around 50 kts. Therefore, storm motion will be fast as it continues southeastward through the area. This, combined with DCAPE values of 800+ J/kg as well as steep mid level lapse rates allows us to continue advertising strong to damaging winds as the primary threat with hail as a secondary threat. Tornadoes will also be possible as low level streamwise vorticity continues to appear in model hodographs. Outside of the severe threat, we also have a low threat of flash flooding. Model sounding PWAT values are ranging from 1.5-1.7", which is near or above the 90th percentile per BMX sounding climatology. However, with fast-moving storms, this will continue to be a low threat. We will be having to monitor the capping inversion and if we are able overcome it as model soundings have consistently shown a weak to moderate cap over the area. Another complication is that CAMs continue to have slight disagreements in timing- with some pushing it later than what we currently have forecast. If this were to occur, we would have less instability to work with as we lose diurnal heating deeper into the overnight hours. By Saturday morning, the line of storms should move out of the area to the southeast by around 12Z. Dry conditions are forecast to pursue the area behind the front with mostly clear skies, however, this will be short lived as medium to high rain chances (40-70%) return to the area by Sunday. This will be due to the previously mentioned frontal boundary lifting back northeastward- causing a potential MCS as it moves across the area. While there is still model disagreement in our potential environment, there could be enough instability to warrant another low end severe threat with damaging winds as the primary hazard. Be sure to check back in for updates on this system through the weekend. && .LONG TERM... (Sunday night through Thursday) Issued at 1048 PM CDT Thu May 15 2025 Shower/thunderstorm chances are forecast to decrease Sunday evening into the overnight hours as the aforementioned potential MCS continues northeastward. However, low chances (30% or less) of rain remain north of the TN River as the front is forecast to stall out to our NE through the early part of the week. Another upper level low is forecast to move through the Central Plains early in the week as well- forcing a weak ridge over the Tennessee Valley to continue eastward and PVA to take over the area by Tuesday. This will allow increasing shower/storm chances over the area, once again, as we continue to remain in an active pattern through the long term period. Since this is several days out, there is still uncertainty in specific placement of the potential trough through mid week and subsequent threats for strong storms. Therefore, we continue to encourage everyone to check back in for updates with this active weather pattern we remain in. Otherwise, we will generally cool through this period as highs go from the 80s on Monday to the 70s on Thursday. Overnight lows are forecast to drop into the 60s-70s. && .AVIATION... (12Z TAFS) Issued at 556 AM CDT Fri May 16 2025 VFR conditions were observed for much of the local area at issuance. A brief period of MVFR CIGs is forecast by 14Z, but this should last 2-3 hours at most. VFR conditions are then anticipated by around noon once again. Breezy conditions with gusts to 15-20 knots are possible through the day at times. A cluster of storms is slated to move through the region later this evening and overnight, bringing the potential for damaging winds, hail, and a few tornadoes. Lower CIGs and VIS to at least MVFR are also expected in the heavier storms. The other concern by about 0Z this evening will be LLWS from the southwest between 40-50 knots which may persist until about 8-9Z or so. Outside of this and storms, southwest winds generally around 5-10 knots with gusts up to 20 knots are expected tonight. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...KTW SHORT TERM....HC LONG TERM....HC AVIATION...26