Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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628 FXUS61 KPBZ 162350 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 750 PM EDT Tue Jul 16 2024 .SYNOPSIS... Severe potential south of I-70 early this evening will be followed by another risk for storms late tonight. Thereafter, a cold front will swing through, allowing a third and final chance of severe weather tomorrow. Damaging winds remain the primary threat. Seasonable weather will prevail Thursday and Friday before a weekend warm-up. && .NEAR TERM /THROUGH WEDNESDAY/... KEY MESSAGES: - Two independent chance of severe weather are possible late tonight and tomorrow afternoon (through Pittsburgh and points south and east). - The primary threat remains damaging winds. __________________________________________________________________ .. Evening update .. The last of the rain is moving out of the far southern ridges. Models are not hinting at much more activity until late tonight early Wednesday morning. An isolated shower can`t be completely ruled out, but with the sunsetting and no real good forcing until later tonight, it does not look likely. PoPs were updated to capture a quiet rest of the evening. Overnight temperatures and clouds were also updated with the latest hires guidance. .. Previous Discussion .. Save a brief reprieve behind the passing wave late this evening through the early overnight, another embedded weak low-to-mid level wave will pass in the flow overnight. This time, probabilities of at least 20kts of bulk shear are 20% to 40% in the I-80 corridor, and less than 20% elsewhere. CAPE will likely be in the hundreds and mostly elevated, but should any mature updraft develop, it will again be possible at collapsing into gusty winds at the surface, pending breaking a shallow surface inversion. The most likely time for this event will be around 4am to 8am. This remains the lowest probability of the three severe chances. Last, but not least, severe probabilities increase into the day tomorrow along and ahead of the passing cold front. With better synoptic forcing and an increasing gradient within the trough itself, the confidence in initiation is the highest in this period. Consequently, bulk shear probabilities increase to 50% to 60% of greater than 30kts, and CAPE will be in the 500 to 1500 J/kg range, but mid level dry air will drop off, decreasing downburst threats. Convective nature will resort to higher confidence in storms, but lower confidence in intensity. Current thinking reflects that damaging winds are still the primary threat from noon to 8pm with a secondary threat of hail. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... KEY MESSAGES: - A drier and cooler period will ensue through Thursday and Friday. _________________________________________________________________ Dependent on front progression speed, some storms may linger into the mountains of northern West Virginia in the early overnight period, but thereafter, dry conditions are favored. Low-level cold and dry advection will keep temperatures near or even a few degrees below average Thursday and Thursday night with valley fog chances. Stout mixing into the day on Friday under high pressure will result in temperatures near normal, and fairly low humidity. This will leave the area feeling comfortable for the last day of the work-week. Radiative cooling will also drop temperatures near normal. && .LONG TERM /SATURDAY THROUGH TUESDAY/... KEY MESSAGES: - Diurnal shower/storm chances increase slightly with increased moisture. ------------------------------------------------------------------- Rising heights Saturday/Sunday in response to increased troughing over the Central Plains may bring moisture back from the south, leading to increased diurnal precipitation chances, mainly southeast of Pittsburgh. This will also result in a warming trend through the weekend. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... The convection threat is largely over for the evening. A few isolated showers are possible mainly southwest of PIT this evening, but VFR conditions are expected to dominate at all TAF sites through the evening and into the early overnight period. Showers and a few embedded thunderstorms remain possible once again after 10Z or so, as a few hi-res models show development from the southwest. Ensembles continue to show high probabilities for MVFR ceilings arriving with this activity, with a period of IFR also possible mainly north of PIT. These ceilings will slowly lift as daytime mixing increases, possibly achieving low VFR by early afternoon. Another round of more concentrated showers and thunderstorms then arrives with a crossing cold front. Thunder timing remains problematic, and thus stuck with VCTS mention for now. These storms will be capable of brief IFR/LIFR visibility in downpours, as well as strong, variable wind gusts. Terminals northwest of PIT will be cleared by the cold front prior to 00Z, with a wind shift to northwest and breaking clouds. .Outlook... VFR returns Thursday through Saturday under building high pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Milcarek NEAR TERM...Milcarek SHORT TERM...Milcarek LONG TERM...CL/Milcarek/88 AVIATION...Cermak/WM