Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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298 FXUS61 KPBZ 301728 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 128 PM EDT Sun Jun 30 2024 .SYNOPSIS... Isolated showers and storms will continue to move ahead and along a cold front early this morning into early afternoon. Building high pressure will return comfortable dry weather for the first half of the week before an unsettled pattern takes hold to close out the week. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - Isolated showers and thunderstorms are possible with a passing cold front. - Cooler and drier weather expected tonight behind the front. ------------------------------------------------------------------- The cold front continues sagging south across the area in an environment in which instability is plentiful with up to 1500 J/kg MLCAPE, EBWD of 30-40 knots, and DCAPE up to 1100 J/kg. However, updrafts are struggling with vertical extent as low and mid level lapse rates are poor, and storms are really only growing closer to the higher terrain where orographic influences may be providing an extra nudge. A good amount of mid-level dry air has started to work in as noted on the 12 PIT sounding, so despite the arrival of better forcing, updrafts may be entraining dry air. With warm rain processes still dominant, any shower or storm will produce a quick burst of heavy rainfall with it (earlier storms had 3-4"/hr rainfall rates). Our window for development will continue over the next couple hours until the front clears the area, and the highest threat for any strong storms still appears to be south and east of Pittsburgh. Convection promptly ends with the passage of the front. We then finally get a push of drier air (dew points in the 40s upstream) as high pressure builds across the Great Lakes and reinforces northerly flow in the wake of the boundary. Clouds will scatter into early this evening save for north of I-80 where forecast soundings indicate that lake moisture under northerly flow will remain trapped beneath increasing subsidence. In addition, a passing upper wave looks to reinforce cloud coverage further south toward morning on Monday. Still, overnight lows will be refreshing dipping into the 50s/ (60-80% chance of upper 40s in the ridges and north of I-80). && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... KEY MESSAGES: - Drier air builds in with cooler temperatures. ------------------------------------------------------------------- Dry weather and below normal temperatures prevail with high confidence Monday and Monday night as heights begin to rise and high pressure builds east. In fact, latest HREF probabilities show most locations having a <30% chance of reaching 75 degrees, with the exception being urban areas (e.g., Pittsburgh metro) and portions of eastern OH south of I-70 where the probabilities for reaching 75 degrees are closer to 50%. Low temperatures Monday night dip into the low to mid 50s, roughly 7-10 degrees below normal for this time of year. && .LONG TERM /TUESDAY THROUGH SATURDAY/... KEY MESSAGES: - Dry weather continues Tuesday with warming temperatures. - Showers and thunderstorms expected Wednesday through the end of the work week with the return of a more active pattern. ------------------------------------------------------------------- Good agreement amongst the various ensemble clusters supports dry weather on Tuesday as ECONUS ridging builds. Temperatures begin to rebound as flow becomes more south of east and pushes highs back toward or a couple degrees above normal. By mid-week, ensembles break the ridge down and shunt it southward over the Southeast CONUS and Gulf Coast, leaving zonal flow over the Ohio Valley and lower Great Lakes while lower heights settle in upstream over the upper Great Lakes and Midwest. This patten is certainly more active than the first half of the week, promoting surface low pressure over southern Ontario that quickly tracks northeastward and leaves a trailing cold front sagging southward into our area late Wednesday into Thursday. There is some minor concern at this time that the zonal flow overtop what appears to be a slowing and weakening/diffusing cold front could lead to a setup where multiple rounds of showers and storms develop along said east- west oriented boundary in a moisture-rich environment (ensemble mean PWATs surpassing 1.75 inches), leading to training of thunderstorms and flooding rain potential. It`s too far out to say any of this with certainty, but I would like to see the pattern become a bit more progressive to prevent the front from slowing or stalling over the local area and put these concerns at ease. Additionally, machine learning continues to highlight some severe potential with this pattern as the front will initially be moving into a warm and moist airmass, though weak flow aloft resulting in limited bulk shear is helping to keep the overall threat low at this time. Still, this too will bare watching over coming days. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... As the front slowly crosses, convection may development towards LBE and MGW, utilizing some surface heating early this afternoon. However, confidence is still low that the terminals will be directly impacted. Hi-Res guidance suggest VFR conditions will continue to build between 18Z to 20Z for areas north of PIT. Daytime gusts will range from 20-25kt with post-frontal mixing of a tight pressure gradient. Stratocumulus decks may try to fill in late tonight/early tomorrow monring unde northwest flow; especially for DUJ/FKL. .Outlook... VFR is expected until a slow moving front sets up across the region Wednesday and Thursday. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...MLB NEAR TERM...MLB SHORT TERM...Cermak/MLB LONG TERM...Cermak/MLB AVIATION...Hefferan