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FXUS61 KPBZ 190733 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 333 AM EDT Sun May 19 2024

SYNOPSIS
High pressure will provide mainly dry weather and a warming trend in temperatures through Tuesday. Showers and storms return Wednesday through late week.

NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:

- Morning fog possible, followed by mostly sunny skies.
- Above-normal temperatures continue as a warming trend begins.
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Latest RGB satellite composites confirm fog is beginning to develop in area river valleys. Expect this trend to continue through sunrise as fog potentially becomes more widespread, with the most dense pockets focused along rivers and in areas where the heaviest rain fell earlier in the weekend. Fog should dissipate rather quickly after sunrise with the onset of diurnal heating/mixing. An upper ridge building overhead in the wake of the Friday/Saturday trough should keep winds light and temperatures warm throughout the day, with highs climbing into the low to mid 80s across much of the area this afternoon, around 10 degrees above normal for this time of year.

Mostly clear skies, light winds, and above-normal temperatures continue straight through tonight with lows expected to remain in the mid to upper 50s across the area.



SHORT TERM /MONDAY THROUGH MONDAY NIGHT/
KEY MESSAGES:

- Dry weather can be expected through Monday night.
- Temperatures continue to climb to 10-15 degrees above normal.
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Dry weather is still forecast for the majority of the region through Monday night as the upper ridge remains in place overhead. Temperatures continue to warm as well, reaching the mid to upper 80s during the afternoon, roughly 10-15 degrees above normal for this time of year. Lows Monday night remain in the 60s for most areas outside of the ridges, where mid to upper 50s remain likely.

LONG TERM /TUESDAY THROUGH SATURDAY/
KEY MESSAGES:

- Dry and quite warm Tuesday.
- Rain chances return for Wednesday and Thursday, with some potential for strong thunderstorms.
- Seasonable temperatures and lower rain chances are expected Friday and Saturday.
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Dry weather prevails through Tuesday night as the upper ridge slowly works its way off of the Atlantic Seaboard. A very weak shortwave moving through its northwest periphery traverses the lower Great Lakes Tuesday afternoon and could bring just enough lift to support a few isolated showers and storms across NW PA and NE OH. This is reflected in the forecast with low-end PoPs (~20%) primarily north of I-80 and across our northernmost tier of Ohio counties. The bigger impact on Tuesday will be temperatures, with plenty of sunshine and dry antecedent conditions pushing values further into the upper 80s and potentially closing in on 90 degrees in some areas. Ensemble probabilities for highs on Tuesday reaching 90+ degrees are >50% in river valleys and urban areas at this time. It's not out of the question for some of the "cooler" daily records (86 at DUJ, 91 at PHD, and 92 at PIT/MGW) to be within reach.

While models continue to show some minor differences with the strength and timing of a series of troughs ejecting from the central Rockies across the Plains during the middle part of the week, the larger overall signal generally favors a deepening upper low over the Upper Great Lakes Wednesday morning and a second shortwave trough subsequently rotating around its southern periphery and across the lower Great Lakes Wednesday night into Thursday. The result of this pattern is increasing chances for showers and thunderstorms both Wednesday and Thursday across the local area, with the highest probabilities (currently 50-70%) coincident with the latter shortwave timing Wednesday night and Thursday morning. We will continue to watch for the potential for severe weather with this system, as CIPS/CSU severe guidance continues to show some potential, particularly on Wednesday. Temperatures on Wednesday, while still expected to run above normal, may be knocked down a few degrees compared to Tuesday due to the increasing cloud cover and coverage in showers and storms.

Model divergence increases as we look beyond the cold front passage on Thursday, but it does appear that the passage of additional weak shortwaves may provide lower-end chances (20-40%) for rain straight through the weekend, with temperatures returning closer to climatology during that time.

AVIATION /07Z SUNDAY THROUGH THURSDAY/
Not much change from the prior forecast with fog still likely near daybreak for many ports under clear skies and calm winds with antecedent saturated soil moistures. Probabilities of less than one mile visibility are highest for river valleys (roughly 60%) and generally north of Pittsburgh (roughly 40%).
Temperatures are already nearing dew points for most locations.
Patchy periods of MVFR remain possible at all ports with generally 50% to 70% probability.

With continued mostly clear skies and light to calm winds under high pressure today, no restrictions are likely after fog clears shortly after sunrise. Patchy fog remains possible tomorrow night once again, but mainly after 06Z and east of Pittsburgh.

Outlook
VFR and dry weather with high confidence are expected Monday and Tuesday under the influence of high pressure. Precipitation chances and associated restrictions return Wednesday.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...None.
OH...None.
WV...None.

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