Sunrise 6:14 AM   Sunset 8:19 PM Moonrise 2:57 AM   Moonset 2:08 PM

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FXUS61 KPBZ 030033 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 833 PM EDT Thu May 2 2024

SYNOPSIS
Dry and warm weather gives way precipitation chances Friday afternoon through this weekend. Cooler, but still above average temperature prevail Saturday and Sunday. Warm and unsettled weather continues next week.

NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
KEY MESSAGES:

- Dry with above normal temperatures continuing.

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High pressure and upper subsidence will maintain dry weather during the overnight period. Flow aloft will transition southwest and allow 700mb to 900mb temperature to remain steady and seasonably warm. This will limit potential for sharp radiative cooling while introducing increased cirrus cloud coverage; this will result in low temperatures remaining around 10 to 15 degrees above average.

SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/
KEY MESSAGES:

- Thunderstorms Friday afternoon and evening.
- Rain favored for most of the area through the weekend.

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As a disturbance approaches from the west, there is high confidence that a cirrus deck will progressively thicken throughout the morning and early afternoon. Diurnal heating will act to break the morning inversion and mix up into a layer of 850mb-700mb air nearly 11C to 14C above average for this time of year. This will allow high temperature to reach the middle to upper 80s for most of the area. Due to increasing cloud cover, the NBM high temperature for tomorrow was not adjusted upward any further. Forecast highs have the potential to break records (see climate section). Likewise, record low max temperatures may be broken Saturday and Sunday morning with persistent cloud cover not allowing for radiative cooling.

Rain chances have increased a bit earlier that the prior update with models suggesting that storms pop in surface- based instability despite dry low-levels with a fairly deep mixed layer. A the HRRR 25th and 75th percentile have between 400 and 1000 J/kg of environmental CAPE. Once parcels reach the LCL, a they will be able to utilize this to grow into showers/storms in the afternoon. Most guidance suggests that warm mid-levels will suppress updrafts to below about 500mb, but a small fraction suggest mid-level dry air may not be present (notably the NAM).
This would lend to low-probability of deep updrafts in the afternoon.

Convection is favored to wain overnight as instability is lost ahead of the surface trough. Nonetheless, rain will persist. Come Saturday, there is some suggestion the trough progression will come to a halt and allow rain to persist ahead of it, while precipitation may be harder behind it with mid- level dry air intruding. The positioning of the trough will have a great influence on the weekend weather. The current forecast favors rain in western Pennsylvania and northern West Virginia Saturday, while there is some uncertainty in eastern Ohio.
Probabilistic CAPE in western Pennsylvania ranges from 500 J/kg on the high end to none on the low end. Probabilities of thunder in western PA are 20% at best, with around a 30% chance in eastern Ohio and northern West Virginia.

There is good agreement the trough finally pulls through by at least Sunday. An area of maximized precipitation ahead of or just along the trough axis is favored; the susceptible is located in western Pennsylvania and the northern WV panhandle for now. Precipitation may be as high as 2" at any given area (mist likely in the aforementioned favorable region), or as low as 0.3". Right now the mean 48 hour rainfall around an inch area- wide. This does not raise any flooding concerns for now, but may warrant watching.

LONG TERM /MONDAY THROUGH THURSDAY/
KEY MESSAGES:

- Rain chances continue into early next week but more uncertainty lends lower confidence.
- Temperatures favored to remain above normal.
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A brief lull in the precip is favored late Sunday night into early Monday morning as upper ridging slides through and surface high pressure meanders on by. Uncertainty with its strength and timing due to ensemble differences in a passing upper wave to the north and another digging shortwave and associated low pressure moving across the Tennessee Valley lends lower confidence to the start of the next workweek, but regardless rain chances ramp back up later Monday. A stronger ridge and thus less rainfall is the most likely ensemble solution at this time, but a quicker breakdown of it could give us another decent shot of rain through Tuesday.
Due to aforementioned ridging, above average temperatures remain favored into next week. The amplified pattern continues into mid- week with unsettled weather in store.

AVIATION /00Z FRIDAY THROUGH TUESDAY/
VFR conditions and light winds prevail through tonight with thicker high clouds beginning to stream in from the west.
Mid-level clouds move in late Friday morning and afternoon while winds veer to easterly and then southeasterly. Scattered showers and thunderstorms are expected to develop late Friday afternoon and evening. Expect locally lower ceilings and visibilities, lightning, and possibly some gusty winds to accompany any stronger storms. Outside of convection, ceilings continue to gradually lower, with restrictions possibly settling in just beyond the current 24-hour TAF period Friday night as a more widespread coverage in rain showers is expected.


Outlook
Restriction potential will return Friday night and continue through Saturday, then again early next week as multiple disturbances cross the region.

CLIMATE
Some record high temperatures may be approached on Friday.
(* denotes current forecast temperature exceeds value)

Record High Year Pittsburgh 95 1887 Wheeling 90 1942 Morgantown 88* 1965, 2012 New Philadelphia 89 2012 Zanesville 91 1938 Dubois 84 2012

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

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