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FXUS61 KPBZ 100611 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 111 AM EST Sun Dec 10 2023

SYNOPSIS
Rain will continue through most of Sunday as a cold front approaches and crosses. Rain will change over to snow Sunday night. A few inches may accumulate on the ridges into Monday. It will be a chilly Monday as temps won't get above freezing.

NEAR TERM /UNTIL 6 PM THIS EVENING/
Made some minor adjustments to PoPs and timing based on radar trends and a hi-res model blend. Temperatures are also running a bit above the previous forecast in the deep southerly flow ahead of the front. Made appropriate adjustments, resulting in a slight upward bump in overnight lows, especially east of Pittsburgh.

Previous discussion...
The main period of rainfall will still occur in the tonight/Sunday morning period. This is associated with elongated trough extending into the Mississippi River Valley and a cold front crossing into the Ohio River Valley. Heavier rainfall potential has decreased significantly due to dry air over the Southeast and over the Great Lakes. According the grand ensemble of Hi-Res model guidance, probability of a half inch of rain is 80% for areas southeast of Pittsburgh by Sunday evening and only 10% for 1.00 inch of rainfall. Therefore, the Marginal risk for Excessive Rainfall issued by the Weather Prediction Center has been removed for our County Warning Area (CWA) and river rises will likely not be impactful.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/
Key Message: Rain changing to snow Sunday evening with few inches of accumulation in the mountains and north of I80. A winter weather advisory has been issued for eastern Tucker Co.
in WV.

Precipitation type will likely change from rain to snow late Sunday evening from northeast to southwest with the passage of the cold front. Snow character will start out as wet as model soundings depict a deep layer stable air extending from 850mb to 500mb and temp profiles hugging the -10C isotherm. Models have been consistent that 2 to 5 inches of snow will accumulate in eastern Tucker over the last 48 hours. Probability of 2 inches is over 90% for eastern Tucker, 65% for 4 inches of higher. With low probabilities for 6 inches (33%) or higher, decided to issue a Winter Weather Advisory opposed to a Winter Storm Warning. If confidence increases, the ridges of the Laurel Highlands and eastern Preston county may be included in the Winter Weather Advisory in the next forecast update.

With prevailing northwest flow and passing upper-lvl trough over the Great Lakes, training convection snow bands may create an additional 1-2 inches north of Pittsburgh early Monday morning through early Monday afternoon. Ridging and westerly flow will like diminish the chances of snow by 7pm Monday.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
Ridging over the Central Appalachians will likely clear the sky Monday night. Therefore early morning lows on Tuesday will still dip into the 20s. If gusty winds remain elevated, apparent temperatures could drop into the single digits in the higher terrain.

Dry weather will then take hold for the remainder of the extended period, with quasi-zonal flow Tuesday and Wednesday eventually giving way to strong ridging over the Eastern CONUS. Temperatures will moderate close to normal in this pattern for Tuesday. A weak and likely dry frontal passage Wednesday may drop temps slightly below normal again for Wednesday. The rising heights will create a slow warming trend Thursday and Friday, perhaps to above-normal levels.

AVIATION /06Z SUNDAY THROUGH THURSDAY/
Dry air out ahead of the approaching cold front and associated swath of rainfall will likely dissipate a bit as it moves in resulting in only some MVFR conditions but other terminals will see IFR or below at times through dawn as the column of air moistens near the surface. Expect MVFR and some IFR cigs but rainfall should be heavy at times to produce some MVFR and IFR visibility at times. Conditions should begin to improve a bit as the cold front approaches later today. Winds through dawn will increase as well with some LLWS likely as well. Some gusts up to 25 knots are possible through dawn and into the coming day.

The cold front should begin to move through the forecast area by 18Z with gusty winds and plummeting temps for the last half of the TAF period. By Sunday night, expect showers to change to snow with another round of MVFR cigs and visibility impacts based on passing snow showers.

OUTLOOK
Restrictions in snow and rain into Monday at terminals close to the mountains. A return to VFR is expected Monday night and should persist through much of next week with building high pressure.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...None.
OH...None.
WV...Winter Weather Advisory from 7 PM this evening to 1 PM EST Monday for WVZ514.

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