Area Forecast Discussion
Issued by NWS Pittsburgh, PA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPBZ 190505 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 105 AM EDT Tue Mar 19 2024 .SYNOPSIS... Scattered snow showers are expected on and off through Wednesday with a crossing upper trough. Dry weather is then expected to return as temperatures gradually warm through the end of the week. && .NEAR TERM /THROUGH TODAY/...
-- Changed Discussion --
KEY MESSAGES: - Minor snow accumulation from Pittsburgh north. - 1-2" is possible with a localized 3 inch total in the ridges. ------------------------------------------------------------------- Updated PoPs to continue to reflect the batch of moderate snow showers pushing southeast across the region. Webcams and observations are showing a quick accumulation on area roadways and visibility down to a half a mile as it moves through. Overall forward motion is pretty quick which is helping limit accumulation, but still resulting in slick, snow covered roads... Snow shower coverage has been reinforced in the early overnight hours despite the loss of instability as a surface trough slides south across the area. This is resulting in minor accumulation especially in any areas where snow showers persist, primarily north of Pittsburgh as the surface cools. Probabilities are showing roughly 50% to 70% for an inch of accumulation in the counties along I-80 and in the higher terrain. In the ridges, 1-2" is expected with aid from upslope flow. Given the instability and upslope component, they may be an isolated 3 inch amount in the higher terrain from this snow shower event.
-- End Changed Discussion --
&& .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... KEY MESSAGES: - Scattered snow showers Tuesday and Wednesday with best chances for I-80 corridor. - Light accumulation possible. - Potential for strong wind gusts Tuesday night - Wednesday. - Low RH and elevated winds possible for Tuesday. ------------------------------------------------------------------- The upper trough axis gets an assist from a trailing shortwave and pushes out of the area on Tuesday allowing surface ridging to briefly build from the south. Another upper wave dives out of the Great Lakes later Tuesday and associated low pressure will slowly meander by to our north Tuesday into Wednesday. The best forcing and moisture will remain off to our north with low end snow shower chances mainly north of I-80 as ridging keeps the rest of the area dry through the daytime hours. A surface trough will sag through the area Tuesday night with vorticity advection streaming along with it and bring snow shower chances further south into the PA and WV ridges overnight with the probability for measurable snowfall highest in the WV ridges at 50% to 60%. This stands to be the best area with snowfall chances. In addition, outside of areas that get the heavier snow showers such as the lower elevations and south of I-80, expect drier air to infiltrate the areas in OH and WV and into some of SW PA. This will lead to low RH and elevated winds. An SPS will likely be needed for Tuesday afternoon. Colder air aloft moves in on Wednesday as the upper trough sags south with several shortwaves rounding its base. Low level lapse rates will steepen as a result and with the passage of a cold front, we`ll see snow chances continue on Wednesday again primarily for the I-80 corridor with the best moisture. Forecast soundings show some marginal instability with ensemble probability of >50 J/kg around 50% to 70% there, so the potential for some heavier banded snow showers is there and supported. Given the unfavorable diurnal timing and higher March sun angle, would be tough to accumulate efficiently on surfaces and result in more of a visibility concern, but any showers with higher rates may overcome the warmer ground and put down a quick accumulation. That said, the higher end of the distribution for snowfall totals seems reasonable for Wednesday, but it will be a day where the higher totals are localized to areas that see heavier snow showers, most likely north of Pittsburgh. Wind gusts will also increase with the passage of the front as the gradient tightens with highest gusts expected on Wednesday. Ensemble probability of exceeding 30 mph gusts is 80-90% areawide and will have to monitor the WV ridges for potential wind headlines with probabilities of advisory criteria increasing for Wednesday where gusts to 40-50 mph are possible. && .LONG TERM /THURSDAY THROUGH MONDAY/... KEY MESSAGES: - Below average temperatures Thursday rebounding to near normal for the weekend. - Rain/snow chances return Friday. ---------------------------------------------------------------- By Thursday, the upper trough pivots out through Nova Scotia as a brief bout of surface ridging noses in from the north. This should shut off any lingering lake effect precipitation Thursday morning and return dry weather for a day. A few ensemble members linger the trough a bit longer which keeps low probability snow shower chances around into the late morning on Thursday, but any additional accumulation would be minimal. Things then become a bit more uncertain with timing and strength of a flat shortwave sliding through the Great Lakes on Friday in relatively zonal flow returning the chance for snow showers mainly for the I-80 corridor and north. Lack of injection of cold air ahead of it with the progressive nature of the wave should keep any accumulation on the lower side. Going into the weekend, a southern stream shortwave slides through the Southeast and attempts to phase with the northern wave. Low pressure looks to develop across the Southeast and turn up the coast. The most likely ensemble solution at this time is a phasing offshore of New England keeping the low out of our hair, though a low probability chance exists for quicker phasing which would result in higher precipitation chances continuing from Friday into the first half of Saturday. Models and ensembles seem to also provide a bit of consistency to the Sunday and Monday forecast bringing in high pressure to the area with the potential of a few upslope showers. && .AVIATION /05Z TUESDAY THROUGH SATURDAY/... Snow shower coverage and intensity has begun to wane with loss of daytime heating. However, the crossing trough may help to reinvigorate showers through the early overnight, primarily north of Pittsburgh. Falling temperatures may allow light accumulations overnight, though little more than a dusting is expected. As the boundary layer cools/moistens and the inversion lowers overnight, ceilings will drop slightly into MVFR. This will improve after sunrise with increased mixing and arrival of drier air. A few snow showers may linger north of I-80 past 12Z Tuesday, with dry conditions otherwise. Westerly wind will continue to gust 15-20 kts overnight. This will become more southwesterly and gustier by midday, with peak values of up to 25 knots. .Outlook... MVFR conditions may linger into Wednesday with a new shortwave and burst of colder air from the north. VFR returns Thursday as high pressure builds over Ohio. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ SYNOPSIS...Shallenberger NEAR TERM...22/MLB/Shallenberger SHORT TERM...MLB/Shallenberger LONG TERM...MLB AVIATION...Rackley/CL

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.