Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 030935 AFDCTP Area Forecast Discussion National Weather Service State College PA 435 AM EST Sat Dec 3 2016 .SYNOPSIS...
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High pressure will build in later today but slide quickly off to the east on Sunday. A weak frontal boundary passing through Sunday night will cause light snow in the north and rain or snow in the south. A storm with mainly rain may affect the area during mid- week, some mixed precipitation may occur at the beginning of that storm.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Low pressure over ME and Canadian Maritimes will move to the east and relax the NW flow - but not until late today and this evening. Expect more of the same through the daylight hours. Temps should rise a grand total of 3-5F today. The brisk west wind will continue. Still looking for an inch or less for accums on the higher ridges in the NW, and nil elsewhere. Most of what falls from the sky will just be a flurry or sprinkle.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
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Flow relaxes tonight as sfc ridge slides overhead for Sunday morning. Some decrease in cloud coverage is expected overnight, but it turns right around during the day on Sunday. High/mid/low cloud progression will darken things again wherever breaks/clearing does occur. The E/SE will stand the best chance for complete clearing. Temps will be cooler tonight without so much wind to keep us well-mixed. Biggest challenge in this cycle is what kind/how much precip falls Sunday night from the passage of a weak front. All the models and most of the GEFS members crank out 0.05-0.20 inches of QPF for Sun night as the feature is carried steadily through by mainly zonal flow. Most of the precip should be snow, but it is not likely to stick in many places SE of the Allegheny Front. Just the highest hill tops of the SE may get a dusting. For a few runs, a weakness exists in the QPF right through Central PA from W-E. This seems to be a disconnect between the moisture and the left-exit region of a 150kt jetlet which passes right over the state. Temps are marginal for accums, and QPF is light. Have drawn 1-2 inches across the nrn tier of counties. It is a nighttime event, and temps in the nrn tier are much more likely to be sub-freezing all night.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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There is decent agreement in bringing the SW US upper low up through the Ohio Valley on Tuesday as a shearing out shortwave and diffuse surface low. Unless cold air damming traps enough chilly air in the low levels to make for some freezing rain, the precip type with this midwest system looks to be mainly rain. Have raised POPs into the categorical range as it seems unlikely that we will get missed. The end of the week brings some model disagreement with the GFS/GEFS being faster than the ECMWF with the next large upper trof and frontal system. Either way, precip looks like a good bet around the Thu/fri period as all solutions eventually bring this trough through. So predictability is increasing, but timing issues remain. Best bet for precip at this point is mainly rain over the SE as decent push of warm air lifts ahead of the system, with a rain/snow mix further north where warm air will not infiltrate as much. Behind the trough, looks like a chilly weekend in store with a potential sharp dropoff in temps.
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&& .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... At 06Z satellite showing an extensive stratocu deck across most of Pa associated with an low pressure over Southern Quebec. CIGs ranging from low MVFR at KBFD/KJST to between 4-5kft at the lower elevation airfields, including KIPT/KMDT/KMDT. The main aviation concern this morning will be at KBFD/KJST, where moist WNW flow forced to ascend the Appalachians will create borderline IFR CIGs and occasional snow showers. Downsloping flow will result in progressively better conditions further east, with MVFR cigs likely at KUNV/KAOO and VFR conditions at KIPT/KMDT/KLNS. High pressure approaching from the west will cause snow showers to diminish across the Western Mtns later today. However, model soundings still indicate persistent MVFR CIGs at KBFD/KJST through this evening. WNW winds should continue to gust to around 20kts today, then expect diminishing winds this evening as high pressure builds in. Outlook... Sun...Light snow/reduced vis possible at night, mainly NW Mtns. Mon...No sig wx expected. Tue...Mixed precip/low CIGs possible, especially late. Wed...Lingering low CIGs possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...Gartner/RXR AVIATION...Fitzgerald

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