Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 170545 AFDCTP Area Forecast Discussion National Weather Service State College PA 1245 AM EST Mon Feb 17 2020 .SYNOPSIS... A weak upper level level disturbance in conjunction with a surface trough of low pressure could bring some areas of very light snow to the southern half of Pennsylvania this evening. Low pressure moving across the Great Lakes and it`s associated warm and cold frontal boundaries, will bring our next round of precipitation late Monday night into Tuesday. The precipitation should begin as a period of wet snow across the Central and Northern counties of the state with mainly rain expected elsewhere. Colder air will return for the second half of the week with below average temperatures. && .NEAR TERM /THROUGH TODAY/... High pressure building southeast from the Grt Lks will ensure dry weather for the rest of the night, with clearing skies. Low temperatures should range from around 20F in the northwest to around 30F in the southeast. Latest obs and near term guidance indicate patchy fog will form in the valleys of the Alleghenies. High pressure ridge will remain over the region Monday, accompanied by partly to mostly sunny skies and light wind. Mixing down model 900mb temps yields expected highs ranging from the mid and upper 30s over the northern mountains, to the mid and upper 40s in the Lower Susq Valley. && .SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/... Latest model guidance tracks a surface low through the Great Lakes into southern Ontario/Quebec Monday night into Tuesday, with the trailing cold front coming through Tuesday PM. Moderately strong WAA/moisture transport via southerly low level jet supports high confidence in precipitation late Mon night into Tuesday morning. An initial few-several hours period of snow still appears likely over the central mtns and northern tier of PA late Monday night/early Tuesday, as precip encounters the retreating dry and cold sector. This could lead to some minor travel impacts during the early AM commute over the northern mountains and will continue to message risk via HWO. The latest NBM/WPC blend supports less than an inch of accumulation along the I-80 corridor, but 1-3 inches over the mountains of northern Pa. 18Z model soundings indicate even the mountains north of KIPT are likely to change to rain by 12Z-15Z Tuesday. The rain should taper off from northwest to southeast Tuesday afternoon, as the trailing cold front crosses the region. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... An upper trough and pool of anomalously cold air is progged to swing through the northeast CONUS Wed-Thu. Surface ridging and associated low inversion heights indicate lake effect snow showers will be quite light, with only light accumulations possible across the Allegheny Plateau. By late week, large surface high is progged to overspread the region, ending the threat of lingering lake effect flurries and likely accompanied by abundant sunshine Friday-Saturday. Below normal temperatures should give way to milder conditions by next weekend, as the high passes off the coast and a return southwest flow develops. Several weak waves within the flow may provide for a few periods of snow showers, mainly across the northern mountains, late next week. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... 06Z TAFS sent. Most of the area clear now, with a slight west wind. Have a tempo group in at JST, as low clouds have been moving in and out of that area. Earlier discussion below. 00z update... Lower clouds (MVFR to fuel alternate restrictions) will be prevalent at KBFD and KJST for much of the overnight period into early Monday, owing to some low-level moisture and an upslope W-NW flow. Lower clouds are expected to have dissipated at these terminal sites by 12-15z, with VFR returning for the balance of the day. Elsewhere for the central PA terminal sites (KAOO, KUNV, KIPT, MDT, and KLNS), generally unrestricted conditions are foreseen through the day Monday. W-NW surface winds at 5-8 kt for much of tonight, will diminish to light and variable (3-5 kt or less) for most of Monday. SE winds at 5-8 kt are expected to develop late in the period (after 21-22z Monday). .Outlook... Mon night-Tue... Restrictions probable in lower ceilings and either rain or a wintry mix. KBFD and KIPT are the most likely terminal sites to see a period of snow late Mon night or early Tue. Wed-Fri...Mainly VFR anticipated. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/Lambert LONG TERM...Fitzgerald/Gartner AVIATION...Jurewicz/Lambert/Martin

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