Area Forecast Discussion
Issued by NWS State College, PA

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822 FXUS61 KCTP 090619 AFDCTP Area Forecast Discussion National Weather Service State College PA 119 AM EST Mon Dec 9 2019 .SYNOPSIS... After a fair weather weekend, a more active and occasionally stormy pattern is expected during the second week of December. Temperatures are forecast to surge well-above normal today and Tuesday, followed by a sharply colder trend Wednesday into Thursday. The brief warm-up will be accompanied by periods of rain which may end as light snow late Tuesday night. A mid to late week drying trend will likely reverse by next weekend with another complex storm system on the horizon. && .NEAR TERM /THROUGH TODAY/... Watching the temperatures across the southeast, as radar returns are now just to the south over NE Maryland. So far, temperatures holding up and dewpoints are coming up. Not much on radar to the west, until gets well into the midwest. Earlier discussion below. Extensive, layered cloud cover was spread across the region this evening, and some lowering/thickening of the clouds will occur overnight in advance of a warm front. However, EFSs and High Res models indicate little if any rain for most of the CWA through around daybreak. Steady light to ocnly moderate rain overspreads the region Monday morning and continues during the afternoon as the 08/18Z GEFS shows an axis of anomalously high 850 mb moisture flux (Nearly plus 4 sigma) moving northeast across Pennsylvania along with a 45 to 55kt mean 925 to 850 mb SSWrly wind max. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... Evening shift has a band of snow of 1 to 2 inches in the fcst. While there could be a little more, temperatures are warm to start, then drier air could limit precipitation later on. Will continue to look over the situation. Earlier discussion below. Highest QPF shifts to mainly the western half where 36hr rain totals will be around an inch. As the aforementioned LLVL wind max feature departs toward the New England states Monday night, rainfall intensity will decrease and lingering low clouds and some patchy light rain/drizzle will occur. Breezy and unseasonably mild temps are expected within the warm sector and min temps will be 4-6 deg F above normal High Temps for the date (between 40 and 50F from NW to SE). Sfc Cold front pushes east across PA very late Monday night/Tuesday morning, before slowing as it reaches the Delmarva/VA coast. A secondary and moderately tight 850-700 mb thermal gradient and FGEN forcing will occur across the SE 1/3 to 1/2 of the CWA, as the thermally direct R.E. region of a strong 180kt jet approaches from the Mid Ohio Valley and accentuates UVVEL Monday night and Tuesday morning. Boundary layer temps slip to critical changeover levels for wet snow beginning in the early evening Tuesday across the Central Mtns and Mid Susq Valley, then across our SE zones around 03-05Z Wednesday. A second, post-frontal period of rain Tuesday afternoon/evening will likely change to a several to 6-8 hour period of light to moderate wet snow with 1-3 inches of accumulation looking increasingly likely SE of a KAOO to KSEG and KMPO line with the highest amounts occurring across the ridges just to the NW of the I-81/I-78 corridor where some travel impacts are possible for the morning commute to work and school Wednesday. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Main change so far was to adjust lake effect snow showers a little. Rising height fields will limit response in our area. Other issue the weather for next weekend. In some regards, models show a similar pattern to what we have today. Earlier discussion below. It will turn sharply colder midweek as arctic air blasts into the region. Temperatures will be on the decline over the NW Tuesday afternoon (non diurnal over the NW half) and drop quickly Tuesday night areawide. There will be some potential for residual water or slush to freeze up quickly by Wednesday. Highs are forecast to drop by 20-30 degrees between Tuesday and Thursday, with minimum wind chills in the single digits and teens Thursday morning. Strong 1040+mb high pressure moves NE across the region Thu/Fri followed by another system which could bring rain or mixed precipitation Friday into Saturday. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... Low pressure which will move over the Upper Great Lakes will draw deep moisture in from the south. Lowering cigs and rain are expected through the night and on Monday. Weak low moving up the coast is currently pushing some IFR clouds into the SE from the east. Latest model soundings and HREF and SREF probability charts support a fairly high confidence of IFR conditions developing between 12Z-15Z over most of the area. LNS and BFD are the most certain and will likely turn poor first. MDT may be just on the edge of the really low marine clouds, but best bet is to take them down to IFR just a little later than LNS. The one area of less certainty in IFR clouds is over the Laurel Highlands (JST and maybe AOO), where a southerly flow is usually unfavorable for low cigs. Strong southwest winds aloft, combined with much lighter surface winds, will set the stage for low level wind shear across much of central Pa late tonight and Monday. Just the very end of the period (03-06Z Tues) is the next possibility of some lifting of the low clouds and mainly dry for the SE, but the NW looks wet/IFR most of the next 30-36 hours. Cold front moves through NW to SE on Tuesday. .Outlook... Tue...AM low cigs/shra, mainly N Mtns. Evening and overnight light snow possible southeast PA. Wed...AM light snow possible southeast PA. Thu...No sig wx expected. Fri...Low cigs possible, especially late. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Martin NEAR TERM...Lambert/Martin/RXR SHORT TERM...DeVoir/Lambert/Martin/RXR LONG TERM...DeVoir/Martin/Steinbugl AVIATION...Dangelo/Fitzgerald

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