Area Forecast Discussion
Issued by NWS State College, PA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KCTP 200801 AFDCTP Area Forecast Discussion National Weather Service State College PA 301 AM EST Sat Jan 20 2018 .SYNOPSIS... A large area of high pressure centered over the Lower Mississippi Valley will maintain fair skies for the next few days. Temperatures will climb above normal over the upcoming days with mainly dry weather continuing. A cold front will move through the area later Monday night and early Tuesday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Minor changes made to the previous evening update - mainly in terms of hourly temps and wind. Variable amounts of cirrus clouds will drift southeast across the region overnight, with the greatest percentage over northern and western PA. Temps will be milder than normal by 6-10 degrees F in most places overnight thanks to a 10-15 kt SW wind across northern and western parts of the CWA...with gusts to around 20 kts. A few locations across the Lower- Mid Susq Valley could see temps dip to around normal (in the low 20s) as a result of mainly clear skies and a decoupled boundary layer with nearly calm air. Elsewhere, min temps early Saturday will range from the mid 20s across the north, to the upper 20s to around 30F over the southern half of the state. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
-- Changed Discussion --
After a mostly Sunny morning in most places, the operational NAM, GFS and RAP show a rather shallow layer of stratocu clouds adevcting ESE and into the western zones during the late morning/early afternoon hours, and later in the afternoon or evening across the Susq Valley. The latest ensemble MOS pops continue to show a small chance of some light rain...mixed with wet snow flakes...reaching my far NW counties around sunset Saturday. Otherwise more of the same is expected with a gradual increase in mid and high clouds throughout the day. Highs on Saturday will range from near 40F north to the lower 50s across the south. However, a brisk westerly wind (averaging in the mid to upper teens (KTS) with gusts as high as 30 KTS during the late morning and afternoon Western high terrain and 20-25 kts elsewhere) will make it feel notably cooler than the actual air temp - or in the upper 20s across the higher terrain of the north and west, and upper 30s in the SE.
-- End Changed Discussion --
&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Another January thaw will bring a period of relatively mild weather to Central PA into early next week. Temperatures are not expected to be as warm as the previous thaw late last week, but departures should reach +10 to 15 degrees above average for mid to late January. The progressive pattern should keep the cool down through the middle part of next week rather brief before temperatures moderate/trend warmer into next weekend. A surge of warm advection ahead of a strengthening Mississippi Valley/Great Lakes cyclone will impinge on a retreating thermal gradient between I-80 and I-90. Forecast soundings indicate moisture will be rather shallow initially with areas of light rain confined mainly to the western and northern parts of the area. Elsewhere expect low clouds to develop with pockets of drizzle/mist and fog. Examination of thermal/moisture profiles specifically sfc temps and maxTw aloft suggest some patchy freezing drizzle is possible over parts of north-central PA Sat night and Sun night. The other concern may be black ice as snow melts during the day and then freezes at night. The risk of ice jam flooding will continue over the weekend and into early next week. See the hydro section for more details. The most likely period for widespread rain is Monday night into early Tuesday along/ahead of south-southwesterly LLJ axis and cold/occluded front. A secondary low may form in the lee of the Appalachians and support a period of enhanced rainfall over the eastern 1/2 of PA Tuesday morning. At this time, the total rainfall forecast for early next week does not appear to be as heavy as Jan. 11-12. Winds look rather blustery from later Tuesday into Wednesday on the backside of the low pressure system and may approach advisory criteria. Snow showers are likely downwind of Lake Erie into Wed night. Dry wx with moderating temperatures Thu-Fri. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Widespread VFR will continue overnight and much of Saturday as high pressure maintains control of the local weather pattern. A MVFR stratocu/stratus deck may advect East into the Western zones during the afternoon, and late in the day or evening across the SE. Some very light snow or flurries could develop from this cloud deck later Sat afternoon and evening over favorable upslope areas of the Alleghenies (KBFD and KJST TAF sites), as the clouds will be 1000 feet or so thicker. This will be watched closely and likely included in TAF updates. Strong winds aloft will slowly weaken as the gradient shifts to the northeast, however LLWS will continue overnight into Saturday morning. Outlook... Sun...Mainly VFR. Mon...Reduced conditions with rain showers associated with an approaching cold front. Tue...MVFR/IFR with snow showers west and north. MVFR/VFR central and eastern terminals. Wed...MVFR with snow showers west and north. VFR central and eastern terminals.
-- End Changed Discussion --
&& .HYDROLOGY... Main concern is watching water levels rise on Susq downstream on Harrisburg. Marietta gage /MRTP1/ continues its slow rise as ice builds up downstream. Gage above action stage and there is some minor flood concerns in Wrightsville ongoing. The Flood Watch for this area has been extended through the weekend, set to expire Monday afternoon. With milder temperatures there is potential for ice movement, as well as slow ice deterioration/thinning with time. All areas near rivers and streams that have significant ice buildup should monitor water levels closely for the next several days. && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Monday afternoon for PAZ065-066. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte/Lambert SHORT TERM...La Corte/Lambert LONG TERM...Steinbugl AVIATION...La Corte/Ceru HYDROLOGY... is the U.S. government's official web portal to all federal, state and local government web resources and services.