Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 141959 AFDCTP Area Forecast Discussion National Weather Service State College PA 259 PM EST Thu Dec 14 2017 .SYNOPSIS... A weak ridge of high pressure will slide across the region late today and tonight with cold, but mainly dry conditions. Another clipper will move north of the region overnight Friday and Saturday morning followed by high pressure and a brief moderating trend in the temperature Sunday. A series of cold fronts will move across the area late Sunday into Wednesday. Windy and colder temperatures will follow. && .NEAR TERM /THROUGH TONIGHT/... Welcome back GOES 16! The high res meso loop shows the strato-cu bands streaking over the newly fallen snow. The clouds are thickest over the Laurels where a flurry may still fall out of the sky. A chilly night is in store. With lighter winds and a snow cover, central and northern areas will drop into the single digits and low teens. Some weak Lake Effect snow showers should affect our northwesternmost counties as the high slips past to our east. && .SHORT TERM /FRIDAY/... After a cold start temperatures will recover only to highs near 20 in the north to around freezing in the extreme southeast. Clouds and snow showers will be most likely over the northern mountains as a shortwave turns the flow more NWLY and brings a chance of Lake Effect back into the areas normally affected this time of year. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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The period starts out with below normal 500 hPa heights and below normal 850 hPa temperatures. The heights and temperatures rise to above normal values over the northeastern United States Sunday as a strong ridge retrogrades to our south. The really warm air should stay to our southeast. The heights and temperatures settle back toward normal Tuesday and Wednesday at 500 hPa and 850 hPa respectively. Temperatures may rebound Thursday ahead of another frontal system. Overall with the strong ridge to our southeast the fronts do not get too far south. Saturday we should still be in the cold air with some LES based snow activity in the northwest. As the high retreats to our east temperatures should begin to rebound and the snow showers in the northwest diminish. Sunday into Monday a strong shortwave to our north will help bring in warmer air. We may be cold air dammed near the surface so the +1 to -2C air at 850 hPa may not translate to a warm boundary layer. The warm advection should bring snow and snow to rain in the south but QPF amounts are low and EFS based POPS are not very high in central and southern areas. As this northern stream wave zips by to our north it should drag cold air back into the region Tuesday into Wednesday. The northwest flow triggers snow in relatively high POPS in NW PA due to LES. This cold surge should be relatively fleeting and high pressure and a potential surge of warmer air in the NAEFS/GEFS. This suggests relatively warmer on Thursday. The Warm advection and approaching cold front will likely produce increased potential for snow in NW Thursday into Friday. Farther south any precipitation would likely be mixed or rain. A strong frontal boundary will likely push another surge of cold air into the region Friday into Saturday. At this time and recent GEFS/CMCE and combined NAEFS runs keep the strong ridge suppressed to our south. This keeps the warm air from getting here. This keeps us relatively dry with all the significant QPF events suppressed to our south. There is considerable spread in the ensemble members. And we have seen run-to-run variations in the solutions with the strong southwest Atlantic ridge. The NAEFS deeps reforming vortex over east-central Canada and maintains the sharp ridge over northwestern North America. This seems to keep us in or on the edge of cold air intrusions. Thus so far single model runs of big warm ups appear to disappear in the ensembles.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/... * Cloud/Ceiling info will be missing at KBFD until new part can be installed * Most of the region has VFR conditions. There are some lingering isolated light snow showers in the southwest mountains where MVFR ceilings are hanging toughest. Overnight will be clear to partly cloudy and cold with some MVFR ceilings expected to move back into the higher elevation terminals of the west and north. The chance of snow showers will be on the increase Friday, mainly over the north. Outlook... Sat...Scattered snow showers and local restrictions NW/Laurels. Sun-Mon...Mainly VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Grumm/La Corte SHORT TERM...Grumm/La Corte LONG TERM...Grumm AVIATION...Grumm/La Corte

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