Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 161144 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 644 AM EST TUE DEC 16 2014 .SYNOPSIS... SEASONAL TEMPERATURES WILL RETURN BEHIND A COLD FRONT WHICH WILL PASS THROUGH ON TUESDAY EVENING. SCATTERED MOUNTAIN SNOW SHOWERS ARE THEN EXPECTED FOR MID AND LATE WEEK. CONFIDENCE IS LOW CONCERNING ALL DETAILS AND POTENTIAL IMPACTS ASSOCIATED WITH A LOW PRESSURE SYSTEM EXPECTED TO TRACK NORTHEAST FROM THE GULF COAST STATES OFF THE EAST COAST THIS WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 630 AM UPDATE... FIRST VOLLEY OF SHOWERS HAS TOTALLY FIZZLED...BARELY RAINING AT ANY OF THE WRN TERMINALS. LLVL RH IS GETTING HIGH AND HIGH POPS ARE ON ORDER AS THE CLOUD TOPS IN WV ARE GETTING COLDER AND RADAR ECHOES MORE ORGANIZED OVER SWRN P AND WV. LTG NR KCVG...BUT SHOULD NOT BE A CONCERN TODAY WITH A STABLE LOWER ATMOSPHERE. COULD SEE A STRIKE OR TWO ALONG THE MD BORDER...BUT WILL NOT MENTION AT THIS POINT. QPF LOOKS TAME...LESS THAN A QUARTER OF AN INCH. PREV... UPPER LOW SPINNING OVER NRN IL WILL FILL SLIGHTLY AND SLIDE EASTWARD COVERING LWR MI BY EVENING. THE LARGER TROUGH WILL START TO ABSORB THIS FEATURE. COMPLICATED FRONTAL FEATURES TO OUR WEST WILL NOT SIMPLIFY MUCH AS THE SLIGHTLY DIFFERENT AIR MASS MOVES IN LATER TODAY. DESPITE +8C 8H TEMPS...WE ARE SEEING LITTLE BENEFIT FROM THESE UNUSUALLY MILD TEMPS HERE AT THE SFC DUE TO LUDICROUS INVERSION. LOW STRATUS STILL STUCK IN THE NE HALF OF THE AREA AND PATCHES IN THE SOUTH AS WELL. THIS SHOULD NOT CHANGE MUCH UNTIL LATE MORNING...WHEN SOME LARGER HOLES DUE TO SOME MIXING MAY APPEAR IN THE EAST. FOG IS NOT DENSE ANYWHERE AT 07Z...BUT THE WINDWARD SLOPES OF THE MTS MAY HAVE A LITTLE DRIZZLE. SUB FREEZING TEMPS IN THE S...BUT THIS IS ALSO WHERE THERE ARE NO/LESS LOWER CLOUDS TO MAKE SPRINKLES. THE FIRST ARM OF SHOWERS ASSOCIATED WITH THIS COMPLEX CIRCULATION/PATTERN WILL APPROACH THE AREA THIS MORNING...BUT LATEST GUIDANCE CONTINUES TO HOLD IT OFF A LITTLE LATER. THUS...WILL KEEP POPS LOW IN THE CENTRAL AND EAST FOR THE MORNING. NOT UNTIL 14-15Z WILL PRECIP BE CERTAIN OVER THE WESTERN MOUNTAINS. BUT ALL MODEL GUIDANCE MAKES NUMEROUS SHOWERS OR EVEN MORE-WIDESPREAD COVERAGE OVER MOST IF NOT ALL OF THE AREA BY 20Z. DRY SLOT MOVES IN FROM THE SOUTHWEST...BUT WESTERLY FLOW BEHIND THE OCCLUSION WILL KEEP LOTS OF CLOUD COVER AND SCT SHRA OVER THE WEST LATER IN THE AFTN. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... UPPER PATTERN WOBBLES ITSELF INTO A BROAD UPPER LOW WITH A FEW CLOSED CONTOURS OVER THE GREAT LAKES AND LOWER ONT/SRN QUE. MOISTURE PULLED AROUND THE SYSTM AND PULLED FROM THE GREAT LAKES WILL ASCEND THE WRN HIGHLANDS AND CREATE NUMEROUS SHOWERS FOR TONIGHT. LESS COVERAGE WILL BE HAD LATER TONIGHT AND WEDNESDAY MORNING...BUT SHOWERS WILL CONTINUE INTO WEDNESDAY AS THE UPPER LOW CENTER SLIDES EAST AND THE COLDER AIR FILTERS IN. THIS SHOULD TURN ANY SHOWERS OVER TO SNOW SHOWERS WED MORNING. DOWNSLOPE SHOULD KEEP IT PARTLY TO MOSTLY SUNNY IN THE SE. SOME VERY LIGHT ACCUMS COULD OCCUR ON THE WRN MTS. IT WILL GET KIND OF WINDY ON WED - ESP IN THE LAURELS WHERE GUSTS COULD GET INTO THE 30S. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A RATHER POTENT SHORTWAVE TROUGH WILL PIVOT EASTWARD FROM THE GREAT LAKES AND CROSS THE AREA WED NGT BEHIND THE DEPARTING SURFACE LOW LIFTING SLOWLY NORTH FROM MAINE INTO NEW BRUNSWICK CANADA. A REINFORCING SHOT OF COLD AIR ALOFT SHOULD ACCOMPANY THE TRAILING SHORTWAVE WHICH MAY ACT TO BRIEFLY ENHANCE POST FRONTAL LAKE EFFECT AND UPSLOPE SNOW SHOWERS OVER THE WESTERN HIGHLANDS. ITS NOT OUT OF THE QUESTION THAT THE STRONG VORTMAX COULD INDUCE SNOW SHOWERS EAST OF THE ALLEGHENY FRONT WED NGT HOWEVER THE GLOBAL MODEL QPFS ARE NOT IN FAVOR OF THIS OUTCOME. DESPITE A WELL ALIGNED WNW FLOW AND FAIRLY STRONG LOW LEVEL COLD AIR ADVECTION...MODEL SOUNDINGS SHOW RATHER SHALLOW MOISTURE/LOW INVERSION HGTS ALONG WITH DRY AIR WHICH SHOULD LIMIT MAX SNOW ACCUM POTENTIAL (POTENTIAL FOR THIS MUCH OR WORST CASE) OVER THE NW MTNS TO 2-3 INCHES BY THU MORNING...WITH AROUND 1 INCH ACCUM THE MOST LIKELY OUTCOME. OVERALL THE GENERAL WEATHER TREND IN CENTRAL PA WILL BE TOWARD A BRISK AND COLDER PATTERN WED THRU FRI. LARGE SCALE SUBSIDENCE ASSOCIATED WITH SURFACE HIGH EXTENDING FROM THE GREAT LAKES INTO EASTERN CANADA SHOULD BRING AN END TO NUISANCE SNOW SHOWER ACTIVITY BY FRI NGT. CONCERNING THE POTENTIAL WEEKEND STORM... THERE IS BROAD MODEL CONSENSUS IN A SURFACE LOW DEVELOPING OVER THE GULF COAST REGION AND TRACKING NORTHEAST OFF THE EAST COAST THIS WEEKEND. HOWEVER...THERE CONTINUES TO BE A WIDE RANGE OF POSSIBLE SOLUTIONS WITH ABOVE AVERAGE SPREAD IN THE LOW TRACK. IN ADDITION TO THE LARGE SPREAD...THERE HAVE BEEN RUN-TO-RUN [IN]CONSISTENCY ISSUES THAT CONTINUE TO PLAGUE THE MODEL FCSTS IN PARTICULAR TODAYS 15/12Z RUN OF THE DETERMINISTIC ECMWF WHICH HAS BACKED OFF ON ITS BULLISH WINTER STORM SCENARIO THAT IT HAS BEEN ADVERTISING FOR THE PREVIOUS 4 CYCLES. CURIOUSLY BOTH THE GEFS AND ECENS SEEM TO BE LEANING MORE IN FAVOR OF A LOW TRACK CLOSER TO THE COAST - WITH A MEAN POSITION WEST OF THEIR RESPSECTIVE DETERMINISTIC MODEL CORES. WITH THE STORM STILL 5-6 DAYS OUT THERE IS A LOT OF TIME FOR THE FORECAST TO CHANGE. CONFIDENCE IS LOW REGARDING ANY POTENTIAL DETAILS OR IMPACTS WITH THIS SYSTEM. HIGH PRESSURE SHOULD BUILD INTO THE AREA EARLY NEXT WEEK. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... COMPLEX FCST TODAY...GIVEN THAT SOME AREAS ARE CLEAR WITH FOG FORMING...OTHERS MAY STAY CLEAR...AND LOW CLDS STILL IN PLACE ACROSS PORTIONS OF THE AREA. OTHER CONCERN IS THE FORMATION OF ICE IN AREAS THAT ARE CLEAR...GIVEN LIGHT WINDS AND HIGH HUMIDITY LEVELS. MAIN AREA IS ACROSS THE SOUTH AND SE. SEVERAL BANDS OF SHOWERS TO THE WEST. EXPECT ALL AREAS TO SEE RAIN TODAY...AS LOW PRESSURE TRACKS ACROSS THE LOWER LAKES. SOUTHERN AREAS MAY SEE A WIND SHIFT TO THE S-SW. NOT REALLY SEEING ANY LARGE WINDOW FOR VFR CONDITIONS. EXPECT IMPROVING CONDITIONS ON WED...AS COLD FRONT MOVES OFF THE COAST. IT WILL BE A WINDY DAY. OUTLOOK... WED...LOW CIGS/SHSNRA LIKELY W MTNS...MAINLY AM. THU-FRI...NO SIG WX EXPECTED. SAT...SNOW/REDUCED VSBY POSS SOUTHERN PA. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO NEAR TERM...DANGELO SHORT TERM...DANGELO LONG TERM...STEINBUGL AVIATION...MARTIN

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