Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 190641 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 141 AM EST FRI DEC 19 2014 .SYNOPSIS... HIGH PRESSURE OVER THE GREAT LAKES WILL SLIDE EAST INTO PENNSYLVANIA THIS WEEKEND. AN UNSETTLED PATTERN WILL SET UP IN THE FIRST PART OF THE NEW WEEK. A WEAK LOW PRESSURE AREA COULD AFFECT THE AREA MONDAY. THEN A MORE SIGNIFICANT STORM IS EXPECTED MOVE INTO THE REGION FOR CHRISTMAS EVE...FOLLOWED BY STRONG WINDS AND SCATTERED SNOW SHOWERS FOR CHRISTMAS DAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... MAIN FCST ISSUE THIS MORNING WILL BE THE LIKELIHOOD OF VERY LGT WINTRY PRECIP OVR THE W MTNS...THE RESULT OF OROGRAPHIC FORCING AND SHALLOW LYR OF MOISTURE. LATEST MDL DATA SHOWS A PLUME OF HIGHER LOW LVL MOISTURE IN ASSOC WITH SFC TROUGH ALONG THE PA/NY BORDER. SFC OBS INDICATE PTYPES OF BOTH -SHSN AND -FZDZ IN THE REGION AND MDL SOUNDINGS INDICATE BORDERLINE TEMPS AT CLOUD TOP OF ARND -10C...SO WILL CONTINUE TO FCST SCT -SHSN AND PATCHY -FZDZ OVR THE W MTNS THIS AM. ADVISORY WAS COLLABORATED WITH ADJ OFFICES OVR THE N MTNS...WHERE MDLS INDICATE A GREATER LIKELIHOOD OF MEASURABLE FZDZ. HOWEVER...SOME FZDZ IS ALSO POSSIBLE FURTHER SOUTH OVR THE LAUREL HIGHLANDS. ELSEWHERE...WEAK CAA AND PERSISTENT STRATO CU SHOULD TRANSLATE TO SLOWLY FALLING TEMPS EARLY THIS AM WITH LOWS IN THE 20S OVER MUCH OF CENTRAL PA AND THE L30S IN THE SUSQ VALLEY. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... SFC TROUGH AND RIBBON OF HIGHER LOW LVL MOISTURE WILL SLIDE SOUTH ACROSS THE REGION LATER TODAY. OROGRAPHIC LIFTING OF THIS SHALLOW MOIST LYR MAY CONTINUE TO PRODUCE A BIT OF -SHSN/-FZDZ ACROSS THE LAUREL HIGHLANDS THRU EARLY AFTN. OTHERWISE...ARRIVAL OF DRIER AIR IN WAKE OF TROF SHOULD PRODUCE PARTIAL CLEARING...ESP WHERE WEST WIND DOWNSLOPES THE MTNS ACROSS THE SUSQ VALLEY. MAX TEMPS SHOULD BE SIMILAR TO THURSDAY...WITH U20S OVR THE HIGHEST TERRAIN OF THE ALLEGHENIES...TO THE U30S ACROSS THE LOWER SUSQ VALLEY. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... HIGH PRESSURE WILL SHIFT SLOWLY EASTWARD FROM THE GREAT LAKES INTO NORTHERN NEW ENGLAND BY 12Z MONDAY. RESIDUAL LOW LEVEL MOISTURE ALONG WITH NRN STREAM SHORTWAVE ENERGY ATTEMPTING TO UNDERCUT AN UPPER RIDGE/HIGH HEIGHTS MIGRATING OVER SOUTHEASTERN CANADA SHOULD LIMIT SUN INTERVALS---HOWEVER THE SUN SHOULD AT LEAST MAKE A BRIEF APPEARANCE THIS WEEKEND. SPLIT FLOW REGIME ACROSS THE LOWER 48 WILL TRANSITION TO A HIGHLY AMPLIFIED PATTERN BY EARLY NEXT WEEK ACROSS THE LOWER 48...WITH A DEEP NEGATIVELY TILTED TROUGH EVOLVING OVER THE EASTERN 1/3RD OF THE CONUS. THE MODELS SEEM TO BE FORMING A CONSENSUS ON THE PESKY LOW THAT REFUSES TO BE WELL FORECAST...LIFTING IT SLOWLY FROM FL PANHANDLE NNEWD JUST OFF THE EAST COAST SUN-MON ALONG A LOW LEVEL BAROCLINIC ZONE THAT MAY NOT BUDGE PAST THE GULF STREAM AS THE FLOW ALOFT TURNS SOUTHWESTERLY/PARALLEL TO THE COASTAL FRONT. INCREASED POPS FOR MONDAY OVER THE SE BASED ON MULTI-MODEL/WPC BLEND. COMPLEX SFC PATTERN WITH SOME HINTS AT LOW LEVEL CAD ALONG WITH WAA ALOFT VIA SLY FLOW COULD MAKE FOR A MESSY MIXED PTYPE TRANSITION. AN INTENSE TRIPLE POINT SYSTEM DEVELOPING ON DEC 23-24 WILL LIKELY STEAL THE HEADLINES GIVEN ITS TIMING AND LARGE PORTION OF REAL ESTATE THAT WILL BE AFFECTED. WHILE THE DETAILS REMAIN UNCLEAR AT THIS POINT...TEMPERATURES SHOULD BE WARM ENOUGH TO SUPPORT RAIN ON THE FRONT SIDE OF THE SYSTEM BEFORE BRISK WNW WINDS DRIVE STRONG CAA EAST OF THE APPALACHIANS. THE TIMING OF THE COLD/OCCLUDED FRONT WILL BE KEY FOR PRECIPITATION TRANSITION FROM RAIN TO SNOW SHOWERS. AS THE SYSTEM SPINS UP INTO EASTERN CANADA...THE STRONG CAA CIRCULATING THROUGH THE GREAT LAKES AND OH VLY SHOULD LEAD TO LAKE EFFECT/UPSLOPE/WRAP AROUND SNOW SHOWERS OVER THE WESTERN ALLEGHENIES BY CHRISTMAS DAY. A PERIOD OF STRONG GUSTY WINDS ARE HIGHLY PROBABLE AS THE DYNAMIC SYSTEM INTENSIFIES SHIFTING NWWD FROM NEW ENGLAND INTO ONTARIO/QUEBEC. THE TAKE HOME MESSAGE IS THAT A VOLATILE PERIOD OF WEATHER WILL IMPACT THE AREA THROUGH CHRISTMAS DAY WITH POTENTIAL WIND...RAIN AND SNOW IMPACTS ALL ON THE TABLE. STAY TUNED. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... LOW LVL MOISTURE TRAPPED BENEATH INVERSION AND NORTHWEST FLOW OVER THE EASTERN GLAKS WILL KEEP STRATO CU IN PLACE ACROSS MOST OF CENTRAL PA THROUGH THE OVERNIGHT. LATEST MDL SOUNDINGS POINT TOWARD PREDOMINANTLY IFR CIGS/VSBYS AT KBFD AND KJST. THE MODELS SHOW SOME VARIATION BUT MVFR CIGS AT ALL OTHER TAF SITES EITHER ARE CURRENTLY OCCURRING OR WILL OCCUR BETWEEN 06Z TO 12Z. A TROUGH OF LOW PRESSURE WILL PUSH THRU THE REGION OVERNIGHT... PERHAPS PRODUCING A PERIOD OF STEADIER LGT SNOW AT KBFD AND KJST BTWN 06Z-12Z FRIDAY WITH VSBYS IN THE 2 TO 4SM RANGE. SKIES WILL STEADILY IMPROVE AS THE DAY CONTINUES WITH VFR CIGS BY 15Z AT ALL TAF SITES. EXPECT REDUCING CONDITIONS FRI EVENING AT ONLY BFD AND POSSIBLY JST. OUTLOOK... FRI...EARLY AM -SHSN/REDUCED VSBYS POSS AT KJST. SAT-SUN...NO SIG WX EXPECTED. MON...LOW CIGS WITH LGT RAIN/SNOW POSSIBLE. TUE...LOW CIGS WITH RAIN LIKELY. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR PAZ004>006-010-011-037. && $$ SYNOPSIS...LA CORTE NEAR TERM...FITZGERALD SHORT TERM...DEVOIR/FITZGERALD LONG TERM...STEINBUGL AVIATION...CERU/RXR

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