Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 182115 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 415 PM EST THU DEC 18 2014 .SYNOPSIS... NORTHWEST WINDS WILL KEEP FLURRIES AND SCATTERED LIGHT SNOW SHOWERS OVER THE NORTH AND WEST INTO FRIDAY MORNING. HIGH PRESSURE WILL SLIDE DOWN FROM THE UPPER GREAT LAKES AND PROVIDE A GENERALLY FAIR PERIOD FOR MOST OF THE WEEKEND. AN UNSETTLED PATTERN WILL SET UP IN THE FIRST PART OF THE NEW WEEK. A WEAK LOW PRESSURE AREA COULD BRING LIGHT RAIN OR SNOW TO THE AREA ON MONDAY. THEN A SIGNIFICANT AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP OVER THE MIDWEST AND UPPER GREAT LAKES. THIS WILL LIKELY PRODUCE RAIN FOR THE STATE ON WEDNESDAY...FOLLOWED BY STRONG WEST WINDS AND SCATTERED MOUNTAIN SNOW SHOWERS FOR CHRISTMAS DAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... SEASONABLY COLD NORTHWEST FLOW ACROSS THE EASTERN LAKES WILL REMAIN IN PLACE THROUGH FRIDAY WITH THE TYPICAL DOWNWIND STRATUS ACROSS MOST OF CENTRAL PA. CYCLONIC FLOW ALOFT ON THE BACKSIDE OF NEWFOUNDLAND UPPER CUTOFF/REX BLOCKING PATTERN WILL KEEP WEAK OR NEARLY NEUTRAL COLD ADVECTION OVER THE REGION. A SOUTHERN STREAM WAVE STREAKING EASTWARD FROM THE TENNESSEE RIVER VALLEY THU AFTN WILL PRODUCE AREAS OF VERY LIGHT SNOW ACROSS THE LAUREL HIGHLANDS INTO THE SOUTH CENTRAL MOUNTAINS THIS EVENING WITH LITTLE IF ANY ACCUMULATION EXPECTED. WEST FACING SLOPES OF THE WEST CENTRAL MOUNTAINS AND LAUREL HIGHLANDS MAY SEE A LOCALIZED COATING TO AN INCH OR TWO OF SNOW AS THE UPPER AND BOUNDARY LAYER FLOW ALIGN FOR A PERIOD LATE TONIGHT INTO FRI MORNING. OTHERWISE EXPECT WIDESPREAD STRATUS TO PERSIST ACROSS MOST OF CENTRAL PA. THE SOUTHEAST WILL LIKELY SEE SOME DISSIPATION BY FRIDAY MORNING. SURFACE HIGH CENTERED OVER THE NORTHERN GREAT LAKES AND EASTERN QUEBEC WILL KEEP NORTH/NORTHWEST BOUNDARY LAYER FLOW GOING THROUGH FRI MORNING...TRANSLATING TO SFC WINDS IN THE 7 TO 11 MPH RANGE. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... UPPER FORCING SLIDES EAST OF THE REGION EARLY FRIDAY MORNING... WITH EXPANSIVE SURFACE HIGH PRESSURE BUILDING OVER THE AREA IN THE AFTERNOON. THUS...THE AMOUNT/COVERAGE OF THE SNOW SHOWERS AND FLURRIES SHOULD DIMINISH COMPLETELY ON FRIDAY. MINS WILL STAY A LITTLE MILDER THAN CLIMO WITH CLOUDS AROUND. MAXES ON FRIDAY VERY SIMILAR TO TODAY...WITH 30S FOR THE MOUNTAINS AND NEAR 40 IN THE LOW LANDS WITH THE HELP OF SOME DOWNSLOPE WARMING. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... 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 /20Z THURSDAY 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 TONIGHT. LATEST MDL SOUNDINGS POINT TOWARD PREDOMINANTLY MVFR CIGS/VSBYS AT KBFD. ELSEWHERE...MDL SOUNDINGS SUPPORT CIGS ARND 1500FT AT KJST INTO THIS EVENING...WHILE DRYING/DOWNSLOPING FLOW YIELDS PROGRESSIVELY HIGHER CIGS FURTHER EAST. A TROUGH OF LOW PRESSURE WILL PUSH THRU THE REGION TONIGHT...PERHAPS PRODUCING A PERIOD OF STEADIER LGT SNOW AT KBFD AND KJST BTWN 00Z-06Z FRIDAY WITH VSBYS IN THE 1-2SM RANGE. OUTLOOK... FRI...EARLY AM -SHSN/REDUCED VSBYS POSS AT KJST. SAT-SUN...NO SIG WX EXPECTED. MON...LOW CIGS WITH LGT RAIN/SNOW POSSIBLE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...STEINBUGL AVIATION...DEVOIR

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