Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 050259 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 959 PM EST WED MAR 4 2015 .SYNOPSIS... A WAVE OF LOW PRESSURE WILL TRACK SOUTH OF PENNSYLVANIA THIS EVENING AND EARLY THURSDAY. HIGH PRESSURE WILL BUILD SOUTHEAST INTO THE STATE FRIDAY AND SATURDAY. A STRONG UPPER-LEVEL RIDGE WILL BUILD INTO THE REGION EARLY NEXT WEEK. THIS SHOULD PROVIDE GENERALLY FAIR WEATHER AND SEVERAL DAYS OF NEAR NORMAL TEMPERATURES AND RELATIVELY DRY WEATHER. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... WATER VAPOR/SATL DERIVED PWAT IMAGERY SHOWING AN ATMOSPHERIC RIVER OF ANOMALOUS PWATS EXTENDING FROM THE S PACIFIC OCEAN NEWRD INTO THE MISS VALLEY AND EVENTUALLY PA. THIS DEEP MOISTURE PLUME IS OVERRUNNING AN EXPANSIVE ARCTIC HIGH PRES TO THE NORTH...CREATING A BAND OF MIXED PRECIP FROM THE PLAINS INTO SOUTHERN PA. AS OF 02Z...PTYPE IS LGT RAIN ACROSS MOST OF SOUTHERN PA. HOWEVER...THE HIGHER TERRAIN FROM KFIG/KUNV SOUTH THRU KJST IS NOW REPORTING SNOW. AS WEAK WAVE OF LOW PRES PASSES SOUTH OF PA OVERNIGHT...PRECIP WILL EXPAND NORTH ACROSS THE STATE...WHILE COLDER AIR FILTERS IN ON NW FLOW. ALL LATEST MDL DATA POINTING TOWARD A GENERAL 2-4 INCH SNOWFALL ACROSS THE SOUTHERN COUNTIES OVERNIGHT...WITH PERHAPS A FEW AMTS NR 6 ALONG THE MD BORDER. 18Z MDL SOUNDINGS AND LATEST HRRR OUTPUT BOTH INDICATE THERMAL PROFILES WILL REMAIN TOO WARM FOR SNOW ACROSS THE LOWER SUSQ VALLEY UNTIL ARND 06Z. THUS...HAVE WILL LOWER AMTS THERE. TEMPERATURES AT 02Z RUNNING FROM THE U20S ACROSS THE NW MTNS...TO THE U30S IN THE SOUTHERN VALLEYS. HOWEVER...ARRIVAL OF PRECIP AND LOW LVL COLD ADVECTION WILL DROP READINGS TO THE TEENS AND 20S BY DAWN. A STRONG JET ENTRANCE REGION ALOFT WILL SLIDE BY JUST NORTH OF THE REGION TONIGHT AND THURSDAY...SUPPORTING AN AREA OF POTENT LOW-MID LEVEL FRONTOGENETIC FORCING. MODELS RESPOND BY BRINGING A FAIRLY PROLONGED PERIOD OF PRECIP TO MY FAR SOUTHERN ZONES. 21Z SREF AND 18Z GEFS THREAT PAGES STILL PAINT MY FAR SERN ZONES AS HAVING THE HIGHEST RISK FOR HEAVY SNOW THROUGH MID DAY THURSDAY...WITH A RATHER SHARP CUT OFF ON THE BACK SIDE UP INTO THE CENTRAL MOUNTAINS. HOWEVER...LEANING TOWARD THE MORE RECENT 00Z AND HRRR GUIDANCE...WHICH INDICATES SLIGHTLY LOWER AMTS THAN EARLIER EXPECTED. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... BLEND OF LATEST MDL DATA INDICATE SNOW WILL TAPER OFF BY LATE AM ACROSS THE CENTRAL COUNTIES...AND MAY LAST UNTIL LATE AFTN ACROSS YORK/LANCASTER COUNTIES. ARCTIC HIGH AND ASSOC DRY AIR MASS WILL ARRIVE EARLY OVR THE NW COUNTIES...RESULTING IN DRY/COLD WX THE ENTIRE DAY UP THERE. SOME PARTIAL CLEARING APPEARS LIKELY ACROSS THE NW COUNTIES LATE IN THE DAY. ELSEWHERE...MDL SOUNDINGS INDICATE A MID LVL CLOUD DECK WILL LINGER EVEN AFTER THE SNOW ENDS. OVERCAST SKIES AND COLD ADVECTION WILL LIKELY BLUNT ANY DIURNAL WARMING AND RESULT IN STEADY TEMPS THRU EARLY AFTN...THEN FALLING TEMPS LATE. CONSALL OUTPUT SUPPORTS DAYTIME TEMPS FROM ONLY ARND 10F ACROSS THE NW MTNS...TO THE L20S ACROSS THE SOUTHEAST COUNTIES...ANOTHER EXCEPTIONALLY COLD DAY FOR THE TIME OF YEAR. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... HIGH PRESSURE AND BELOW NORMAL LOW-LEVEL TEMPERATURES WILL DOMINATE THE REGION THURSDAY NIGHT INTO LATE FRIDAY. UNSEASONABLY COLD AIR...PERHAPS THE LAST OF THE SIGNIFICANT ARCTIC SURGES OF OUR ENDLESS WINTER. BASED ON THE LOW TEMPERATURES NEAR AND BELOW 0F AND THE WINDS...THE POTENTIAL EXISTS FOR SOME AREAS TO EXPERIENCE WIND CHILLS OVERNIGHT THURSDAY INTO FRIDAY WHICH MIGHT REQUIRE AN ADVISORY ACROSS THE NORTHERN TIER COUNTIES. SATURDAY THE TEMPERATURES AT 850 MB RETURN CLOSER TO NORMAL AND HIGH PRESSURE DRIFTS TO OUR SOUTH. PENNSYLVANIA SHOULD REMAIN NORTH OF THIS WEAK HIGH....CUTTING OFF ANY MOISTURE TO THE SOUTH...KEEPING THE REGION IN WEAK WESTERLY FLOW INTO MONDAY. THE PERIOD SHOULD BE RELATIVELY DRY WITH ANY FRONTAL PRECIPITATION SUPPRESSED TO OUR SOUTH AND ONLY WEAK NORTHERN STREAM WAVES TO OUR NORTH TO GENERATE ANY PRECIPITATION. SO...KEPT THE POPS LOW THROUGH THE PERIOD AND ANY LIGHT PRECIPITATION WOULD LIKELY BE SNOW AS 850 HPA TEMPS STAY BELOW 0C. BEST CHANCE OF ANY PRECIPITATION WOULD BE IN NORTHERN AREAS SHOULD ONE OF THE NORTHERN STREAM WAVES PROVE TO BE STRONGER THAN GUIDANCE IMPLIES. A RIDGE IS FORECAST TO BUILD OVER THE REGION TUESDAY INTO WEDNESDAY AND OUR LOWER TROPOSPHERE TEMPERATURES SHOULD GET AT LEAST SLIGHTLY....ABOVE NORMAL....BOTH TUESDAY INTO WEDNESDAY. THIS SHOULD PROVIDE AT LEAST 2 DAYS OF NEAR SEASONAL TEMPERATURES FOR A CHANGE. RELATIVELY WARM DAYS AND COLD NIGHTS...A GOOD SLOW WAY TO MELT SNOW WITHOUT FLOODING. THE NAEFSBC AND GEFSBC SUGGEST A FRONTAL PASSAGE THURSDAY WITH SLIGHTLY COLDER TEMPERATURES AS ANOTHER HIGH PRESSURE SYSTEM IS FORECAST TO MOVE OVER THE NORTHEASTERN UNITED STATES THURSDAY INTO SATURDAY NEXT WEEK. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... MOISTURE OVERRUNNING A WAVY COLD FRONT TO THE SOUTH OF THE AREA WILL BRING ANOTHER ROUND OF RAIN/SNOW MAINLY TO AREAS SOUTH OF I-80 TONIGHT INTO EARLY THURSDAY. WIDESPREAD MVFR/IFR WILL CONTINUE OVERNIGHT THROUGH AT LEAST MID DAY THURSDAY BEFORE DRIER AIR BEGINS MOVING INTO THE REGION FROM THE WEST AND NORTH BRINGING IMPROVING CONDITIONS. WORST CONDS ATTM OVER LOWER SUSQ VALLEY WHERE DENSE FOG IS CAUSING VLIFR VSBYS AT KLNS. THIS SHOULD PERSIST THROUGH AT LEAST MIDNIGHT UNTIL STRONGER NW WINDS HELP TO MIX UP THE AMS. OUTLOOK... THU...SLOWLY IMPROVING CONDITIONS...LINGERING MVFR NW AND SE. FRI-SAT...MAINLY VFR. SUN-MON...MVFR WITH CHC -SHSN MAINLY NORTH AND WEST. VFR SE. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 10 AM EST THURSDAY FOR PAZ017>019-049-051-053. WINTER WEATHER ADVISORY UNTIL 1 PM EST THURSDAY FOR PAZ024>028- 034-035-050-052-056>059-063. WINTER STORM WARNING UNTIL 4 PM EST THURSDAY FOR PAZ033-036- 064>066. && $$ SYNOPSIS...GRUMM/LA CORTE NEAR TERM...FITZGERALD SHORT TERM...FITZGERALD/LA CORTE LONG TERM...GRUMM AVIATION...GARTNER/RXR

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