Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 042004 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 304 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/... 2 PM UPDATE: AFTER INGESTING NEW 12Z DATA AND LATEST ENSEMBLES...IT IS BECOMING APPARENT THAT THE AXIS OF HEAVIEST PRECIP WILL TEND TO BE A BIT FURTHER SOUTH THAN PREVIOUSLY ANTICIPATED. WE HAVE TRIMMED BACK THE WARNING TO OUR SOUTHERN BORDER COUNTIES...AND LOWERED THE OVERALL NUMBERS MORE IN LINE LATEST QPF/WWD SNOWFALL GUIDANCE. STILL POSSIBLE THE WARNING CONFIGURATION IS A BIT TOO ROBUST AND MAY YET NEED FURTHER TRIMMING LATER THIS EVENING AS WE GATHER NEWER ENSEMBLES AND HRRR DATA. TEMPERATURES HAVE RECOVERED ABOVE FREEZING OVER ALL BUT THE FAR NORTH. TEMPS FOR MUCH OF TODAY WILL REMAIN STEADY OR SLOWLY RISE BEFORE COLDER AIR BEGINS WORKING IN LATER TODAY AND TONIGHT. COLDER AIR ARRIVING LATER TODAY AND THIS EVENING WILL BRING A CHANGE BACK TO SNOW. LATEST BUFKIT SOUNDINGS SHOW SNOW IN JOHNSTOWN BY 20-22Z...ALTOONA/STATE COLLEGE 22-00Z...AND NOT UNTIL 03-6Z IN THE HARRISBURG-YORK-LANCASTER AREAS. IT`S OVER THESE SOUTHEASTERN ZONES WHERE THE PROBLEM WILL BE AS MUCH OF THE PRECIP THAT IS EXPECTED WILL FALL AS RAIN BEFORE THE COLD AIR FINALLY ARRIVES. 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. SREF AND 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. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... LATEST GEFS/SREF SHOW PRECIP ENDING FROM NW TO SE AS THE DAY WEARS ON WITH MUCH OF THE DAY ENDING UP DRY OVER MY NORTHERN TIER...AND MAINLY DRY AFTER 18Z NORTH OF I-80. STILL YET ANOTHER VERY COLD DAY IS IN STORE WITH MAX TEMPS SOME 20-30 DEG BELOW NORMAL. && .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 /20Z WEDNESDAY THROUGH MONDAY/... 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 DRYER AIR BEGINS MOVING INTO THE REGION FROM THE WEST AND NORTH BRINGING IMPROVING CONDITIONS. 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... FLOOD WATCH UNTIL 7 PM EST THIS EVENING FOR PAZ017-024-025-033- 034. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY FOR PAZ017>019-024>028-049>053-058. WINTER STORM WARNING FROM 7 PM THIS EVENING TO 7 PM EST THURSDAY FOR PAZ033>036-056-057-059-063>066. && $$ SYNOPSIS...GRUMM/LA CORTE NEAR TERM...LA CORTE SHORT TERM...LA CORTE LONG TERM...GRUMM AVIATION...RXR

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