Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 282343 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 643 PM EST SAT FEB 28 2015 .SYNOPSIS... HIGH PRESSURE OVER PENNSYLVANIA WILL PASS OFF THE NEW ENGLAND COAST THIS EVENING. LOW PRESSURE TRACKING UP THE OHIO VALLEY SUNDAY WILL CROSS PENNSYLVANIA SATURDAY NIGHT...BRINGING SNOW AND MIXED PRECIPITATION TO CENTRAL PA THROUGH EARLY MONDAY MORNING. A STRONGER AREA OF LOW PRESSURE WILL LIKELY TRACK WEST OF PENNSYLVANIA LATE TUESDAY AND EARLY WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... HIGH CLOUDS SHOULD THICKEN UP QUICKLY TONIGHT AS MOISTURE STREAM EWRD ON FAST/ZONAL FLOW. HIGH PRESSURE STILL ALLOWING TEMPS TO DROP DUE TO LIGHT WINDS. BUT...WITH THE MOISTURE THICKENING UP A LITTLE QUICKER THAN ANTICIPATED...IT MAY HOLD TEMPS UP A FEW DEGS AND THEY SHOULD PRACTICALLY HALT EARLY TONIGHT. EXPECT THAT THE FASTER ONSET WILLBRING THE FIRST WAVE OF WARM ADVECTION SNOW INTO THE NW BY 09Z AND ACROSS ABOUT THE NWRN 3/4S OF THE AREA BY 13Z. BUT IT SHOULD BE ONLY BRIEFLY HEAVY. MAIN CHANGES ARE TO SHORT TERM. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... 630 PM UPDATE... 18Z NAM GFS AND MOST SREF MEMBERS FROM 15Z NOW AGREE UPON A SCENARIO NOT UNLIKE/VERY SIMILAR TO LAST WEEKEND/S STORM WHERE THE PRECIP MAY BE A LOT LIGHTER IN THE CENTRAL MTNS AND HEAVIER IN THE SERN THIRD OF THE AREA...AS COLD AIR HANGS ON MUCH LONGER THRU THE TIME WHEN IT IS PRECIPPING. THE TEMPS DO NOT WARM ABOVE FREEZING IN THE SRN TIER UNTIL VERY CLOSE TO THE END OF THE ACCUM PRECIP. DRY SLOT SEEMS TO HIT THE SC MTNS IN THE EARLY AFTN AND THEN SLIDE EAST AND END PRECIP BY 00Z MON IN THE SERN COS. THEREFORE WILL DOWNPLAY THE ZR AND GO WITHMORE SNOW AND SLIGHTLY HIGHER QPF IN THE AFTN FOR THE SERN COS. THIS MAKES A BIG CHANGE /UPWARD/ IN THE SNOW NUMBERS FOR THE LOWER SUSQ AND A SLIGHT DOWN- TICK FOR MUCH OF THE OTHER PARTS OF THE REGION EXCEPT THE WRN MTNS. ALL ARE STILL IN ADVY- LEVEL NUMBERS...BUT MORE FROZEN PRECIP IS EXPECTED NOW. WILL NOT ADJUST THE FLAGS...BUT RE- WORD THE WSW SLIGHTLY. PREV... UPCOMING PRECIP WILL EXTEND BETWEEN A 12-24 HOUR EVENT... MEANING THAT 24 HOUR WATCH/WARNING CRITERIA MUST BE USED TO VERIFY AMOUNTS. HERE IN CENTRAL PA...THAT MEANS A MID POINT OF 8" MUST ACCUMULATE IN 24 HOURS FOR WARNING CRITERIA TO BE MET...AND THE OVERWHELMING CONSENSUS AFTER LOOKING AT MORNING DATA SUITE IS THAT WE WON`T SEE THAT EXCEPT FOR SPOT AMOUNTS ACROSS THE NORTHWEST OR WEST CENTRAL MOUNTAINS WHERE WATCHES WERE IN EFFECT. COLLAB WITH ALL SURROUNDING OFFICES HAS PROMPTED ADVISORY ISSUANCES FOR ALL OF MY COUNTIES. ACROSS THE NORTHWEST...A GENERAL 6 TO 8 INCHES IS EXPECTED...WHILE ELSEWHERE 2 TO 4 INCHES AND A COATING OF ICE WILL BE COMMON. FOR THE FAR SOUTH AND SOUTHEAST... A COATING TO LESS THAN TWO INCHES OF SNOW IS EXPECTED TO BE FOLLOWED BY ONE TO TWO TENTHS OF AN INCH OF FREEZING RAIN. LITTLE IN THE WAY OF WIND MEANS THIS SHOULD NOT BE A PARTICULARLY DAMAGING OR DISRUPTIVE EVENT (IN TERMS OF POWER, ETC). BLEND OF MORNING MDL OUTPUT BRINGS LIGHT SNOW INTO THE WEST CENTRAL MOUNTAINS BEFORE DAWN SUNDAY. FOR THE REST OF CENTRAL PA...LGT SNOW IS LIKELY TO ARRIVE BY LATE AM. AGREE WITH PREVIOUS THINKING THAT HEAVIEST PRECIP WILL LIKELY HOLD OFF UNTIL STRONGER FORCING ARRIVES WITH APPROACH OF N STREAM SHORTWAVE DIVING ACROSS THE GRT LKS SUNDAY PM. ASSOC LL JET AND SURGE OF WARMER AIR ALOFT WILL LKLY CHANGE LGT SNOW TO A WINTRY MIX ACROSS SOUTHERN PA LATE SUNDAY AND SUNDAY EVENING...WHILE MDL SOUNDINGS AND ENSEMBLE PTYPE PLUMES INDICATE ALL SNOW ACROSS AREAS NORTH OF I-80. THE TRANSITION TO FREEZING RAIN SHOULD TAKE PLACE FROM LATE AFTERNOON THROUGH LATE EVENING SUNDAY ACROSS THE SOUTHERN HALF OF MY CWA. PRECIP LOOKS TO TAPER OFF IN ALL AREAS DURING THE PRE DAWN HOURS MONDAY MORNING. && .LONG TERM /MONDAY THROUGH SATURDAY/... BLUSTERY AND COLDER CONDITIONS WILL MAKE A RETURN ON MONDAY AS SYSTEM NUMBER ONE SLIDES OFF TO OUR EAST. OTHER THAN THE USUAL POST FRONTAL SNOWS SHOWERS...FAVORING WESTERN HIGHER ELEVATIONS...CONDITIONS WILL BE IMPROVING OVERALL. HIGH PRESSURE WILL BE SHORTLIVED MONDAY NIGHT INTO TUESDAY WHEN THE NEXT IN THE SERIES OF STORM SYSTEMS IS SLATED TO ENTER THE LOCAL WEATHER SCENE. THIS ONE PROMISES MORE OF A MESSY OUTCOME AS IT SHOULD TRACK WELL TO OUR NW...MEANING WARM AIR EVENTUALLY INVADING THE REGION...WITH A SNOW TO SLEET/FREEZING RAIN AND EVEN RAIN SCENARIO. SNOW AMOUNTS DO NOT LOOK TO BE THE BIGGEST PART OF THE MIDWEEK STORM AS WE ARE PROGGED TO WARM ALOFT RATHER QUICKLY. WITH A DEEP SNOW PACK AND A LOT OF COLD AIR TO DISPLACE...WE WILL LIKELY SEE A PERIOD OF ICING BEFORE WARM AIR EVENTUALLY CHANGES EVERYTHING TO RAIN TUESDAY NIGHT INTO WEDNESDAY. RAIN SHOULD TAPER OFF TO SCATTERED SHOWERS WITH THE PASSAGE OF THE TRAILING COLD FRONT EARLY WEDNESDAY. EARLIER MODEL RUNS SUGGESTED LATER WEDNESDAY INTO THURSDAY THERE COULD BE A RETURN OF SNOW TO SRN PA ASSOCIATED WITH A FLAT SRN STREAM WAVE...BUT LATEST OPERATIONAL ECMWF/GFS NOW KEEP THE SURFACE WAVE SUPPRESSED MAINLY SOUTH OF THE REGION..HINTING THAT ONLY FAR SERN AREAS WILL BE AT RISK FOR A PERIOD OF OVER RUNNING SNOW. THE 06Z GEFS IS A LITTLE MORE GENEROUS WITH THE POPS SO IT`S NOT OUT OF THE QUESTION THAT SOMETHING WILL YET HAPPEN AS MODELS TRY AND RESOLVE SMALL SCALE FEATURES DROPPING OUT OF CENTRAL CANADA INTO THE EASTERN US LONG WAVE. TOO FAR OFF TO LEAN ONE WAY OR ANOTHER FOR A SOLUTION. BEHIND THE MID WEEK SYSTEM...ANOTHER PUSH OF ARCTIC AIR WILL BRING TEMPS AND POPS BACK WELL BELOW NORMAL FOR LATE THURSDAY INTO FRIDAY. THE ONLY GOOD THING SEEMS TO BE EACH ARCTIC SHOT IS A LITTLE LESS POTENT THAN THE LAST AS WE LEAVE THE RECORD COLD OF FEBRUARY BEHIND. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... SURFACE HIGH PRESSURE...WITH VFR CONDITIONS...WILL DRIFT SLOWLY EAST THROUGH TONIGHT...WITH MID CLOUDS INVADING FROM THE WEST BETWEEN 03Z AND 05Z. CONDITIONS WILL BEGIN TO DETERIORATE LATE TONIGHT INTO EARLY SUNDAY...09Z TO 12Z...AS A WAVE OF LOW PRESSURE SLIDES INTO PENNSYLVANIA. AN EXPANDING AREA OF SNOW WILL SPREAD IN FROM THE OHIO VALLEY STARTING AROUND 09Z. AT THE SAME TIME...CLOUDS WILL THICKEN AND LOWER WITH WIDESPREAD RESTRICTIONS DEVELOPING FROM WEST TO EAST. THE SNOW IS EXPECTED TO CHANGE TO A WINTRY MIX ACROSS SOUTHERN PENNSYLVANIA LATER SUNDAY. CONDITIONS SHOULD BEGIN TO IMPROVE ON MONDAY AND REMAIN GOOD INTO EARLY TUESDAY...BEFORE THE NEXT SYSTEM PUSHES ANOTHER ROUND OF PRECIP AND REDUCED FLYING CONDS INTO THE AREA. OUTLOOK... SUN...WIDESPREAD IFR WITH SNOW NORTH AND MIXED PRECIPITATION SOUTH. MON...CIG/VIS REDUCTIONS MAINLY AM...THEN IMPROVING CONDITIONS. TUE...VFR AM. MIXED PRECIP WITH CIG/VIS REDUCTIONS POSSIBLE LATE. WED...CIG/VIS REDUCTIONS CONTINUE IN WINTRY MIX/RAIN. THU...SLOWLY IMPROVING CONDITIONS...LINGERING MVFR NW AND SE. && .CLIMATE... THE COLDEST FEBRUARY ON RECORD IS STILL LOOKING LIKELY. MONTHLY MEAN TEMPERATURES THROUGH THE 27TH...IPT 18.2...MDT 20.9. THE CURRENT RECORD COLDEST FEBRUARY..IPT 19.3...MDT 21.4 BOTH SET IN 1934. SO FAR...THIS MONTH IS THE THIRD COLDEST EVER AT IPT...AND FOURTH COLDEST EVER AT MDT. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 7 AM EST MONDAY FOR PAZ006-012-018-019-024>028-033>037-041-042-045-046-049>053- 056>059-063>066. WINTER WEATHER ADVISORY FROM 4 AM SUNDAY TO 7 AM EST MONDAY FOR PAZ004-005-010-011-017. && $$ SYNOPSIS...DANGELO/DEVOIR NEAR TERM...DANGELO/DEVOIR SHORT TERM...DANGELO/DEVOIR LONG TERM...LA CORTE AVIATION...JUNG/DEVOIR CLIMATE...

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