Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 010614 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 114 AM EST SUN MAR 1 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 /UNTIL 8 AM THIS MORNING/... 930 PM UPDATE... HAVE MOVE START TIME OF THE WINTER WX ADVY UP/CLOSER BY A FEW HOURS TO ALLOW FOR FAST ONSET TIME TO THE SNOW. HAVE ALSO TRIED TO TWEAK WORDING IN STATEMENT TO KEEP MENTIONS OF ZR ALONG AND SOUTH OF ROUTE 22. HOWEVER...STILL THINK THAT MOST OF THIS WILL FALL AS SNOW. TEMPS RIGHT ON TRACK AND SHOULD BE NICE AND COLD AS THE SNOW STARTS OVERNIGHT. TEMPS WILL RISE AS THE CLOUDS MOVE IN...BUT SFC DEWPOINTS VERY LOW/DRY. PREV... 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 WILL BRING 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 /8 AM THIS MORNING THROUGH 6 PM MONDAY/... 930 PM UPDATE... STILL THINKING THAT MOST PRECIP - EVEN ALONG THE MD BORDER - WILL BE SNOW...AS TEMPS REMAIN COLD THROUGH THE TIME OF HEAVIEST PRECIP. THE VERY WEAK LOW DEVELOPING ON THE DELMARVA AND RUSHING OFF SHORE LATER SUNDAY WILL ENHANCE THE PRECIP/SNOW OVER THE SERN COS...AND HAVE TRIED TO REFLECT THIS IN THE UPDATE. DID NOT WANT TO GO TOO WILD WITH CHANGES BUT THE 18Z RUNS AND NEWEST 00Z NAM PORTRAY A DECENT SLUG OF COLD/FROZEN PRECIP ROLLING THRU THE FAR SERN COS IN THE AFTERNOON AND EARLY EVENING. ONLY AT THE TAIL END OF THAT PRECIP - AS THE DRY SLOT OCCURS - IS THERE ENOUGH WARMING ALOFT TO CHANGE THE P-TYPE TO LIQUID OR SLEET. VERY INTERESTING PART OF THE FORECAST WILL BE THE SNOW TYPE. THERE IS A REALLY GOOD SIGNAL IN THE UPPER PART OF THE CLOUDS IN THE MIDDLE OF THE DAY WHERE THE BEST VERTICAL MOTION IS SQUARELY IN THE PREFERRED DENDRITIC GROWTH ZONE AROUND -15C. THEN...IT FALLS THROUGH A HIGHLY MOIST/SATURATED COLUMN AND GETS ONLY CLOSE TO MELTING INMOST PLACE. THIS COULD MAKE SOME GIANT BUT WET FLAKES. THUS...A HIGH WATER CONTENT AND HEAVIER SNOW. THE SNOW PHYSICS...THE WINDS ALOFT AND SFC TEMPS ALL WILL PULL THE SNOW ACCUMS ONE WAY AND ANOTHER. HOWEVER...TEMP PROFILES LOOK PRETTY SIMILAR TO PAST WEEKENDS VERY SIMILAR STORM. MANY SIMILARITIES EXIST WITH THAT PREV STORM...BUT THE TEMPS APPEAR JUST SLIGHTLY COLDER. THINKING THAT WE WILL GET BIGGER FLAKES BUT END UP WITH THE SAME WATER CONTENT AND SLIGHTLY HIGHER SNOW ACCUMS OVER MOST OF THE AREA. BUST POTENTIAL EXISTS IN THE SE...WHERE IF THERE ENDS UP BEING NO TURNOVER TO MIX/ZR WILL MEAN THAT THE 0.6 INCHES OF WATER PROGGED THERE MAY NUDGE THEM NEAR WARNING AMOUNTS. EVEN THIS SEEMS VERY SIMILAR TO THE 21ST. 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 WITH MORE 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 NIGHT 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 SHORT LIVED 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 /06Z SUNDAY THROUGH THURSDAY/... VFR CONDITIONS ACROSS CENTRAL PA AT 06Z AS HIGH PRESSURE WHICH HAS PROVIDED VFR CONDITIONS ACROSS THE REGION DRIFTS EASTWARD. AS A WAVE OF LOW PRESSURE AND ASSOCIATED SNOW RAPIDLY APPROACH FROM THE WEST...EXPECT A CORRESPONDING RAPID DETERIORATION OF CONDITIONS FOR MOST OF THE REGION...BETWEEN 08Z AND 12Z. EXPECT FAR SOUTHEAST AIRFIELDS TO HOLD ON TO VFR CONDITIONS LONGEST...AND MAY MAKE IT THROUGH MID/LATE MORNING BEFORE THE SNOW AND RESTRICTIONS MOVE IN. GENERALLY IFR TO LIFR CONDITIONS IN SNOW EXPECTED ALL DAY SUNDAY AND SUNDAY NIGHT. STILL THE THREAT OF SOME FZRA MIXING IN IN THE SOUTHERN TIER COUNTIES LATER SUNDAY AND SUNDAY NIGHT. CONDITIONS SHOULD SLOWLY BEGIN TO IMPROVE ON MONDAY...BUT EXPECT RESTRICTIONS TO LINGER IN THE WESTERN AND NORTHERN HIGHER TERRAIN ON COLD NORTHWEST WINDS AND TYPICAL OROGRAPHIC SNOW SHOWERS. BRIEF RESPITE LATER MONDAY INTO EARLY TUESDAY...BEFORE THE NEXT SYSTEM PUSHES ANOTHER ROUND OF PRECIPITATION AND REDUCED FLYING CONDITIONS INTO THE AREA LATER TUESDAY AND WEDNESDAY. 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 ALMOST IN THE BOOKS. 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 5 AM EARLY THIS MORNING TO 2 AM EST MONDAY FOR PAZ019-027-028-037-041-042-045-046-049>053-058. WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR PAZ004>006- 010>012-017-018-024-033. WINTER WEATHER ADVISORY FROM 5 AM EARLY THIS MORNING TO 11 PM EST THIS EVENING FOR PAZ025-026-034>036. WINTER WEATHER ADVISORY FROM 8 AM THIS MORNING TO 2 AM EST MONDAY FOR PAZ056-057-059-063>066. && $$ SYNOPSIS...DANGELO NEAR TERM...DANGELO SHORT TERM...DANGELO LONG TERM...LA CORTE AVIATION...JUNG/RXR CLIMATE...

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