Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 011829 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 129 PM EST SUN MAR 1 2015 .SYNOPSIS... WEAK LOW PRESSURE AND A DISTURBANCE AT UPPER LEVELS OF THE ATMOSPHERE WILL TRACK NORTHEAST UP THE OHIO VALLEY AND CROSS PENNSYLVANIA TODAY. THIS PAIR OF WEATHER FEATURES WILL BRING PERIODS OF LIGHT TO BRIEFLY MODERATE SNOW...THEN SOME MIXED PRECIPITATION TO SOUTH-CENTRAL PA AND THE LOWER SUSQ VALLEY LATE TODAY AND TONIGHT. HIGH PRESSURE WILL BRING FAIR AND COLD CONDITIONS TO REGION MONDAY AND MONDAY NIGHT. A STRONGER AREA OF LOW PRESSURE WILL LIKELY TRACK WEST OF PENNSYLVANIA LATE TUESDAY AND EARLY WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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BRIGHT BANDING AND ELEVATED CCS SHOWING THE PRECIP TRANSITION ZONE WELL AS IT TRANSLATES NORTH OF THE MD BORDER INTO THE SOUTH CENTRAL MOUNTAINS AND FAR LOWER SUSQ RIVER VALLEY. 3" OF NEW SNOW O.G. NEAR GREENCASTLE FROM A TRUSTED WEATHER SPOTTER AND NOW FREEZING RAIN OCCURRING AT 27F. SLEET HAD BRIEFLY MIXED IN EARLIER ACROSS SOUTHERN YORK. A GENERAL 2-4" IS EXPECTED SOUTH OF INTERSTATE 80 AND EAST OF ROUTE 99...WITH THE ADDITIONAL CHANGEOVER TO ICE ACROSS SOUTHERN PORTIONS OF THE SOUTH CENTRAL MOUNTAINS AND LOWER SUSQ RIVER VALLEY ADDING ANOTHER .1 TO .15" OF ICE ON TOP IN THOSE AREAS. OVERALL SCENARIO PLAYING OUT WITH WITH PERIODS OF SNOW (OF VARYING INTENSITY) CONTINUING TO INCREASE IN AREAL COVERAGE THIS AFTERNOON FROM SOUTHWEST TO NORTHEAST. STRONG VERTICAL SHEAR EVIDENT ACROSS THE REGION WITH 150+ KT 250 MB JET SLICING ENE ACROSS THE NORTHERN OHIO VALLEY AND EASTERN GLAKS. BOUNDARY LAYER CONVERGENCE AND FORCING IS BEST ACROSS SOUTHERN PA THIS AFTERNOON AND EVENING...IN VICINITY OF 850 MB JET FEATURES...FIRST OF WHICH HAS SPAWNED A FEW HOURS OF MODERATE TO LOCALLY HEAVY PRECIP RATES FROM NORTHERN MARYLAND INTO MY SOUTHEAST COUNTIES. THIS IS PROGGED TO EXIT EASTWARD BY LATE AFTERNOON/EVENING BEFORE A MORE BROAD AREA OF BOUNDARY LAYER CONVERGENCE DEVELOPS AS THE UPPER TROF NEARS. 12Z RAP HANDLED THE ONGOING CHANGEOVER QUITE WELL FOR AREAS ALONG THE MD BORDER...AND EXPECT MDT TO BE CHANGING OVER IN THE NEXT HOUR OR TWO...STARTING WITH A MIXTURE OF SLEET AND THEN MAINLY LIGHT FREEZING RAIN AFTERWARD WITH AROUND 0.10 INCH QPF. WILL CONTINUE TO RIDE WITH A BLEND OF CURRENT AND UPCOMING HIGH RES GUIDANCE FOR ICE ACROSS OUR SRN ZONES...UNLESS WE SEE REASON TO SIGNIFICANTLY DEVIATE. WE WILL CONTINUE TO HOLD OFF ON ANY UPGRADES TO WINTER STORM/ICE STORM WARNINGS AT THIS TIME...AS AMOUNTS ARE EXPECTED TO REMAIN IN THE .1 TO .15" RANGE OVERALL...WITH SOME APPROACHING .20" ON TOP OF THE 2-4" OF SNOW ACCUM. ELSEWHERE...GOOD CONSISTENCY OF PAST SEVERAL MODEL/ENSEMBLE CYCLES CONTINUES THIS AFTERNOON WITH RESPECT TO PTYPE...WITH BULK OF THIS WINTRY EVENT FALLING AS SNOW TO THE NORTH OF THE RT22/322 CORRIDOR IN CENTRAL PENN. AMOUNTS AND DISTRIBUTION HAVE BEEN TRICKY GIVEN THE LACK OF FORCING FARTHER NORTH...BUT IN GENERAL IT APPEARS THAT 2-4" WILL BE COMMON FOR MOST...WHILE BETTER UPSLOPE AND MOISTURE TRANSPORT INTO THE WEST CENTRAL MOUNTAINS AND LAUREL HIGHLANDS PRODUCE MAX AMOUNTS THERE...GENERALLY UP TO 6" BUT WE COULD SEE SOME SPOT AMOUNTS COME IN HIGHER. TEMPS WILL WILL CONTINUE TO SLOWLY RISE TO A LATE DAY HIGH IN THE UPPER 20S ACROSS THE CENTRAL AND NORTHERN MTNS...AND LOWER TO MID 30S ACROSS THE LOWER SUSQ VALLEY AND LAUREL HIGHLANDS RESPECTIVELY. WINDS WILL BE SOUTH TO SW AT 5-8 KTS IN MOST PLACES THROUGH TODAY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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PRECIP LOOKS TO TAPER OFF IN ALL AREAS DURING THE LATE EVENING THROUGH VERY EARLY MORNING HOURS OF MONDAY. LOW TEMPS TONIGHT /UNDER PLENTY OF LINGERING AND MORE SHALLOW...WARMER LOWER CLOUDS/ WILL RANGE FROM NEAR 20 DEG IN THE NORTH TO 30F IN ACROSS THE SOUTH. 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 GRADUALLY IMPROVING OVERALL THROUGHOUT THE DAY.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGH PRESSURE AND ITS FAIR WEATHER AND LIGHT WIND 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 /18Z SUNDAY THROUGH FRIDAY/...
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EXPECT BEST RADAR RETURNS TO OCCUR ACROSS CENTRAL AND SOUTHERN PA THIS AFTERNOON AND EVENING IN THE BEST LOW LEVEL CONVERGENCE. MIX TRANSITION TO ICE ACROSS SOUTH CENTRAL MOUNTAINS AND LOWER SUSQ WILL LIFT NORTH OF KMDT MID TO LATE AFTERNOON AS WEAK LOW PRESSURE FROM THE OHIO VALLEY TRACKS EASTWARD INTO THE LAUREL HIGHLANDS AND SECONDARY WEAK LOW PRES FORMS NEAR THE DELMARVA COAST. ACROSS THE NRN MTNS OF PA VSBYS SHOULD AVERAGE NEARLY 1SM HIGHER IN THE LIGHT SNOW. GENERALLY IFR TO LIFR CONDITIONS IN SNOW EXPECTED TO CONTINUE ALL DAY AND INTO THIS EVENING. CIGS REMAIN ABOVE 1500FT AT 1530Z ACROSS MOST CENTRAL AND ERN PA AIRFIELDS...BUT HAVE DROPPED OFF TO BELOW 1KFT AGL ACROSS THE WRN MTNS...AND WILL CONTINUE TO GRADUALLY DROP IN ALL AREAS AS THE DAY WEARS ON. STILL THE THREAT OF SOME FZRA MIXING IN FOR THE SOUTHERN TIER COUNTIES LATER THIS AFT AND THIS EVENING. VSBYS WILL IMPROVE OVERNIGHT AS SNOW COMES TO AN END...BUT CIGS WILL REMAIN LOW KEEPING MAINLY IFR CONDITIONS GOING BEFORE LIFTING TO MVFR IN THE CENTRAL AND EAST LATE. CONDITIONS SHOULD CONTINUE TO SLOWLY 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... 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.
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&& .CLIMATE... THE BOOKS HAVE CLOSED AND WE NOW HAVE /AND MADE IT THROUGH/ THE COLDEST FEBRUARY ON RECORD. MONTHLY MEAN TEMPERATURES WERE...IPT 18.1...MDT 20.9. THE PREVIOUS RECORDS FOR THE COLDEST FEBRUARY...IPT 19.3...MDT 21.4 BOTH SET IN 1934. THIS FEBRUARY RANKED AS THE THIRD COLDEST CALENDAR MONTH EVER AT IPT...AND FOURTH COLDEST EVER AT MDT. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY UNTIL 2 AM EST MONDAY FOR PAZ019-027- 028-037-041-042-045-046-049>053-056>059-063>066. WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR PAZ004>006- 010>012-017-018-024-033. WINTER WEATHER ADVISORY UNTIL 11 PM EST THIS EVENING FOR PAZ025-026-034>036. && $$ SYNOPSIS...DEVOIR/LAMBERT NEAR TERM...DEVOIR/LAMBERT SHORT TERM...DEVOIR/LAMBERT LONG TERM...LA CORTE/LAMBERT AVIATION...DEVOIR/LAMBERT CLIMATE...

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