Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 260728 AAD
AFDCTP

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE STATE COLLEGE PA
228 AM EST WED NOV 26 2014

.SYNOPSIS...
LOW PRESSURE FORMING OFF THE SOUTHEAST COAST WILL DEEPEN
SIGNIFICANTLY AS IT MOVES NORTHEASTWARD ALONG THE EAST COAST ON
WEDNESDAY...BRINGING SIGNIFICANT SNOW TO MUCH OF CENTRAL
PENNSYLVANIA. ANOTHER SHOT OF COLDER AIR WILL FOLLOW FOR THE END
OF THE WEEK...BEFORE TEMPERATURES MODERATE OVER THE WEEKEND AND
INTO EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
MESO ANAL AT MIDNIGHT SHOWS THE LOW FORMING JUST OFF THE GA COAST.
MODELS AGREE IN TRACKING THE STORM UP ALONG THEN OFF THE NJ COAST
BY 100 MILES OR SO. THIS SHOULD ASSURE A WIDESPREAD MODERATE TO
HEAVY SNOW OVER MUCH OF EASTERN PA WITH SIG ACCUMS ALL THE WAY
BACK INTO CENTRAL AREAS.

HAVE MADE NO CHANGES TO THE UPDATE PACKAGE. INITIAL THOUGHTS FOR
THE NEXT UPDATE ARE THAT WE WILL BE HARD PRESSED TO REACH WARNING
SNOW AMOUNTS OVER OUR VERY SERN COUNTIES WHERE A RAIN-SNOW MIX
COULD LAST A WHILE. HOWEVER I WILL NOT CHANGE THE WARNING
CONFIGURATION DUE TO EXPECTED IMPACT ON THE HEAVY HOLIDAY TRAVEL.

FROM EARLIER...

LITTLE CHANGE TO THE GOING FORECAST THIS EVENING. HIGH PRESSURE
CENTERED ALONG THE IL/IN BORDER BUILDING EASTWARD THROUGH THE OHIO
VALLEY WITH RIDGE AXIS EXTENDING NEWD ALONG THE LAKE ERIE
SHORELINE TO LAKE ONTARIO. STRATUS IS PACKED AGAINST THE
ALLEGHENIES OVER NORTHWEST PA. MID AND HIGH CLOUDS HAVE OVERTAKEN
THE REMAINDER OF CENTRAL PA THIS EVENING...AND WILL BE THICKENING
AS THE NIGHT WEARS ON. TEMPERATURES HAVE FALLEN TO THE LOWER 30S
IN MOST PLACES AND WILL DROP A FEW MORE DEGREES ACROSS THE NORTH.

STAGE IS SET FOR A LIGHT TO MODERATE SNOWFALL ACROSS A GOOD PART
OF CENTRAL AND EAST CENTRAL PA. MINOR ADJUSTMENTS TO SNOWFALL MAP
THIS EVENING FOR QUICKER EXIT OF SNOWFALL WEDNESDAY AFTERNOON...
AND SLIGHTLY LESSER QPF ALONG THE WESTERN EDGE OF THE WARNINGS.
HRW-ARW SUGGESTS ACCUMULATING SNOWFALL IS OVER BY 21Z...EVEN
ACROSS THE EAST...AND IS THE MOST AGGRESSIVE IN PUSHING THE
ACCUMULATING SNOWFALL OUT OF MY CWA WED AFTERNOON. HAVE NUDGED
THINGS IN THAT DIRECTION...AS OTHER GUIDANCE IS ALSO FASTER...BUT
MAINTAINED A BLEND OF GUIDANCE MID TO LATE AFTERNOON.

FOR THE OVERNIGHT...PRECIP OVERSPREADING THE SOUTHERN TIER
COUNTIES QUICKLY AFTER 08Z...WITH QPF APPROACHING A TENTH OF AN
INCH BY 12Z. TEMPS ALOFT AND ON THE SURFACE SUGGEST THAT PRECIP
STARTING OVER SOUTHERN /ESPECIALLY SE/ AREAS LATE TONIGHT WILL
LIKELY BE AT LEAST A MIX OF RAIN AND SNOW WITH LIGHT SNOW ON THE
NORTHERN EDGE. SIMPLY...PRECIP WILL MOVE INTO SOUTHERN HALF OF CWA
BEFORE SUNRISE AND WILL BE LIGHT...BUT QUICKLY INTENSIFY DURING
THE MORNING RUSH HOUR ACROSS THE SOUTH.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
WINTER STORM WARNINGS/ADVISORIES NOW IN EFFECT.

A LOW PRESSURE SYSTEM DEVELOPS AND INTENSIFIES AS IT TRACKS FROM
THE CAROLINA COAST AT 12Z WED TO OFF THE NJ COAST BY 00Z THU...
BRINGING BIGGEST IMPACTS TO CENTRAL PA DURING THE DAY WED.

CONFIDENCE IS GROWING IN THE STORM TRACK WITH GFS COMING IN LINE
WITH THE ECMWF CLOSER TO THE COAST...WHICH WILL PUSH THE QPF
SHIELD A BIT FURTHER WEST. PRECIP WILL BE ONGOING IN THE SOUTH BY
SUNRISE...AND SPREADING QUICKLY INTO THE CENTRAL AND NORTHEAST BY
MID MORNING. ANY RAIN WILL QUICKLY CHANGE TO SNOW IN THE SE AS
COLUMN COOLS. PERIOD OF HEAVIEST INTENSITY PRECIP WILL BE WED
MORNING THROUGH MID AFTERNOON...WHERE SNOW RATES COULD BE 1-2
INCHES PER HOUR IN THE WARNING AREA. LATEST WWD GRAPHICS CONTINUE
TO SHOW A SWATH OF 6-8 SNOWS OVER THE SERN 1/3 OR SO OF MY FCST
AREA. CONFIDENCE FOR SIG SNOWS UP INTO CENTRAL/NW PA NOT AS HIGH
GIVEN THE LACK OF A SIG EASTERLY LOW LEVEL WIND ANOMALY IN THE
ENSEMBLES...AND A SHORTWAVE SLIDING IN FROM THE WEST WHICH MAY
SHARPEN GRADIENT OF SNOW. BUT FOR A COUPLE INCHES OF SNOW AND
IMPACTS ON THE BUSIEST TRAVEL DAY OF THE YEAR WE STRUNG AN
ADVISORY OVER THE NORTHERN EDGE OF THE WARNING AREA.

SNOW SHOULD TAPER OFF QUICKLY BY LATE WED AFT/WED EVE AS STORM
QUICKLY MOVES INTO NEW ENGLAND. FLOW TRANSITIONS BACK TO A NW FETCH
ACROSS THE LAKES...WITH LIGHT SCT SNOW SHOWERS POSS BY THU MORNING
IN THE UPSLOPE OF THE WESTERN HIGHER TERRAIN.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
UPPER TROFFING OVER THE EASTERN THIRD OF THE COUNTRY AT THE START
OF THE LONG TERM PERIOD IS FORECAST TO FLATTEN OUT INTO AN
EXTENSIVE WEST TO EAST ZONAL FLOW PATTERN COVERING MUCH OF NORTH
AMERICA. HEIGHTS OVER THE NORTHEASTERN U.S. ARE THEN FORECAST TO
RISE FROM LATE IN THE WEEKEND ONWARD AS THE CABOOSE IN THE CURRENT SHORTWAVE
TRAIN EXITS THE EAST COAST ON FRIDAY AND ENERGY APPROACHING THE
PACIFIC COAST CLOSES OFF AND BUILDS HEIGHTS OVER THE WESTERN AND
CENTRAL U.S.

A SHOT OF COLD AIR WILL MOVE INTO THE REGION FOR THURSDAY AND
FRIDAY BEHIND THE AFOREMENTIONED CABOOSE SHORTWAVE. THIS WAVE MAY
ALSO SUPPORT AN AREA OF PCPN MOVING WEST TO EAST ACROSS THE STATE
THANKSGIVING DAY. ADDITIONALLY...THIS PUSH OF ENERGY/COLD AIR
SHOULD GENERATE THE USUAL POST FRONTAL LAKE AND OROGRAPHICALLY
ENHANCED SNOW SHOWERS IN THE WAKE OF THE DEPARTING STORM SYSTEM
WITH WESTERN AND NORTHERN AREAS SEEING THE BEST CHANCE OF
SCATTERED LIGHT SNOWS...WHILE THE REST OF THE REGION SEES LITTLE
OR NO SNOW SHOWER ACTIVITY AT ALL.

A BROAD WSW FLOW ALOFT ASSOCIATED WITH THE RISING HEIGHTS WILL
MAKE THIS COLD SHOT TEMPORARY WITH WARMER AIR BEGINNING TO MAKE A
RETURN BY SATURDAY. HIGHS WILL RETURN TO NEAR OR EVEN A TICK ABOVE
NORMAL BY THE WEEKEND BEFORE COOLER AIR APPROACHES AGAIN FOR EARLY
NEXT WEEK.

A FRONTAL SYSTEM IN ADVANCE OF THE WARM AIR WILL MOVE ACROSS THE
STATE ON SUNDAY...BRINGING THE BEST CHANCE OF PCPN DURING THE
PERIOD.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/

LOW PRESSURE CONTINUES TO DEVELOP OFF THE SOUTHEAST COAST LATE
TONIGHT AND WILL STRENGTHEN AS IT LIFTS NWD JUST OFF THE EAST
COAST THROUGH WED NGT. EXPECT RAPIDLY DETERIORATING CONDS FROM
SOUTH TO NORTH DURING THE PREDAWN AND EARLY MORNING HOURS AS SNOW
OVERSPREADS THE AIRSPACE. PCPN WILL LKLY BEGIN AS A MIX IN THE
MDT/LNS AREA BEFORE CHANGING TO ALL SNOW. MOST INTENSE SNOWFALL
RATES AND REDUCED VSBYS WILL BE OVER THE SERN AIRSPACE WITH RATES
UP TO 2"/HR WITH FLGT CATS AOB AIRFIELD MINS. HIGH CONFIDENCE IN
WIDESPREAD IFR CONDS DUSK-DAWN BEFORE SNOW ENDS FROM SW TO NE BY
WED NGT. LOW CIGS SHOULD PERSIST OVER THE WRN 1/3 OF THE AREA WED
NGT WITH MARGINAL IMPROVEMENT ELSEWHERE. AFTER 03Z THURSDAY...CIGS
AND VSBYS SHOULD IMPROVE...BUT SHOULD REMAIN MVFR AT MOST TAF
SITES LATE WEDNESDAY NIGHT. NORTHWESTERLY FLOW BEHIND THE LOW
SHOULD ALLOW IFR TO CONTINUE AT BFD AND JST.

OUTLOOK...

THU...IFR/MVFR WITH OCNL -SHSN WRN 1/3. VFR TO MVFR CIGS
CNTRL/EAST.

FRI...AM MVFR/-SHSN NW...OTHERWISE BCMG VFR.

SAT-SUN...MAINLY VFR. -SHRA PSBL.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 4 AM EST THURSDAY FOR PAZ019-042-
045-046-049>053.
WINTER WEATHER ADVISORY UNTIL 4 AM EST THURSDAY FOR PAZ012-017-
018-037-041.
WINTER STORM WARNING UNTIL MIDNIGHT EST TONIGHT FOR PAZ024>028-
033>036-056>059-063>066.

&&

$$
SYNOPSIS...LA CORTE/STEINBUGL
NEAR TERM...DEVOIR/LA CORTE
SHORT TERM...RXR
LONG TERM...LA CORTE/GARTNER
AVIATION...CERU/STEINBUGL


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