Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 220555
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
155 AM EDT TUE APR 22 2014

.SYNOPSIS...
CLOUDS WILL THICKEN UP ACROSS THE REGION THIS MORNING AHEAD OF AN
APPROACHING COLD FRONT. SHOWERS AND PERHAPS A THUNDERSTORM ARE
EXPECTED WITH THE FRONTAL PASSAGE TODAY. MUCH COLDER AIR WILL
WORK INTO THE COMMONWEALTH TONIGHT AND WEDNESDAY...WITH LAKE
EFFECT SNOW SHOWERS OVER THE NORTHWEST AND WEST CENTRAL MOUNTAINS
AND FLURRIES POSSIBLE OVER THE REST OF THE CENTRAL AND NORTHERN
MOUNTAINS. A COOL...BUT MAINLY DRY PERIOD IS EXPECTED WEDNESDAY
AND THURSDAY...WITH HIGH PRESSURE RETURNING TO THE AREA. THE NEXT
COLD FRONT AND ASSOCIATED RAIN CHANCES ARE FORECAST TO ARRIVE ON
FRIDAY.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
THICKENING MID AND HI CLOUDS /AND A LIGHT SWRLY SFC WIND/ SPREADING
ACROSS CENTRAL AND WESTERN PENN ATTM WILL GREATLY TRIM THE TEMP
DROP FOR THE REST OF THE OVERNIGHT HOURS /WITH MINS BETWEEN
50-55F/...WHILE MAINLY CLEAR SKIES ACROSS THE FAR SOUTHEAST ZONES
WILL ALLOW TEMPS TO FALL SEVERAL MORE DEG F...TO THE MID AND UPPER
40S.

CONSENSUS ON PRECIP TIMING REMAINS RIGHT AROUND SUNRISE OR A
LITTLE LATER IN THE NW. GFS BRINGS SPRINKLES IN A LITTLE
FASTER...BUT IT IS THE OUTLIER. ANY SHOWERS BEFORE 12Z WILL BE
VERY LIGHT...MOST LIKELY FALLING FROM A MID CLOUD BASE THROUGH A
DEEP LAYER OF DRY AIR.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
COLD FRONT CROSSES CENTRAL PA TODAY...AND TIMING OF FROPA FROM
15Z TO 20Z IS SUPPORTIVE OF THUNDER ACCOMPANYING THE FRONT.
INSTABILITY STILL APPEARS TO BE LACKING AT THIS TIME
HOWEVER...WITH MUCAPES ONLY IN THE 300-450 J/KG RANGE...LIKELY
LIMITED BY SFC DEWPOINTS. STILL...THE INSTABILITY WILL BE
SUFFICIENT TO MIX DOWN SOME 25 TO 35KT GUSTS AND EXPECT TO SEE A
NARROW COLD FRONTAL RAINBAND FEATURE WITH THE FROPA. NOT LOOKING
FOR ANYTHING SEVERE...THOUGH SMALL HAIL MAY BE POSSIBLE WITH
STRONG JET MAX AND RAPIDLY COOLING TEMPS ALOFT.

MAXES WILL OCCUR MID TO LATE MORNING TO EARLY AFTERNOON...WITH
HIGHS RANGING FROM THE MID 50S NORTHWEST TO AROUND 70 SOUTHEAST.

MUCH COLDER AIR DIVES INTO WEST CENTRAL PA BY 00Z WED...WITH 850
MB READINGS PLUNGING BELOW ZERO.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
SFC LOW OVER NORTHERN NEW ENGLAND AT 00Z WED WILL DEEPEN INTO THE
CANADIAN MARITIMES THROUGH DAY 3/WED...AS THE PARENT UPPER LEVEL
TROUGH AMPLIFIES SEWD ACROSS THE NORTHEASTERN CONUS AND EVENTUALLY
CLOSES-OFF NEAR THE GULF OF MAINE/SOUTH OF NOVA SCOTIA BY 12Z
THURS. THIS SHOULD MARK THE BEGINNING OF A LARGER SCALE PATTERN
TRANSITION FROM MODERATELY PROGRESSIVE TO A BLOCKY/SLOWER-EVOLVING
REGIME BY THE WEEKEND AND INTO EARLY NEXT WEEK.

FRONTAL RAIN SHOWERS SHOULD EXIT THE ERN 1/3 OF THE CWA LATE TUES
EVE/EARLY TUES NIGHT. GUSTY POST-FRONTAL WNW FLOW WILL INCREASE
THROUGH WEDNESDAY AND HELP DIRECT AN ABNORMALLY COOL CANADIAN
AIRMASS INTO THE AREA FOR THE MIDDLE OF THE WEEK. DAYTIME HIGHS
ON WEDNESDAY WILL AVG 5-10 DEGREES BELOW NORMAL WITH A GRADUAL
REBOUND ON THURSDAY. CAN/T RULE OUT SOME SNOW SHOWERS DOWNWIND OF
LAKE ERIE AND OVER THE WESTERN HIGH TERRAIN WEDNESDAY MORNING.
SFC HIGH PRES RIDGE AXIS WILL CROSS THE AREA ON THURSDAY. AT THIS
TIME IT APPEARS THAT THERE WILL BE ENOUGH OF A PRES GRADIENT AND
NW WIND TO PREVENT FROST/FREEZE HEADLINES FOR THE LOWER SUSQ.
VALLEY THURSDAY MORNING.

THERE IS DECENT MODEL/ENSEMBLE AGREEMENT IN A SHORTWAVE TROUGH AND
SFC LOW PRESSURE TRACKING THROUGH THE GREAT LAKES REGION BY THE
END OF THE WEEK...WITH THE NEXT COLD FRONT FCST TO ARRIVE ON
FRIDAY ACCOMPANIED BY THE CHC FOR SHOWERS. THERE IS INCREASING
SPREAD IN THE GUIDANCE FOR THE WEEKEND AND INTO EARLY NEXT WEEK
WITH HINTS OF A REX BLOCK DEVELOPING OVER THE CENTRAL NOAM AND
MEAN TROUGH LINGERING OVER SERN CANADA AND PERHAPS THE NERN US.
THE 21/12Z GFS ARE STRONGLY IN FAVOR OF THIS EVOLUTION WHILE THE
21/00Z ECMWF AND 21/12Z GEFS ARE NOT QUITE AS AMPLIFIED WITH
TROUGHING OVER SERN CANADA/NERN US. DUE TO THE VARIABILITY IN THE
GUIDANCE...OPTED FOR A CONSENSUS BLEND FOR MAX/MIN/POP WHICH
RESULTED IN NEAR NORMAL TEMPS AND RELATIVELY LOW PROBS FOR RAIN.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
A WEAKENING RIDGE ALOFT WILL CONTINUE TO BRING VFR CONDITIONS
THROUGH THE PREDAWN HOURS...WITH THICKENING/LOWERING MID LEVEL
CLOUDS.

FOR THE DAYLIGHT HOURS TODAY...A SHORT WAVE AND ASSOCIATED COLD
FRONT WILL BRING RAIN SHOWERS TO PENNSYLVANIA...STARTING IN THE
NW BY 12Z. EXPECT MVFR CIGS AND VSBYS THROUGH 22Z MAY SEE AN
ISOLATED TSTORM IN THE SUSQ VALLEY LATER IN THE DAY. THIS COULD
BRING IFR CIGS AND VSBYS BETWEEN 15-21Z. BREEZY NW WINDS WILL
DEVELOP IN THE AFTERNOON...AND CONTINUE INTO WED WITH WIND GUSTS
UPWARDS OF 25 MPH IN THE AFTERNOON.


OUTLOOK...

TUE...SEVERAL-HOUR PERIOD OF MVFR CIGS POSS WITH BRIEF MVFR VSBYS
IN SHOWERS ACCOMPANYING A COLD FRONTAL PASSAGE. BREEZY NW WINDS
DEVELOPING LATE.

TUE NIGHT-WED...MVFR NORTH/WEST WITH SCT -SHRA...VFR ELSEWHERE.
BREEZY NW WINDS.

THU...VFR. NO SIG WX.

FRI...MVFR WITH CHC SHRA.

SAT...MVFR WITH CHC SHRA

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...ROSS/DEVOIR
LONG TERM...STEINBUGL
AVIATION...LAMBERT/CERU


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