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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 212323
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
723 PM EDT MON APR 21 2014

.SYNOPSIS...
HIGH PRESSURE WILL FINALLY LOSE ITS GRIP OVER THE AREA TONIGHT AS
CLOUDS INCREASE AHEAD OF AN APPROACHING COLD FRONT. SHOWERS AND
PERHAPS A THUNDERSTORM ARE EXPECTED WITH THE FRONTAL PASSAGE ON
TUESDAY...ALONG WITH GUSTY WINDS AND ISOLATED THUNDER. MUCH
COLDER AIR WILL WORK INTO THE COMMONWEALTH FOR TUESDAY NIGHT 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 6 AM TUESDAY MORNING/...
GORGEOUS AFTERNOON IN PROGRESS AS MOSTLY SUNNY SKIES COMBINE WITH
SFC HIGH PRESSURE CENTERED OVER DEL MARVA REGION TO WARM THINGS UP
NICELY. DOWNSLOPING SOUTHERLY WIND ALLOWING WESTERN AND NORTHWEST
PA TO WARM UP THE MOST...WITH TEMPS IN THE LOWER TO MIDDLE 70S
PRESENTLY. MOST PARTS OF CENTRAL PA ARE IN THE MID TO UPPER 60S
WITH A BEAUTIFUL EVENING EXPECTED...AND ONLY SOME INCREASING HIGH
CLOUDS WORKING THEIR WAY EAST AS THE UPPER RIDGE BEGINS TO BREAK
DOWN OVERHEAD.

CLOUDS WILL INCREASE AHEAD OF THE FRONT OVERNIGHT...WITH SHOWERS
LIKELY ACROSS FAR WESTERN AND NORTHWEST BY 12Z. MINS WILL BE MUCH
MILDER THAN RECENT MORNINGS...RANGING THROUGH THE 50S.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
FRONTAL SYSTEM CROSSES CENTRAL PA ON TUESDAY...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. MUCH COLDER AIR DIVES INTO WEST
CENTRAL PA BY 00Z...WITH 850 MB READINGS PLUNGING BELOW ZERO.
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.

&&

.LONG TERM /TUESDAY 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 /00Z TUESDAY THROUGH SATURDAY/...
A WEAKENING RIDGE ALOFT WILL CONTINUE TO BRING VFR CONDITIONS
THROUGH TONIGHT. HIGH CLOUDS WILL INCREASE LATER THIS EVENING...
WITH THICKENING AND LOWERING MID LEVEL CLOUDS AFTER MIDNIGHT.

FOR TUE...A SHORT WAVE AND ASSOCIATED FRONT WILL BRING
RAIN SHOWERS TO PENNSYLVANIA...STARTING IN THE NW BY 12Z. MAY SEE
AN ISOLATED TSTORM IN THE SUSQ VALLEY LATER IN THE DAY. BREEZY NW
WINDS WILL DEVELOP IN THE AFTERNOON...AND CONTINUE INTO WED.


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...DEVOIR/STEINBUGL
NEAR TERM...ROSS/DEVOIR
SHORT TERM...ROSS/DEVOIR
LONG TERM...STEINBUGL
AVIATION...DEVOIR/CERU