FXUS61 KCTP 142100
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
400 PM EST MON DEC 14 2009
.SYNOPSIS...
A RIDGE OF HIGH PRESSURE OVER THE COMMONWEALTH TODAY WILL DRIFT
OFFSHORE TONIGHT ALLOWING A COLD FRONT TO PASS EARLY TUESDAY
FOLLOWED BY AN EXTENDED PERIOD OF BELOW NORMAL TEMPERATURES...AND
MOUNTAIN SNOW SHOWERS RIGHT INTO THE UPCOMING WEEKEND. AN AREA OF
LOW PRESSURE MAY DEVELOP ALONG THE SOUTHEAST COAST OF THE U.S.
SATURDAY NIGHT AND MOVE NORTHEAST...BRINGING A CHANCE FOR SOME
SNOW SUNDAY INTO MONDAY.
&&
.NEAR TERM /THROUGH TUESDAY/...
VIZ SATELLITE SHOWS PLENTY OF CLOUDINESS STREAMING IN AHEAD OF THE
APPROACHING FRONT HOWEVER SFC OBS INDICATE LITTLE IN THE WAY OF
PRECIP REACHING THE GROUND UPSTREAM. SHORT TERM MODEL QPF IS ON
THE VERY LIGHT SIDE AND THAT LOOKS REASONABLE GIVEN THE
THE CONDITIONS TO OUR WEST.
THE OVERNIGHT LOOKS CLOUDY AND MILD WITH THE BEST CHANCE OF PRECIP
OVER THE WESTERN HIGH TERRAIN FROM ABOUT MIDNIGHT ON. INITIALLY
ITS WARM ENUF ALOFT TO SUPPORT RAIN BUT DURING THE LATE MORNING
HOURS WE SEE DEEP ENUF COLD AIR MOVING IN TO CREATE A CHANGE TO
SNOW SHOWERS OVER THE NORTHWEST. I PUT A RAIN/SNOW MIX ELSEWHERE.
THE WESTERLY FLOW AND FAIRLY DRY UPSTREAM CONDITIONS ARGUE FOR A
SHARP DROP OFF IN POPS AS WE MOVE INTO CENTRAL AND EASTERN
AREAS...SO FOR TUES AFTERNOON I MENTIONED LITTLE MORE THAN
SCATTERED SPRINKLES OR FLURRIES OVER CENTRAL AREAS INTO THE
NORTHERN PARTS OF THE SUSQ VALLEY. TEMPS WILL NOT REALLY DROP OFF
UNTIL LATER IN THE DAY AND OVERNIGHT SO ANOTHER RELATIVELY MILD
DAY IS IN STORE.
&&
.SHORT TERM /TUESDAY NIGHT/...
TROUGH AXIS SWINGS THRU MID-ATLANTIC REGION AS FRONTAL BNDRY IS
POISED TO PASS THRU PA EARLIER IN THE DAY...WITH A STEADY FEED OF
COOLER AIR FILTERING INTO THE REGION. BNDRY LYR MOISTURE REMAINS
SHALLOW UNTIL LATE AFTN/EVE...ONCE A WEAK VORT LOBE PIVOTS ARND
TROUGH AXIS EARLY WED. THIS SHUD ELEVATE INVERSION HEIGHTS FOR THE
NW MTNS...WITH MOISTURE ARRIVING IN THE DGZ OR ARND THE -20DEG C
LYR. THUS STILL ANTICIPATE THAT LGT ACCUMS TUE NGT...THEN AGAIN FOR
WED. ATTM IT APPEARS SUB-ADVISORY CRITERIA...HOWEVER A FEW
LOCAL/HIGH TERRAIN AREAS COULD REACH CRITERIA. TEMPS WILL FALL INTO
THE U-TEENS/L20S NW...M20S/U20S ELSEWHERE.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
GUIDANCE SUGGESTS A PERSISTENT PATTERN ARRIVING BEHIND FRONTAL
PASSAGE TUE FOR WED THRU EARLY NEXT WEEK. CONFIDENCE BEGINNING TO
INCREASE WITH RESPECT TO BLOCK OVER GREENLAND HOLDING THRU THE
WEEKEND. EXPECT MID-LVL TROUGH TO ALSO MAINTAIN ITSELF ACROSS
ONTARIO/QUEBEC...WHICH MAY ALLOW FOR WEAK VORT LOBES TO SLIDE SE
FROM CENTRAL CANADA ACROSS THE GREAT LAKES REGION AND EVENTUALLY
INTO THE MID-ATLANTIC.
THE WILDCARD FOR THE SECOND HALF OF THE WEEKEND WILL BE THE
INFLUENCE OF THE NORTH ATLANTIC BLOCK...AND POTENTIAL FOR A
RETROGRADING 500MB VORT MAX INTO ONTARIO. A FEW GUIDANCE MEMBES HINT
AT THIS SCENARIO...HOWEVER THE OVERALL CONFIDENCE IS THAT A
CONTINUED NW FLOW PATTERN WILL MAINTAIN COOL CONDS. PRECIP APPEARS
MINIMAL AS WELL. EXPECT DOWNSLOPING TO KEEP MINIMAL CLOUD COVER
ACROSS THE SUSQ-VALLEY FOR THE AFTN HRS...WITH CONTINUED UPSLOPE AND
LAKE EFFECT CLOUDS ACROSS THE ALLEGHENIES/NW MTNS. MAX TEMPS SHUD
REMAIN UNIFORM FOR NEXT SEVERAL DAYS... ARND 30S TO U20S
NW/CENTRAL...L30S/M30S FOR REMAINDER OF CWFA OVER THE WEEKEND/EARLY
NEXT WEEK. OVERNIGHT LOWS WILL BE MAINLY IN THE TEENS/L20S...M20S
ACROSS THE LOWER SUSQ-VALLEY FOR THE EXTENDED.
&&
.AVIATION /21Z MONDAY THROUGH SATURDAY/...
MOST CENTRAL AND EASTERN AREAS ARE NOW VFR WITH CIGS MAINLY ABOVE
5000'. STILL IFR OVER NW PA WHERE BFD WANTS TO HANG ONTO A CIG
UNDER 1000'. THE OVERNIGHT SHUD WEE CEILINGS LOWER IN ALL AREAS
AHEAD OF THE APPROACHING FRONT...WITH MVFR/IFR DEVELOPING OVER ALL
OF THE AREA BETWEEN ABOUT 6PM AND MIDNIGHT LOCAL TIME.
TUESDAY WILL SEE THE WORST CONDITIONS OVER THE HIGH TERRAIN OF THE
WEST AND NW WITH SCATTERED RAIN CHANGING TO SNOW SHOWERS.
ELSEWHERE JUST SCATTERED FLURRIES OR SPRINKLES AND POSSIBLY BRIEF
MVFR CIGS IN THE MORNING INTO THE EARLY AFTERNOON. BULK OF THE
TIME SHUD BE VFR HOWEVER. WIND S WILL BECOME GUSTY LATER IN THE
DAY AND INTO TUESDAY NIGHT AS A STRONG HIGH BUILDS IN FROM THE
OHIO VALLEY AND TIGHTENS THE GRADIENT. GUSTS TO BETWEEN 20 AND
30KT WILL BECOME COMMON INTO WED.
OUTLOOK...
WED...MVFR IN -SHSN WEST. MAINLY VFR ELSEWHERE. GUSTY WNW WNDS.
THU/FRI...BCMG VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LA CORTE
NEAR TERM...LA CORTE
SHORT TERM...BEACHLER
LONG TERM...BEACHLER
AVIATION...LA CORTE
