FXUS61 KCTP 141916
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
216 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/...
DEEPEST COLD AIR WILL OCCUR TUESDAY AFTERNOON INTO WED
MORNING...WHEN THE SUBSIDENCE INVERSION WILL BE 7-8 KFT AGL ACROSS
THE WRN/NRN HIGH TERRAIN. THIS WILL SUPPORT NUMEROUS SNOW
SHOWERS...OVER THE INTERIOR NW AND LAUREL HIGHLANDS...WITH SOME
LOCALLY HEAVIER LES ACROSS WARREN AND MCKEAN COUNTIES.
WE SPREAD OUT THE "SEVERAL INCHES" OF SNOW ACCUMULATION OVER A 24
HOUR PERIOD FOR NOW. LATER SHIFTS CAN BETTER FINE-TUNE THE AMOUNTS
AND THE PERIOD OF MORE SIGNIFICANT SNOWFALL...TO DECIDE WHETHER AN
ADVISORY IS NEEDED FOR TUESDAY AFTERNOON INTO WED ACROSS A FEW
COUNTIES OF THE NW AND LAURELS.
EXPECT ONLY THE OCCASIONAL FLURRY OR VERY BRIEF/ISOLATED SNOW
SHOWERS TO ROAM THE CENTRAL RIDGE AND VALLEY REGION DURING THIS
PERIOD.
THE MOST NOTICEABLE ASPECT OF THE WEATHER TUESDAY THROUGH THURSDAY
WILL BE THE GUSTY NW WIND. TOP OF THE MIXED LAYER WILL TAP AN
OCCASIONAL 30 KT GUST.
MAX TEMPS WILL BE ACHIEVED DURING THE EARLY MORNING ACROSS THE
WEST...AND LATE MORNING THROUGHOUT MOST OF CENTRAL AND ERN PENN.
READINGS WILL BE STEADY OR SLOWLY FALLING IN THE AFTERNOON AS 925 TO
850 MB TEMPS DROP BY 4-6C BETWEEN 12Z TUE AND 00Z WED.
MIN AT DAYBREAK WED WILL RANGE FROM THE UTEENS ACROSS THE NRN MTNS
TO BETWEEN 25-30F IN THE VALLEYS. HIGHS WED WILL BE 3-5F BELOW
NORMAL...RANGING FROM THE MID AND UPR 20S ACROSS THE NRN AND WRN
MTNS...TO THE U30S IN THE SOUTHEAST.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
SPRAWLING SFC HIGH PRESSURE AREA BECOMES LOCATED ACROSS THE CENTRAL
APPALACHIANS FOR THURSDAY THROUGH FRIDAY. A FEW...WEAK SHORTWAVES
EMBEDDED IN THE FAST NW FLOW ALOFT WILL BRING SOME MINOR VARIATIONS
TO CLOUD COVER AND THE CHC FOR SNOW SHOWERS. COLDEST TEMPS WILL
OCCUR FRIDAY AND SAT MORNING...WHEN LOWS WILL BE IN THE UPPER
SINGLES DIGITS TO LOWER TEENS ACROSS THE NORTH...AND MID TEENS TO
LOWER 20S IN MOST OTHER AREAS. LARGER CITIES IN THE SE COULD HOLD IN
THE MID 20S FOR LOWS.
TEMPS WILL STAY SEVERAL DEG F OR MORE BELOW NORMAL RIGHT THROUGH THE
WEEKEND.
00Z ECMWF AND SEVERAL GEFS MEMBERS ARE NOW TRENDING TOWARD A
SIGNIF UPPER TROUGH BREAKING OFF/PIVOTING AROUND THE SLOWLY
RETROGRADING/DEEP SERN CANADA CLOSED LOWS(S)...AND LIFTING IN A NEG
TILT FASHION FROM THE SE US...TWD THE MID ATLANTIC COAST.
OPERATIONAL GFS IS A BIT WEAKER/FURTHER OFFSHORE WITH THE SFC
LOW...AND SHOWS A FLATTER SHORT WAVE ALOFT (MAINTAINING MORE A
COLD/DRY NW FLOW AT THE SFC AND ALOFT ACROSS PENN).
INCLUDED A CHC FOR LIGHT SNOW SUNDAY INTO MONDAY ACROSS MUCH OF THE
REGION FOR NOW...TO PLAY THE MID GROUND BETWEEN MODEL SOLUTIONS
SINCE THERE IS MUCH UNCERTAINTY IN BOTH LOCATION AND TIMING OF THE
POSSIBLE ECOAST WINTER WX EVENT. GEFS PLUMES SUGGEST THE OCCURRENCE
OF THIS POTENTIAL WINTER STORM ANYWHERE FROM SAT NIGHT TO TUESDAY.
&&
.AVIATION /19Z 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...LAMBERT
LONG TERM...LAMBERT/GARTNER
AVIATION...LA CORTE
