FXUS61 KCTP 081706
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1153 AM EST TUE DEC 8 2009
.SYNOPSIS...
STRENGTHENING LOW PRESSURE WILL TRACK NORTHEAST FROM THE SOUTHERN
PLAINS THIS AFTERNOON...REACHING THE GREAT LAKES REGION BY
WEDNESDAY. THIS SYSTEM WILL BRING SEVERAL INCHES OF SNOW...AND A
WINTRY MIX OF PRECIPITATION TO MUCH OF CENTRAL PENNSYLVANIA
TONIGHT AND EARLY WEDNESDAY...FOLLOWED BY COLDER AND BLUSTERY
CONDITIONS THURSDAY. HIGH PRESSURE WILL BUILD OVER THE STATE
FRIDAY AND SATURDAY. A STORM SYSTEM MAY PASS SOUTH OF PENNSYLVANIA
LATE SATURDAY OR EARLY SUNDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SFC HI PRESSURE...CURRENTLY LOCATED OVR NORTH CENTRAL PENN AND
THE FINGER LAKES REGION OF NEW YORK...WILL DRIFT NE DURING THE
AFTERNOON. THE FAIRLY LARGE AREA OF BREAKS IN THE DUAL...STRATO CU
AND CIRRUS CLOUD DECK FROM SCENT PENN THROUGH THE SUSQ VALLEY WILL
SEE A THICKENING LAYER OF MID AND HIGH CLOUDS FROM THE SW LATER
THIS AFTERNOON. THIS CLOUD SHIELD IS ADVANCING NE AT 35 TO 40 KTS
AND ITS LEADING EDGE WILL REACH A KMDT TO KUNV LINE AROUND
20Z...THEN OVERSPREAD THE MID SUSQ VALLEY AND NCENT MTNS BETWEEN
21-22Z.
TEMPS WERE BUMPED UP A FEW DEG F THIS AFTERNOON ACROSS THE MID/LWR
SUSQ VALLEY (INTO THE 40-45F RANGE)...AS A RESULT OF THE SEVERAL
HOURS OF PTLY TO MOSTLY SUNNY SKIES.
LATEST...12Z OPERATIONAL MODELS INDICATES LIGHT SNOW WILL
OVERSPREAD SW PENN ARND OR SHORTLY AFTER DUSK...AS OVERRUNNING/WAA
SPREADS EAST IN ADVANCE OF MIDWEST LOW PRES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
TRANSITIONED FROM THE WINTER STORM WATCH TO A WINT WEATHER
ADVISORY FOR MUCH OF THE REGION...WITH AN UPGRADE TO WINTER STORM
WARNING FOR 4 COUNTIES (2 IN THE SW...AND 2 IN THE NW MTNS).
UP TO ONE HALF INCH OF ICE APPEARS LIKELY ACROSS THE HIGHER
TERRAIN OF CAMBRIA AND SOMERSET COUNTIES....WHILE 4 TO 6 INCHES
OF SNOW TOPPED BY AROUND 0.25 OF AN INCH OF ICE SHOULD OCCUR
ACROSS MCKEAN AND POTTER COUNTIES.
VERY GOOD AGREEMENT BETWEEN THE OVERNIGHT U.S. OPERATIONAL
MODELS...GEM...AND EC WITH RESPECT TO 12-18 HOUR SNOW TOTALS OF 4
TO 7 INCHES ACROSS THE NRN MTNS...WITH 2 TO 4 INCHES ACROSS THE
CENTRAL SLICE OF COUNTIES...NEAR AND JUST EAST OF THE ALLEGHENY
FRONT. LITTLE CHANGE IS SEEN ON THE 12Z NAM AND GFS RUNS.
HAVE LEANED MORE TWD THE 12Z NAM FOR PRECIP TYPE...TIMING AND
AMOUNT...COMPARED TO THE GFS WHICH PAINTS A MUCH LARGER AREA OF
HEAVY ICING ACROSS THE CENTRAL RIDGE AND VALLEY REGION.
LEFT OUT AREAS SOUTH AND EAST OF HARRISBURG...WHERE ENS PTYPES
AND MODEL SFC TEMPS DON/T INDICATE MUCH CHC OF FZRA....AND JUST AN
INCH OR TWO OF COMBINED SNOW AND SLEET.
MIN TEMPS IN THE U20S/L30S LIKELY TO BE REALIZED SHORTLY AFTER
ONSET OF PRECIP THIS EVENING...THEN STEADY OR SLOWLY RISING
READINGS THEREAFTER UNDER CAA PATTERN.
WARM AIR ADVECTION WILL CONTINUE WED AS A LLVL 850MB JET IS PROGGED
ARND 40-50KTS PUSHES TEMPS NEAR 40 DEG...WHICH WILL PUSH AN
REMAINING FZRA OVER TO RA ACROSS THE CWFA. CONFIDENCE REMAINS HIGH
THAT A DRY WEDGE LIFTS INTO CENTRAL PA MIDDAY WED...AND COULD CUTOFF
PRECIP FOR MUCH OF THE AFTN. 500MB TROUGH AXIS QUICKLY PIVOTS THRU
MIDDAY WED...HOWEVER IT DOESN/T APPEAR THERMAL RIDGE DEPARTS UNTIL
LATE WED. ISALLOBARIC SFC PRESSURE RISE COUPLET OF ARND 2MB/3-HR IS
PROGGED...WHICH MOST LIKELY WILL FEATURE GUSTY WINDS WED AFTN/EVE
AND STEADILY FALLING TEMPS. ATTM EXPECT UPSLOPE SN/LAKE EFFECT SN
NOT TO OCCUR UNTIL LATE WED...HOWEVER RESONANCE TIME OVER THE LAKES
WILL BE MINIMIZED AT ONSET PROVIDING A CELLULAR LOOK TO PRECIP FOR
NW MTNS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
TRAILING COLD FRONT WILL PUSH THRU THE REGION WED EVE...WITH VERY
INTENSE W/NWSTRLY FLOW PUSHING INTO THE MID-ATLANTIC REGION
THUR/FRI/SAT. FOR SEVERAL DAYS ENSEMBLES GUIDANCE HAS BEEN
POINTING AT 850MB WINDS OF 40-50KTS...UNDER A VERY AGGRESSIVE UPR
LVL JET OF 140-160KTS. THE AFOREMENTIONED ELEMENTS ARE GOING TO
BLEND WITH 850MB TEMPS PROGGED AT -14 TO -16 DEG C THUR/FRI TO
GENERATE COOL AND BLUSTERY CONDS. ATTM FEEL GIVEN CONSID CLOUD COVER
DURING DAYLIGHT HOURS WILL HOLD TEMPS IN THE 20S/30S FOR THE END OF
THE WEEK...HOWEVER IF SKIES CAN CLEAR TEMPS WILL EASILY COOL
OVERNIGHT.
SFC RIDGE IS PRESENTLY ADVERTISED BY ENSEMBLES FOR SAT/SUN...HOWEVER
CONFIDENCE IS LOW ATTM AS IT IS POSSIBLE RIDGE WILL BREAK DOWN
QUICKLY UNDER A PROGRESSIVE W-E FLOW AS A WEEKEND SHORTWAVE TRIES TO
DEVELOP ACROSS THE GULF OF MEXICO STATES. TEMPS REMAIN COOL THRU THE
UPCOMING WEEKEND.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
HIGH PRESSURE SHOULD PROVIDE FOR LIGHT...MAINLY EAST TO SE WINDS
AND VFR CIGS AT ALL AIRFIELDS THROUGH THIS AFTERNOON.
A STRONG STORM APPROACHING FROM THE SOUTHWEST WILL SPREAD A MIX OF
SNOW...SLEET...FREEZING RAIN AND RAIN INTO SOUTHWESTERN
PENNSYLVANIA BY 00Z/9. CLOUDS WILL RAPIDLY THICKEN AND LOWER
DURING THE AFTERNOON AND EVENING FROM SOUTHWEST TO NORTHEAST.
CONDS BCMG WDSPRD IFR IN SNOW/ICE/RAIN/FREEZING TONIGHT. WARM AIR
WILL MOVE INTO THE REGION LATER TONIGHT AND CHANGE PCPN TO MAINLY
RAIN IN THE EARLY AM TO AT LEAST CENTRAL AREAS BY MIDDAY OR EARLY
AFTERNOON. EXPECT AREAS OF LLWS AND AREAS OF VLIFR CIGS AND VSBYS
IN HEAVY PRECIPITATION. CONDITIONS SHOULD IMPROVE LATE IN THE DAY
WEDNESDAY AND EVENING TO MVFR IN SOME LOCATIONS.
OUTLOOK...
WEDNGT/THUR...MVFR/IFR NORTH AND WEST IN SNOW SHOWERS MAINLY IN
THE MOUNTAINS. IMPRVG CENTRAL/EAST TO MAINLY VFR AND MVFR. STRONG
WESTERLY WNDS.
FRI/FRI NIGHT...MVFR WEST WITH SCATTERED SNOW SHOWERS IN MTNS OF
NORTHERN AND WESTERN PA. VFR MOST OF CENTRAL AND EAST.
SAT/SUN...VFR...POSSIBLY DECREASING TO IFR/MVFR SHOULD A SYSTEM
PROVIDE THE REGION WITH LIGHT SNOW.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 11 AM EST
WEDNESDAY FOR PAZ004-010>012-017>019-025>028-034>037-041-042-
045-046-049>053-056>058-063.
WINTER STORM WARNING FROM 7 PM THIS EVENING TO 11 AM EST
WEDNESDAY FOR PAZ005-006-024-033.
&&
$$
SYNOPSIS...FITZGERALD/LAMBERT
NEAR TERM...FITZGERALD/LAMBERT
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD/BEACHLER
AVIATION...LAMBERT/GARTNER
