FXUS61 KCTP 040228
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
928 PM EST THU DEC 3 2009
.SYNOPSIS...
A DEEP STORM OVER NORTHERN MAINE EARLY THIS AFTERNOON...WILL
CONTINUE OFF INTO THE CANADIAN MARITIMES TONIGHT. IN ITS WAKE A
NOTICEABLY COLDER AIRMASS WILL MOVE INTO THE REGION ON A GUSTY
WEST WIND. HIGH PRESSURE WILL PROVIDE MAINLY DRY CONDITIONS FOR
FRIDAY BEFORE ANOTHER STORM MOVING JUST OFF THE EAST COAST BRINGS
THE POTENTIAL FOR SOME SNOW SATURDAY.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
PERVASIVE STRATUS IN MODERATE COLD ADVECTION WEST OF THE
ALLEGHENIES IS BREAKING UP IN THE WNW DOWNSLOPE FLOW OVER CENTRAL
AND SOUTHEAST PA. BREEZY CONDITIONS WILL CONTINUE INTO LATE
EVENING BEFORE DECREASING AFTER MIDNIGHT AS SFC RIDGE AXIS BUILDS
ACROSS CENTRAL AND SOUTHERN PA BY 12Z FRI. EXPECT SKY COVER TO
REMAIN PRETTY CLOSE TO WHAT WE HAVE NOW FOR THE OVERNIGHT...ALONG
WITH SCATTERED SHOW SHOWERS ACROSS THE WEST AND NORTH...AND MIXED
RAIN/SNOW SHOWERS OR SPRINKLES/FLURRIES CHANGING TO SCATTERED SNOW
SHOWERS OR FLURRIES ACROSS THE CENTRAL MOUNTAINS.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
WITH MODELS SHOWING DECENT LOW LEVEL ANTICYCLONIC FLOW AND
FORECAST SOUNDINGS SHOWING A PERSISTENT INVERSION...IT COULD BE
HARD TO SEE SIG IMPROVEMENT IN SKY CONDITION FRIDAY. AS A RESULT
I KEPT A RATHER PESSIMISTIC CLOUD FORECAST FOR MUCH OF THE DAY FOR
MOST OF WESTERN PA. AT THIS TIME OF YEAR WE CAN NEVER RULE OUT
SOME LIGHT PRECIP OVER THE UPSLOPE AREAS OF THE WEST...BUT THE
INVERSION SHOULD BE LOW ENUF TO PRECLUDE ANYTHING SIGNIFICANT.
FRIDAY WILL STILL BE BREEZY FOR MUCH OF THE DAY...WITH HIGHS NEAR
OR SLIGHTLY BELOW SEASONAL NORMS.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
MAIN CONCERN IS FOR THE EVOLUTION OF A SFC LOW OVER SOUTH TEXAS IN
THE NEXT 24 HOURS...AND ITS IMPACT ON THE MID ATLANTIC STATES AND
PERHAPS SOUTHERN AND EASTERN PA SATURDAY AFTERNOON INTO SUNDAY.
THE TIMING AND STRENGTH OF THE UPPER TROF NOW ALONG THE SOUTHERN
BRITISH COLUMBIA COAST...COMBINED WITH STRENGTH AND DIGGING OF
POLAR SHORTWAVE DROPPING THROUGH THE NORTHERN PLAINS AND NORTHERN
ROCKIES HELPING TO KICK OUT UPPER TROF CURRENTLY OVER THE 4
CORNERS REGION WILL DETERMINE HOW MUCH PA IS AFFECTED BY MID
ATLANTIC COASTAL STORMINESS SATURDAY AND SATURDAY NIGHT.
TREND OVER THE PAST 24 HOURS IS FOR MEMBERS OF THE GEFS TO BE
SLIGHTLY CLOSER TO THE MID ATLANTIC COAST ON SATURDAY WITH THE
CENTER OF LOW PRESSURE...WHICH INDUCES LIGHT SNOWFALL FURTHER
INLAND THAN RUNS FROM 24-36 HOURS AGO. SHOULD THIS SYSTEM BE ABLE
TO DEVELOP SOME DEEPER CONVECTION OVER THE GULF COAST REGION
FRIDAY INTO FRIDAY NIGHT...THIS TREND MAY CONTINUE INCREASING THE
LIKELIHOOD FOR LIGHT SNOW TO PUSH FURTHER NORTH AND WEST INTO MY
FORECAST AREA. AS IT STANDS NOW...00Z NAM12 (ARRIVING NOW)
CONTINUES PRESENT THINKING THAT SOME LIGHT SNOWFALL MAY DEVELOP
OVER THE SOUTHEAST HALF OF PENNSYLVANIA SATURDAY AFTERNOON AND
EVENING WITH THE POTENTIAL ANYWAY FOR SOME LIGHT ACCUMULATION
ESPECIALLY SOUTHEAST OF HARRISBURG. THE SFC LOW TRACKS EAST OF
CAPE COD TOWARDS NOVA SCOTIA LATE SATURDAY NIGHT WITH ANY SNOWFALL
ENDING BEFORE SUNRISE SUNDAY.
ONCE THAT LOW GOES BY...HIGH PRES REMAINS IN CONTROL OF REGIONAL
WEATHER SUNDAY. WEAKER SHORTWAVE SLIPS THROUGH MON AND MAY BRING
A SHOT OF SOME LIGHT SNOW TO THE NW. BUT FOCUS TURNING TO WED AS
CONFIDENCE FAIRLY HIGH /EVEN AT THIS TIME RANGE/ FOR POTENTIAL
STORM SYSTEM REACHING PA TUE NIGHT-WED NIGHT. THIS LOW HAS BEEN
PROGGED FOR A FEW DAYS NOW...AND LOOKS TO BE FAIRLY POTENT. AT
THIS TIME IT APPEARS THERE WILL BE ENOUGH WARM AIR AHEAD OF IT FOR
IT TO BE MAINLY A RAIN EVENT WITH SOME SNOW MIXING IN AT TIMES.
MREFS ALSO INDICATE POTENTIAL FOR A NOTICABLE BLAST OF COLDER AIR
BEHIND THIS SYSTEM FOR LATE NEXT WEEK...ALTHOUGH COLD AIR IN PLACE
OVER W CANADA HAVING TROUBLE PUSHING SOUTHWARD THUS FAR.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
PRETTY TYPICAL COLD SEASON POST FRONTAL PATTERN IN PLACE OVER THE
AREA WITH MVFR CEILINGS AND SCATTERED LIGHT SHOWERS OVER CENTRAL
AND WESTERN TERMINALS...WITH VFR FURTHER EAST OVER THE SUSQ
VALLEY.
BFD/JST STAND THE BEST CHANCE OF SOME TEMPORARY IFR CIGS THIS
EVENING GIVEN THEIR HIGHER ELEVATION. WESTERLY FLOW NOT CONDUCIVE
TO DRAW ABUNDANT LAKE MOISTURE INTO PA...SO WILL ANY -SHSNRA OVR
AT BFD AND JST WILL BE SCT AT BEST AND VSBYS SHOULD REMAIN
PREDOMINANTLY P6SM.
RESIDUAL LAKE EFFECT STRATOCU SHOULD LIFT TO VFR BY AFTN AT
BFD/JST...AS SFC RIDGE BUILDS OVR THE AREA.
OUTLOOK...
SAT...POTENTIAL SNOWFALL COULD PRODUCE MVFR/IFR ACROSS SOUTHERN PA.
SUN...VFR.
MON...CHC SHSNRA WEST. VFR LIKELY EAST.
TUE...CHC MVFR CIGS WEST. VFR LIKELY EAST.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LA CORTE
NEAR TERM...LA CORTE/DEVOIR
SHORT TERM...LA CORTE
LONG TERM...RXR/DEVOIR
AVIATION...FITZGERALD
