FXUS61 KCTP 070020
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
720 PM EST SUN DEC 6 2009
.SYNOPSIS...
HIGH PRESSURE OVER WEST VIRGINIA WILL PUSH EASTWARD TO THE
DELMARVA TONIGHT...AND THEN MOVE OFF THE MID-ATLANTIC COAST ON
MONDAY. MEANWHILE...A WEAK LOW PRESSURE SYSTEM WILL MOVE THROUGH
THE GREAT LAKES AND UP THE SAINT LAWRENCE RIVER VALLEY BY MONDAY
NIGHT. A MOISTURE-STARVED COLD FRONT TRAILING THE LOW WILL SWEEP
ACROSS THE REGION AND MAY BRING SOME SCATTERED SNOW SHOWERS TO THE
ALLEGHENIES LATER MONDAY AND INTO MONDAY NIGHT. HIGH PRESSURE WILL
RETURN FOR TUESDAY BEFORE A SIGNIFICANT STORM SYSTEM LIFTS
NORTHEASTWARD FROM THE CENTRAL U.S. BRINGS A MIXTURE OF
PRECIPITATION TUESDAY NIGHT INTO WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
REMAINING CU/SC WILL DISSIPATE THROUGH SUNSET...GIVING WAY TO INC
MID AND HIGH CLOUDS AHEAD OF SHEARING MIDWEST SHORTWV TROUGH AND
DVLPG MID MS VLY SFC LOW. AFTN TEMPS HAVE LIKELY REACHED THEIR
MAX +/- A DEGREE OR TWO...AND WILL BEGIN TO DROP OFF INTO THE EVE
HOURS. QUESTION FOR THE OVERNIGHT WILL BE WHETHER WAA ALOFT AND
THICKENING CLOUDS CAN COUNTER FRESH SNOW COVER AND SOMEWHAT LESS
THAN IDEAL RADIATIONAL COOLING. WITH THE VEIL OF LYRD MID AND
HIGH CLOUDS POISED TO MOVE IN FROM THE SW...DECIDED TO PLAY A
MIDDLE GROUND FOR MINS...ADDING A FEW DEGS TO DEWPOINTS AND
BLENDING WITH LATEST GUID. FEEL THAT WAA IS NOT STRONG ENOUGH FOR
NON-DIURNAL TREND...BUT TEMPS SHOULD STEADY SOME AFT MIDNIGHT AS
LLVL WNDS VEER AROUND TO THE S/W.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
HIGH PRES INITIALLY OVR THE DELMARVA WILL SLIDE OFF THE MID-ATLC
COAST IN ADVANCE OF WEAK LOW AND TRAILING COLD/OCCLD FNT MOVING
EWD ACROSS THE GREAT LKS/OH VLY. DESPITE DECENT KINEMATIC FORCING
ALOFT ASSOC WITH AN 100KT JET SURGING ENEWD FM THE MS
VLY...VERY LIMITED LLVL MSTR/LOW PWS SUPPORTS BARELY MEASURABLE
QPF WITH THIS SYS. THEREFORE WILL CONFINE CHC POPS ONLY THE
ALLEGHENIES...WHERE OROGRAPHICS WILL PROVIDE SOME ADDITIONAL LIFT
NEEDED TO PERHAPS SQUEEZE OUT A FEW TENTHS. POST-FNTL LK MSTR TAP
MAY TOO AID IN GENERATING SCT SNOW SHOWER ACTIVITY...ESP HEADING
INTO MON NGT.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
MINIMAL ADJUSTMENTS TO GOING EXTENDED PERIODS. CONFIDENCE REMAINS
VERY HIGH WITH MID-WEEK STORM. MON NIGHT THRU TUE WILL FEATURE A
QUIET PERIOD...WITH WEAK SFC RIDGE PROVIDING ANTI-CYCLONIC FLOW IN
THE BNDRY LYR WITH P-CLOUDY SKIES FOR MUCH OF THE CWFA. WEAK
DOWNSLOPING WILL PROVIDE FURTHER EROSION OF CLOUDS LEE-SIDE OF THE
ALLEGHENIES TUE. HIGH LVL MOISTURE QUICKLY POOLS NE AHEAD OF
DEVELOPING STORM TUE NGT.
PRECIP MOVES IN TUE NGT AS A WEAK FRONTAL BNDRY LIFTS NORTH AHEAD OF
DEEPENING SURFACE LOW WHICH WILL TRACK NE THROUGH OHIO VALLEY.
CENTRAL PA WILL REMAIN ON E SIDE OF THE LOW...WHICH WILL EVENTUALLY
PUSH WARM AIR INTO THE REGION. BUT TUE NIGHT WHEN PRECIP BEGINS
TEMPS SHOULD BE COLD ENOUGH TO START OFF AS SNOW...AND COULD SEE A
COUPLE OF INCHES ACCUMULATE. BUT WARM AIR WILL STREAK IN AS TEMPS
WARM ABV FREEZING BY 12Z WED IN THE SOUTH AND A COUPLE OF HOURS
LATER IN THE NORTH. ENSEMBLES HAVE HELD ONTO QPF ARND .5 TO .7
INCHES...WITH ONSET PSBLY MIXING WITH FZRA ACROSS THE SOUTH. TROUGH
DOES BECOME MORE NEGATIVELY TILTED LATER WED INTO THU AS A COASTAL
LOW FORMS OFF NEW ENGLAND COAST...BUT ENSEMBLE SUGGESTS SFC VORT
SHUD PASS NW OF THE CWA BY THEN. THIS COULD PROVIDE A BRIEF BREAK IN
PRECIP WED AFTN AHEAD OF FRONTAL PASSAGE.
FLOW REMAINS VERY PROGRESSIVE WITH SEVERAL GEFS MEMBERS ADVERTISING
A 130-150KT 300MB JET THUR/FRI. THIS SHUD PROVIDE A GOOD SCENARIO IN
THE BNDRY LYR FOR LES ACROSS THE NW MTNS/UPSLOPE SNOW FOR LAUREL
HIGHLANDS. 850MB TEMPS CONSIDERABLY COOLER AT -12 TO -14 DEG C
THUR/FRI. ATTM FEEL GIVEN CONSID CLOUD COVER DURING DAYLIGHT HOURS
TEMPS WILL HOLD IN THE 20S/30S FOR THE END OF THE WEEK...HOWEVER IF
SKIES CAN CLEAR TEMPS WILL EASILY COOL OVERNIGHT.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
VFR CONDS WILL CONTINUE OVERNIGHT WITH SFC HIGH PRESSURE CENTERED
ALONG THE MID ATLANTIC COAST. MID LEVEL WARM ADVECTION ABOVE A
VERY DRY BOUNDARY LAYER (WITH SFC DEWPOINTS IN THE MID TEENS TO
LOWER 20S) WILL CREATE VARYING AMOUNTS OF MID AND HIGH CLOUDS
TONIGHT...BASED BETWEEN 15-20 KFT AGL. LIGHT AND VARIABLE SFC
WINDS WILL PREVAIL THROUGH 12Z MONDAY...BEFORE VEERING AROUND TO
THE SOUTH DURING THE MID TO LATE MORNING HOURS. SOUTH TO SE WINDS
OF 5 KTS OR LESS THROUGHOUT THE CENTRAL VALLEYS AND SUSQUEHANNA
REGION MONDAY MORNING...WILL VEER TO THE SOUTHWEST IN THE
AFTERNOON. WIND SPEEDS DURING THE DAY MONDAY WILL BE ABOUT 3-4KTS
HIGHER ACROSS THE WRN PENN MTNS.
WK SFC LOW LIFTING NEWD ACROSS THE GRT LKS AND UP THE ST LAWRENCE
VLY WILL PUSH A COLD/OCCLD FNTL SYS THRU THE REGION BY MON NGT.
GUID SUGGESTS CIGS TO LWR AOB 5KFT AT JST/BFD BY LATE MORNING AND
CONTINUE TO DETERIORATE THRU MON NGT BCMG MVFR/IFR. CONFIDENCE IS
FAIRLY HIGH WRT TO THE LOW CIG RESTRICTIONS ESP POST FROPA AS LLVL
FLOW BECOMES ALIGNED WITH THE LAKE AND ASCENDS THE HIER TERRAIN.
SOME SCT -SHSN ARE ALSO PSBL. UNV/AOO/IPT SHUD STAY MVFR OR BETTER
WHILE MDT WILL REMAIN VFR. HIGH PRES MOVES IN FOR TUE BUT LOW
CLOUDS LKLY TO HANG TOUGH IN THE WEST. SIGNIFICANT STORM SYSTEM
FCST TO MOVE THROUGH THE GRT LKS WILL BRING A MIXTURE OF PCPN TUE
NGT INTO WED WITH WDSPRD IFR LKLY. STRONG WINDS ALSO APPEAR A GOOD
BET ON THURS THE ATTENDANT COLD/OCCLD FNT RACES NEWD OFF THE
ECOAST. NWLY FLOW IN THE WAKE OF THIS SYS MAY KEEP REDUCED CIGS
AND VSBYS ACROSS THE WESTERN HIGH TERRAIN ALONG WITH SOME LAKE
EFFECT SNOW SHOWERS.
OUTLOOK...
MON...SCT AFTN MVFR/IFR IN SHSN NORTH/WEST. VFR/MVFR CENTRAL/EAST.
TUE...MVFR/IFR BCMG VFR NORTH/WEST. MVFR BCMG VFR CENTRAL/EAST.
TUENGT/WED...BCMG WDSPRD IFR IN SNOW/ICE. LLWS.
WEDNGT/THUR...MVFR/IFR WEST. IMPRVG CENTRAL/EAST. STRONG WSW WNDS.
FRI...MVFR WEST. VFR EAST.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...STEINBUGL
NEAR TERM...STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...BEACHLER/RXR
AVIATION...LAMBERT/STEINBUGL
