FXUS61 KCTP 080217
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
917 PM EST MON DEC 7 2009
.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM WILL MOVE THROUGH THE EASTERN GREAT
LAKES REGION AND DOWN THE SAINT LAWRENCE RIVER VALLEY BY TONIGHT.
A MOISTURE-STARVED COLD FRONT TRAILING SOUTH FROM THE LOW WILL
SWEEP ACROSS THE REGION AND WILL BRING SOME SCATTERED SNOW SHOWERS
TO THE ALLEGHENIES LATE TODAY AND TONIGHT. HIGH PRESSURE WILL
RETURN FOR TUESDAY BRINGING LIGHT WIND AND CHILLY TEMPERATURES
BEFORE A SIGNIFICANT STORM SYSTEM LIFTS NORTHEASTWARD FROM THE
SOUTHERN PLAINS AND BRINGS A PERIOD OF SNOW FOLLOWED BY A WINTRY
MIX OF PRECIPITATION TUESDAY NIGHT INTO WEDNESDAY. MUCH COLDER AIR
WITH A GUSTY WEST WIND WILL FOLLOW FOR THE LATTER PART OF THE
WEEK.
&&
.NEAR TERM /THROUGH TUESDAY/...
THE AREAS OF LIGHT SNOW AND FLURRIES CONTINUES TO DIMINISH...BUT
SEEM TO WANT TO LINGER. A WEAK TROUGH BETWEEN THE TWO ANTICYCLONES IS
MOVING ACROSS CENTRAL PA THIS EVENING. THERE HAVE BEEN SOME GUSTY
WINDS ALONG AND BEHIND THIS SEEMINGLY WEAK FEATURE. GUST IN THE
20-25KT RANGE HAVE BEEN QUITE COMMON. THIS TROUGH WILL TAKE A FEW
MORE HOURS TO GET INTO THE LOWER SUSQUEHANNA VALLEY.
HIGH PRESSURE OVER THE OHIO IS RIDGING INTO WESTERN PA. THIS SHOULD
CONTINUE TO RAISE THE CEILINGS. THERE ARE STILL SOME SITES WELL TO
OUR WEST...IN OH...REPORTING VERY LIGHT SNOW. FLURRY ACTIVITY
COULD LINGER FOR SEVERAL MORE HOURS.
HIGH PRESSURE SHOULD DOMINATE THE REGION BY MORNING. OVERNIGHT
LOWS WILL MAINLY BE IN THE 20S AND 30S. THIS HIGH WILL SLIDE BY
FAST AS THE FAST APPROACHING WAVE TO OUR WEST HAS ALREADY SPREAD
CIRRUS OVER INDIANA AND OH. HAD TO KEEP CLOUDS IN MOST AREAS
TOMORROW AND THEY WILL QUICKLY LOWER AND THICKEN IN THE WEST.
LIGHT SNOW IS POSSIBLE IN THE LATE AFTERNOON OVER SOUTHWESTERN AND
WESTERN SECTIONS. HIGHS WILL MAINLY BE IN THE 30S. WE EXPECT THE
PRECIPITATION TO BEGIN AS SNOW.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
WINTER STORM WATCH HAS BEEN POSTED FROM TUE EVE THRU MIDDAY WED.
CHALLENGING WINTER STORM CONTINUES TO DEVELOP...WITH A HIGH
CONFIDENCE BEST FORCING WILL PAST WELL TO OUR NW ACROSS NORTH-CENTRAL
IN/SE LOWER MI LATE TUE. SFC RIDGE SLIDES WEAKENS MARGINALLY AND
SLIDES NE TOWARDS CANADIAN MARITIME ARND 00Z WED. THIS APPEARS TO
AMPLIFY 285-295K ISENTROPIC LIFT AND 850MB U-WIND ANOMS TO -3 TO -4
STD DEV BY 06Z WED. THERMAL PROFILES SUPPORT ONSET OF MOISTURE
ACROSS OUR SW CWFA TO BE SN...THEN AS WARM AIR ADVECTION INTO
MID-LVLS EXPECT A TRANSITION OVER TO FZRA BY ARND MIDNIGHT TUE NGT.
ENSEMBLES HAVE MAINTAINED HIGHEST ICE ACCRETION PROBS ACROSS THE
LAUREL HIGHLANDS OVERNIGHT TUE/EARLY WED PSBLY EXCEEDING A COUPLE
TENTHS OF AN INCH BEFORE CHANGING TO RA. FURTHER N/NE ICE
ACCRETION WILL BE LOWER AS PERIOD OF SN WILL PERSIST LONGER BEFORE
TURNING TO FZRA/SLEET/RA BEFORE 12Z WED. OVERNIGHT TEMPS WILL
GRADUALLY RISE FROM U20S TO L30S UNDER STRONG SOUTHERLY FLOW.
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/...
HIGH CONFIDENCE REMAINS FRONTAL BNDRY WILL DEPART THE REGION BY 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 AND
GENERATE COOL AND BLUSTERY CONDS. 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.
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 /02Z TUESDAY THROUGH SATURDAY/...
LINGERING VERY LIGHT SNOW AND LOW CLOUDS WILL PERSIST OVER
PORTIONS OF CENTRAL PENNSYLVANIA THIS EVENING THROUGH ABOUT
MIDNIGHT. HIGH PRESSURE AND SOME DRIER AIR SHOULD HELP STOP THE
LIGHT SNOW AND THE CIGS SHOULD SLOW RISE.
HIGH PRESSURE SHOULD PROVIDED FOR LIGHT WINDS AND MOST IF NOT ALL PLACES
GETTING ABOVE 3KFT CIGS AROUND 10 AM. THE STRONG STORM APPROACHING
FROM THE WEST COULD SPREAD LIGHT SNOW INTO SOUTHWESTERN
PENNSYLVANIA BY LATER AFTERNOON AND EVENING. CLOUDS WILL RAPIDLY
THICKEN AND LOWER DURING THE AFTERNOON AND EVENING FROM SOUTHWEST
TO NORTHEAST. PUT PROB30 FOR SNOW AT KJST-KBFD-KAOO-KUNV FOR LATE
IN THE DAY. PRECIPITATION SHOULD HOLD OFF TO THE NORTH AND EAST
UNTIL THE NEXT FORECAST PERIOD.
OUTLOOK...
TUE...SOME IFR BEFORE 14Z...MOSTLY VFR DURING THE DAY. LOWERING TO
MVFR IN SOUTHWEST IN THE AFTERNOON AND EVENING.
TUE NGT/WED...BCMG WDSPRD IFR IN SNOW/ICE/RAIN/FREEZING. RAIN
SHOULD MOVE NORTHWARD FROM SOUTHERN PA IN THE EARLY AM TO AT LEAST
CENTRAL AREAS BY MIDDAY OR EARLY AFTERNOON. SOME AREAS OF LLWS.
AREAS OF VLIFR CIGS AND VSBYS HEAVIER PRECIPITATION. CONDITIONS
SHOULD IMPROVE LATE IN THE DAY AND EVENING TO MVFR IN SOME
LOCATIONS.
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 MTS 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 STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
MORNING FOR PAZ004>006-010>012-017>019-024>028-033>036-045-056-
063-064.
&&
$$
SYNOPSIS...LAMBERT
NEAR TERM...GRUMM
SHORT TERM...BEACHLER
LONG TERM...BEACHLER
AVIATION...GRUMM
