FXUS61 KCTP 231233
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
733 AM EST WED DEC 23 2009
.SYNOPSIS...
LOW PRESSURE WILL DROP SOUTHEAST THROUGH NEW YORK TODAY. HIGH
PRESSURE WILL BRIEFLY BUILD INTO THE REGION THROUGH THURSDAY
BEFORE A STRONG LOW PRESSURE SYSTEM OVER THE MIDWEST CREATES A
POTENTIALLY ICY START TO CHRISTMAS DAY. THE PRECIPITATION FROM
THIS STORM SHOULD TURN TO PLAIN RAIN BY LATE IN THE DAY
FRIDAY...AND LAST INTO SATURDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPPER LOW MOVING ACROSS NY WILL CONTINUE LK EFF SHSN OVER MOST OF
WRN NY AND SOME FLURRIES ARE EXPECTED TO SPILL INTO THE NRN MTS.
BUT NO ACCUMS ARE LIKELY. THERE IS ALSO A CHANNEL OF
CLOUDS/FLURRIES ALONG A MID LVL TEMP GRADIENT FM KTOL TO KJST. THIS
SRN MSTR AND CLOUD COVER IS EXPECTED TO SINK SWRD THROUGH THE
MORNING. SO...MOST OF THE REGION WILL END UP MO SUNNY
TODAY...EXCEPT THE NRN TIER. THIS WILL HELP TEMPS TO NEAR FREEZING
IN THE SERN VALLEYS...BUT MOST OF THE AREA WILL STAY AOB 30F...AS
8H TEMPS STAY STEADY AROUND -4C IN THE SW AND -10C IN THE NE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
FAVORABLE LK TRAJS FOR LLVL WINDS AND AN UPPER VORT STREAM LEFT
BEHIND BY THE DEPARTING UPR LOW WILL CONTINUE TO MAKE
CLOUDS/FLURRIES IN THE NE TONIGHT...AND PERHAPS INTO THURS AM.
1036MB HIGH PRESSURE OVER CENTRAL CANADA AND DROPPING TEMPS THERE
INTO THE TEENS BLO F GRADUALLY NOSES DOWN INTO THE AREA TONIGHT
AND THURS. THE HIGH SETS UP OVER QUEBEC...WHICH IS NOT A USUAL
PLACE FOR AN ANTICYCLONE TO CREATE TERRIBLE COLD AIR DAMMING. BUT
THE STRENGTH OF THE HIGH CLIMBS TO NEAR 1040MB. THIS WILL SUPPLY A
DECENT AMOUNT OF SHALLOW COLD AIR INTO THE NRN APPALACHIANS TO DAM
UP THE LOCAL AREA SUFFICIENTLY TO CREATE AN INTERESTING SCENARIO
LATE CHRISTMAS EVE AND CHRISTMAS DAY.
STORM DROPPING OUT OF BC WILL PHASE WITH A SYSTEM OVER THE WRN
U.S. AND AMPLIFY A TROF OVER THE CENTRAL STATES...WRAPPING UP A
BIG STORM OVER THE NRN PLAINS. WHILE THE LOW AT THE SFC AND ALOFT
WILL REMAIN WELL TO THE WEST OF THE REGION...IT WILL BEGIN TO DRAW
AMPLE WARM AIR INTO THE AREA FROM THE SOUTH. BUT...THE DAMMING
SHOULD HOLD ON AND THE ADVECTION WILL ALL BE ALOFT INITIALLY. THE
LLVL FLOW WILL BE VERY MUCH E/SE AND THE OROGRAPHICS OF CENTRAL PA
WILL HELP TO CREATE LOW STRATUS AND PERHAPS SOME DZ LATE CHRISTMAS
EVE. THE CLOUDS WILL HELP KEEP TEMPS UP A BIT CHRISTMAS EVE...BUT
STILL BELOW FREEZING ALL NIGHT.
THE LIFT AND GULF MSTR WILL MAKE FOR RAIN WHICH WILL MOVE UP THE
OH VLY...BUT AS IT GETS NEARER TO THE AREA...IT WILL INTERACT WITH
THE LOCAL TEMP PROFILE TO MAKE SOME FREEZING RAIN AND EVEN A
LITTLE SNOW CHRISTMAS /FRI/ MORNING. THE MOST LIKELY SCENARIO
MOVES THE STEADY PRECIP IN AROUND SUNRISE FRI AND SPREADS LIGHT
RAIN THRU THE ENTIRE AREA DURING THE DAY. TROUBLE...AGAIN...IS THE
SHALLOW SUB-FREEZING LAYER THAT SHOULD BE IN PLACE. ESP BECAUSE
THE PRECIP AND CLOUDS SHOULD ARRIVE IN THE MORNING...DAYTIME
HEATING MAY BE THWARTED AND ANY WARM-UP WILL BE PRIMARILY FROM
ALOFT/MIXING AS THE PRECIP FALLS. ATTM...IT IS STILL A LITTLE
EARLY TO MAKE DEFINITE CALLS AS TO AMT OF FZRA OR SN
EXPECTED...BUT CONFIDENCE GROWS TO ALMOST CERTAINTY THAT WE WILL
EVENTUALLY NEED ADVSRY FOR FZRA OVER MUCH OF THE AREA. PRECIP
LOOKS LIGHT ENUF THAT WE SHOULD NOT SEE 0.25IN OF ICE THAT WE
WOULD NEED TO EXPECT TO POST A WARNING...SO I WILL NOT POST A
WATCH ATTM. SIGNIFICANCE OF THIS LIGHT FZRA IS THE TRAVEL IMPACT
IT MAY CREATE. IT IS HOWEVER...IN DAY3 TIME FRAME...STILL FAR
ENOUGH OUT IN THE FUTURE FOR SOME CHANGES TO THE FCST. STAY TUNED.
MOST OF THE AREA SHOULD RISE ABV FZG BY 2PM FRI AND CHANGE THE
MESSY STUFF TO PLAIN RAIN. EVEN THO THERE MAY BE AN INCH OF LIQUID
OVER THE DEEP SNOWPACK OF THE SRN TIER/LWR SUSQ...EXPECT RIVER
FLOODING TO BE VERY TOUGH TO COME BY. THIS IS MAINLY DUE TO THE
LOW FLOWS ATTM...BUT ALSO TO THE FACT THAT SOME OF THE RAIN COULD
JUST BE SOAKED UP BY THE SNOW. BUT LOCAL PROBLEMS MAY ARISE AS
DRAINS MAY BE CLOGGED AND SNOWMELT WILL ADD TO THE RUN OFF. SOME
SHSN WILL START LATE FRI NIGHT OR SAT AM IN THE WRN HIGH TERRAIN
AS THE COLDER/DRIER AIR WRAPS IN FM THE SW. THE REST OF THE AREA
SHOULD SEE A COLD...CONSTANT RAIN FRI NITE AND SAT.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
COLDER AIR WILL BLAST INTO THE AREA FROM THE WEST SAT NGT...LKLY
CHANGING ANY PCPN OVER TO SNOW/SHWRS. THE SHARP GRADIENTS AND LLVL
WIND FIELDS COULD MAKE FOR STRONG WINDS NEAR COLD/OCCLD FNT. A
MEAN UPPER TROUGH TAKES HOLD OVER MUCH OF THE ERN U.S. INTO EARLY
NEXT WEEK WITH CYC FLOW KEEPING SCT LES SHWRS OVER THE WESTERN AND
NORTHERN MNTS. AN UNSETTLED PATTERN MAY UNFOLD TWD THE NEW YEAR AS
IT APPEARS THE SRN STREAM WILL REMAIN ACTIVE.
&&
.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
WHILE VFR CONDITIONS WILL PERSIST FOR MOST AIRFIELDS...JST/BFD
WILL HAVE PERIODS OF LOWER CONDITIONS...PERHAPS EVEN A FEW
FLURRIES. HAD SOME STRANGE WEATHER YESTERDAY ACROSS THE
LAUREL HIGHLANDS YESTERDAY...NOT SURE IF IT WAS FREEZING
DRIZZLE. WILL WATCH THIS MORNING. THE OTHER THING TODAY
WILL BE THE WIND...IT WILL LIKELY COME UP SOME...AS THE
UPPER LEVEL LOW DROPS SE.
THE STORM FOR CHRISTMAS IS NOW FORECAST TO BE SLOWER.
STILL COME CONCERN FOR MIXED PCPN EARLY ON. STILL THINK
IT WILL WARM UP...BUT NOT BY MUCH...AS THE STORM TRACKS
TOO FAR WEST...AND THERE IS A DECENT SNOWPACK TO THE SE.
WILL ALSO HAVE TO WATCH FOR LOWER CLDS AND FREEZING DRIZZLE
AHEAD OF THE MAIN SYSTEM...GIVEN SE FLOW.
A LOT OF DIRECTIONAL SHEAR BEHIND THE FRONT...SO HARD
TO SEE VERY MUCH ACTION OFF THE LAKES.
OUTLOOK...
THU...VFR WITH POCKETS OF MVFR/IFR ACROSS ALLEGHENIES.
FRI...POOR FLYING CONDS. WIDESPREAD IFR TEMPO LIFR WEST/CENTRAL.
MVFR EAST. FZRA/SN EARLY THEN RA. LINGERING FZRA EAST TURNING RA
LATE.
SAT...MVFR/SCT IFR. SHSN WEST.
SUN...MVFR/IFR WEST W/SHSN. PATCHY VFR/MVFR EAST.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...DANGELO
NEAR TERM...DANGELO
SHORT TERM...DANGELO
LONG TERM...DANGELO/STEINBUGL
AVIATION...BEACHLER/MARTIN
