FXUS61 KCTP 040904
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
404 AM EST FRI DEC 4 2009
.SYNOPSIS...
HIGH PRESSURE WILL PROVIDE MAINLY DRY CONDITIONS TODAY AND
TONIGHT. AN UPPER LEVEL DISTURBANCE TRANSLATING EASTWARD ACROSS
THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS WILL SPAWN AN AREA OF
LOW PRESSURE OF THE NORTH CAROLINA COAST...WHICH COULD BRING SOME
LIGHT SNOW TO PARTS OF SOUTH CENTRAL AND SOUTHEASTERN PENNSYLVANIA
ON SATURDAY. HIGH PRESSURE WILL BRING A RETURN TO FAIR WEATHER FOR
SUNDAY.
&&
.NEAR TERM /TODAY/...
WESTERLY FLOW WILL BE MAINTAINED THRU MUCH OF THE PD AS SFC RIDGE
AXIS EXTENDS NEWD FROM THE TN VALLEY. COLDER AIR WILL ADVANCE SLOWLY
EWD ON THE WRLY FLOW FROM UPR TROF AXIS OVER CENTRAL U.S. WITH
WRLY FLOW ANY LE ACTIVITY WILL BE CONFINED TO FAR NW COUNTIES...SO
MOST AREAS WILL BE DRY.
&&
.SHORT TERM /TONIGHT/...
MODEL GUIDANCE CONTINUES TO SHOW A SRN STREAM WAVE LIFTING NE ALONG
THE MID ATLC COAST. ATTM HOWEVER...IT APPEARS THAT ANY SIG PCPN WILL
HOLD OFF OVER CENTRAL TIL AFTER 12Z SAT.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
MODEL AND ENSEMBLE GUID CONTINUES TO DEPICT A FAIRLY VIGOROUS
SHORTWAVE TROUGH TRANSLATING EWD FM SERN TX ACROSS THE LWR MS VLY
AND INTO THE GULF COAST/SOUTHEAST STATES BY 05/12Z. THIS
DISTURBANCE WILL INDUCE A SFC WAVE ALONG THE WRN ATLC GULF
STREAM...WHICH IS FCST TO BECOME SLIGHTLY BETTER ORGANIZED AS IT
LIFTS NNEWD TWD THE NEW ENGLAND BENCHMARK BY 06/00Z. THE NAM SOLN
CONTINUES TO BE ON THE DEEPER/AMPLIFIED SIDE OF THE SOLN SPREAD
ALOFT...RESULTING IN A MORE WWD SFC LOW TRACK WHEN COMPARED TO THE
OTHER GUIDANCE. HPC PREFERS A COMPROMISE BTWN THE 00Z ECMWF/UKMET
AND 21Z SREF MEAN BOTH ALOFT AND FOR SFC LOW TRACK....WITH
AMPLITUDE SIMILAR TO OR SLIGHTLY DEEPER THAN THE GFS. THERE ARE
STILL SOME TIMING ISSUES TO BE RESOLVED AS THE GFS AND ITS
ENSEMBLE MEAN ARE GENERALLY ON THE FASTER EDGE OF THE
ENVELOPE...MOST NOTABLY IN THE 12HR PERIOD ENDING 06/00Z OUTPACING
THE LATEST GUIDANCE TO THE NORTH AND EAST. OVERALL...MADE LITTLE
CHANGE TO THE GOING FCST AND WILL CONTINUE THE IDEA OF A STRIPE OF
LIGHT SNOW POSSIBLE NW OF SREF MEAN H85 LOW TRACK /PERHAPS WITHIN
A FAVORABLE REGION OF MID LVL DEFORMATION OR FGEN BANDING BENEATH
THE SLIGHTLY NEGATIVE TILT-PROGRESSIVE UPPER TROUGH/...BRUSHING
THE FAR SCENTRAL AND SERN ZONES WITH UP TO AN INCH OF ACCUM.
DESPITE MARGINAL BLYR TEMPS ESP OVR THE LWR SUSQ VLY...BOTH THE
NAM AND GFS FCST SNDGS...ALONG WITH THE 03Z SREF PLUMES SUPPORT
ALL SNOW AT MDT WITH ABOUT A 50/50 MIX OF RAIN AND SNOW MEMBERS AT
LNS. GIVEN THE UNCERTAINTY WILL STILL HOLD POPS MAINLY IN THE HIGH
CHC CATG WITH THE EXCEPTION OF AREAS ALONG AND SOUTH OF U.S. RT
30...WHERE A MANUAL BLEND OF QPF...WEIGHTED HEAVILY TWD THE SREF
AND HPC SUPPORT A SLIGHT INC OF ABOUT 5-10 PCT TO LKLY CATG.
HIGH PRES WILL PROVIDE FAIR WX SAT NGT THRU SUN...SLIDING NEWD FM
THE OH VLY AND OFF THE MID ATLC COAST BY EARLY MON. A LARGE SCALE
PATTERN CHANGE IS LOOMING UPSTREAM INTO NEXT WEEK...WITH
STRONG/BUILDING AK RIDGING AND DEEP NEGATIVE PAC NW HEIGHT ANOMALY
PROGGED TO EVOLVE DOWNSTREAM INTO A VERY INTENSE /-3 TO -4SD/ SFC
CYC LIFTING NEWD FROM THE MID MS VLY TO THE GREAT LKS BY NEXT
WED/THUR.
&&
.AVIATION /07Z 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/STEINBUGL
NEAR TERM...GARTNER
SHORT TERM...GARTNER
LONG TERM...STEINBUGL
AVIATION...GARTNER
