FXUS61 KCTP 252352
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
652 PM EST FRI DEC 25 2009
.SYNOPSIS...
A COMPLEX LOW AND ASSOCIATED FRONTAL SYSTEM OVER THE MIDWEST WILL
MOVE SLOWLY EAST OVER THE NEXT FEW DAYS. A PLUME OF DEEP MOISTURE
STREAMING NORTH INTO PENNSYLVANIA WELL AHEAD OF THIS STORM WILL
BRING PERIODS OF RAIN TO THE REGION TONIGHT AND SATURDAY...WITH
GUSTY SOUTHEAST WINDS AFFECTING THE HIGHER ELEVATIONS. AFTER THE
FRONTAL BOUNDARY PUSHES EAST ACROSS THE COMMONWEALTH SATURDAY
AFTERNOON AND EVENING...COLDER AIR WILL MOVE BACK INTO THE STATE
AND PERSIST RIGHT THROUGH NEXT WEEK. A STRONG UPPER DISTURBANCE
WILL CROSS THE AREA ON MONDAY BRINGING NUMEROUS SNOW SHOWERS AND A
FEW HEAVIER SQUALLS...MAINLY ACROSS THE CENTRAL AND NORTHWEST PART
OF THE STATE.
&&
.NEAR TERM /UNTIL 11 PM THIS EVENING/...
RADAR LOOP AND 5 MIN MESO OBS SHOWS BANDS OF ENHANCED RAIN/VIA GRAVITY
WAVES LIFTING NE ACROSS THE REGION. STRONGEST REFLECTIVITY CAUSED
BY SOME BRIGHT-BANDING FROM SLEET AND WET SNOW WAS LOCATED ACROSS
THE NW HALF OF THE CWA. MOST TEMPS ARE IN THE MID 30S...BUT
POCKETS OF TEMPS AROUND 32F AND FZRA WILL CONTINUE INTO THIS
EVENING.
DROPPED THE WINTER WX ADVISORY FROM ALL BUT THE NRN MTNS (WHERE IT
WILL RUN UNTIL 00Z SAT)...AND EVEN THERE MOST TEMPS SHOULD INCH
JUST ABOVE FREEZING AND STAY THERE THROUGH THE OVERNIGHT. A FEW OF
THE PROTECTED VALLEYS WILL LOCK IN THE COLD AIR AND COULD SEE
-FZRA AT TIMES EVEN AFTER MIDNIGHT...BUT NOT WORTH RUNNING THE
ADVISORY THERE BEYOND THE CURRENT 00Z EXPIRATION. TEMPS ACROSS THE
LOWER SUSQ WILL HOVER IN THE MID 30S.
THE OTHER ELEMENT OF IMPACT IN THE NEAR TERM WILL BE THE
STRONG/GUSTY SERLY WIND THAT WILL AFFECT THE RIDGE TOPS OF THE
LAURELS. THERE...GUSTS OF 45 TO 50 MPH WILL BE LIKELY THROUGH THE
FIRST HALF OF TONIGHT...THEREFORE COLLABORATED WITH PBZ AND LWX TO
POST A WIND ADVISORY THROUGH 04Z SAT.
ELSEWHERE...COLD AIR DAMMING THROUGHOUT THE VALLEYS OF CENTRAL
PENN WILL NOT ALLOW STRONGER WIND GUSTS OVER 30 MPH TO MIX DOWN TO
THE SFC.
&&
.SHORT TERM /11 PM THIS EVENING THROUGH SATURDAY NIGHT/...
INCREASING UPPER DIVERGENCE WILL "JUMP" THE APPROACHING OCCLUDED
FRONT AND COLD AIR WEDGE ACROSS THE CENTRAL APPALACHIANS
SATURDAY...AND SPIN-UP A WAVE OF LOW PRESSURE ALONG THE DELMARVA
COAST WHERE THE BEST BAROCLINICITY WILL RESIDE. THIS LOW (AND
INCREASED/DEEP LAYER UVVEL) WILL ENHANCE THE RAINFALL RATES
ACROSS THE REGION SLIGHTLY ON SATURDAY.
MANUAL 36HR STORM TOTAL GRIDDED QPF OF 1.00-1.50 INCHES (THROUGH
00Z SUNDAY) STILL LOOKS IN GOOD SHAPE. THIS...ALONG WITH SNOW
MELT WILL CAUSE MINOR TO MODERATE RISES IN THE WEST BRANCH AND
LOWER SUSQ BASINS...AND MAY PUSH SOME SMALLER TRIBS TO CAUTIONS
STAGE. HYDRO FCSTS FROM THE MARFC DO NOT INDICATE ANY FLOODING
ATTM AND GIVEN THAT ANY PROBLEMS WOULD LKLY NOT OCCUR FOR ANOTHER
36HRS...DECIDED AGAINST A FLOOD WATCH...BUT WL MENTION SOME
SPECIFICS IN HWO AND HYDRO SECTION BELOW.
COLDER AIR WILL BEGIN TO MIX WITH/CHANGE ANY LINGERING RAIN
SHOWERS TO SNOW SHOWERS (WEST DURING THE AFTERNOON) AND LATE SAT
AND SAT NGT (ACROSS THE CENTRAL MTNS AND UPPER SUSQ VALLEY). MINOR
ACCUMS OF UP TO ONE INCH POSSIBLE ACROSS THE MTNS WEST OF A KELM...
TO KUNV AND KAOO LINE.
SKIES WILL PARTIALLY CLEAR OUT SAT NIGHT ACROSS THE RIDGE AND
VALLEY REGION...WITH MORE CLOUDS AND A FEW SHSN LINGERING ACROSS
THE WRN MTNS.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
COLD MID LVL VORT WITH 700/500 MB TEMPS DROPPING TO ABOUT -22/-32
RESPECTIVELY WILL WOBBLE E ACROSS THE OH VLY AND INTO THE MID
ATLC REGION SUN NIGHT THROUGH MONDAY. BRISK/WINDY CONDS AND LES
SHWRS WILL ACCOMPANY A REINFORCING SURGE OF COLDER AIR MON
NGT/TUE. HIGH PRES SHOULD BRING SOME IMPROVEMENT BY THE MIDDLE OF
NEXT WEEK. THIS 36-48 HOUR PERIOD WILL LIKELY CONTAIN SEVERAL
INCHES OF SNOW ACROSS THE LAURELS AND NW MTNS...WITH AN INCH OR TWO
(MAINLY FROM AFTERNOON SNOW SHOWERS AND SQUALLS MONDAY) POSSIBLE
IN THE CENTRAL VALLEYS.
THE MOST TRANQUIL (THOUGH STILL COLD) PERIOD NEXT WEEK WILL BE
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS A LARGE AREA OF HIGH
PRESSURE BUILDS ENE FROM THE OHIO VALLEY.
STRONG NEG AO/NAO...+ PNA AND A SRN STREAM EL NINO CONNECTION
WL CONT TO OFFER A SET UP FAVORABLE FOR EAST COAST WINTER STORMS.
12Z GEFS...AND THE OPERATIONAL 06Z EC/ 12Z GFS STILL SHOW A
DEVELOPING AREA OF LOW PRESSURE MOVING NNE - SEVERAL HUNDRED KM
OFF THE SE AND MID ATLANTIC COAST TOWARD THE START OF THE NEXT
DECADE...STAY TUNED. FOR NOW...WILL BROAD-BRUSH A 30-40 PERCENT
CHC FOR SNOW NEW YEARS EVE INTO THE FIRST DAY OF 2010. 12Z
ECMWF...HAS SHOWN A TYPICAL WWD JOG TO THE PATH OF THE LOW - NOW
CLOSER TO THE MID ATLANTIC COAST...WITH A BETTER CHC FOR SNOW
ACROSS OUR CENTRAL AND ERN ZONES LATE NEW YEARS DAY INTO JAN 2ND.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
STILL DEALING WITH SAME COMPLEX FRONTAL SYSTEM THAT HAS PRODUCED A
MIXTURE OF PRECIPITATION TYPES OVER CENTRAL PA TODAY...HOWEVER
ATTM MAINLY RAIN IS FALLING AT ALL TAF SITES WITH FOG COMMON IN
MANY AREAS. HAVE KEPT SOME LIGHT RAIN AND FOG ALONG WITH LOWER
CEILINGS AT ALL TAF SITES OVERNIGHT. OBS ARE FAIRLY UNSTABLE AND
THUS HAD TO ADD SOME TEMPO GROUPS TO COVER VARIABILITY. EXPECTING
LOW CEILINGS AND VISIBILITIES OVERNIGHT AS RAIN SHIELD CONTINUES TO
MOVE NORTH AND EAST FROM VIRGINIA. HOWEVER SOME IMPROVEMENT IN
CONDITIONS IS EXPECTED AT THE END OF FORECAST PERIOD. IN ADDITION
WINDS ARE STRONG JUST OFF THE SURFACE CREATING THE POTENTIAL FOR
LOW LEVEL WIND SHEAR AND HIGHER GUSTS.
MOST VALLEY LOCATIONS REMAIN COOL AIR DAMMED SO SFC WINDS ARE MAINLY
LIGHT AND OUT OF THE EAST OR SE. EXCEPTIONS ARE OVER HIGHER
WESTERN TERRAIN FROM JST-BFD WHERE GUSTS 20-30KT WILL REMAIN
COMMON.
OUTLOOK...
SAT...IFR CONDITIONS IMPROVING TO MVFR CENTRAL/EAST BY AFTERNOON.
SUN-TUE...MVFR/IFR WEST WITH FREQ LAKE EFFECTING AND OROGRAPHIC
SNOW SHOWERS IN THE WEST. CNTRL/EAST VFR/MVFR WITH SCATTERED SNOW
SHOWERS.
&&
.HYDROLOGY...
GENERALLY MINOR CHANGES IN RIVER LEVELS ARE EXPECTED OVER THE
NEXT 24 HOURS...WITH A RISE OF UP TO SEVERAL FEET EXPECTED LATER
IN THE PERIOD.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR PAZ005-
006-010>012-037-041-042.
WIND ADVISORY UNTIL 11 PM EST THIS EVENING FOR PAZ024-033.
&&
$$
SYNOPSIS...FITZGERALD/LAMBERT
NEAR TERM...LA CORTE/LAMBERT
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD/LAMBERT
AVIATION...ONDREJIK/LA CORTE
HYDROLOGY...
