FXUS61 KLWX 070839
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
339 AM EST MON DEC 7 2009
.SYNOPSIS...
A WEAK COLD FRONT WILL PASS THROUGH EARLY THIS EVENING. HIGH
PRESSURE WILL BUILD OVERHEAD TONIGHT INTO TUESDAY. LOW PRESSURE
WILL TRACK THROUGH THE MIDWEST AND INTO THE GREAT LAKES TUESDAY
NIGHT AND WEDNESDAY...BRINGING A GOOD CHANCE FOR RAIN AND WINTRY
PRECIPITATION. HIGH PRESSURE WILL BUILD OVERHEAD LATE IN THE
WEEK...BRINGING DRY AND COLD CONDITIONS.
&&
.NEAR TERM /THROUGH TODAY/...
CLD CVR MOVG THRU FCST AREA ATTM WILL VACATE DURG MRNG. SHRTWV
TROF OVER MS RVR VLY WILL APRCH TDA. LIGHT SFC WINDS EARLY THIS
MRNG WILL STRENGTHEN FROM S IN RESPONSE TO APRCHG WAVE. AS LIFT
INCRS THIS AFTN...MID-LVL CLD CVR XPCD TO INCR. DRY LLVL AIR SHUD
PRECLUDE PCPN MOST AREAS...SPCLY GIVEN XPCD TRACK OF SHRTWV TROF
ACRS PA.
ONLY XCPTN WILL BE UPSLP PORTIONS OF NWRN ZONES CLOSE TO TRACK OF
WAVE. HAVE RETAINED SLGT CHC POPS LATE THIS AFTN AS LLVL INSTBY
INCRS.
MAXIMA TDA WILL BE HINDERED BY RESIDUAL SNOW. HAVE UNDERCUT
GUIDANCE BY SVRL DEG F MOST AREAS...SPCLY WHERE SNOW DEPTH IS
GREATEST.
&&
.SHORT TERM /TONIGHT/...
WEAK CDFNT XPCD TO MOVE THRU FCST AREA EARLY THIS EVE IN RESPONSE
TO PASSING SHRTWV TROF. WNWLY LLVL FLOW WITH FETCH FROM GRTLKS
WILL SUSTAIN LLVL INSTBY THRU LATE TNGT ON WRN SLOPES OF ALLEGHENY
FRONT...SPCLY ALLEGANY...MINERAL AND GRANT CTYS. HAVE RETAINED
HIGHEST POPS NWRN ZONES TNGT FOR SNOW SHOWERS. ELSEWHERE...INCRG
MID- AND UPR-LVL CLDS XPCD AS STRONG UPR LOPRES DIGS INTO SRN PLNS
AND DRAWS MSTR NWD.
CLD CVR WILL LIMIT RADIATIONAL COOLING...BUT SNOW PACK WILL AID
IN BNDRY LYR COOLING TNGT.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
A POTENT LOW PRESSURE SYSTEM WILL DEVELOP EAST OF THE ROCKIES
TUESDAY AND WILL TRACK TOWARD THE GREAT LAKES TUESDAY NIGHT INTO
WEDNESDAY MORNING. THE WARM FRONT ASSOCIATED WITH THIS LOW WILL
MOVE INTO THE REGION OVERNIGHT TUESDAY INTO WEDNESDAY MORNING.
PLENTY OF WARM AND MOIST AIR FROM THE GULF OF MEXICO AND ATLANTIC
OCEAN WILL OVERRUN THE LOW-LEVEL COLD AIR AHEAD OF THE WARM
FRONT...BRINGING PRECIPITATION TO THE REGION. THE MAIN QUESTIONS
ARE HOW MUCH COLD AIR WILL BE IN PLACE...HOW LONG WILL IT REMAIN
IN PLACE...AND WHICH OF SNOW...SLEET...AND FREEZING RAIN WILL
OCCUR. CURRENT FEELING IS THAT PRECIPITATION WILL BEGIN IN THE
FORM OF A WINTRY MIX LATE TUESDAY AFTERNOON/TUESDAY EVENING BEFORE
GRADUALLY CHANGING OVER TO ALL RAIN EARLY WEDNESDAY MORNING. THE
BEST CHANCE FOR SNOW/SLEET ACCUMULATION WILL BE ACROSS THE EASTERN
PANHANDLE OF WEST VIRGINIA INTO WESTERN MARYLAND...AND THE BEST
CHANCE FOR SIGNIFICANT ICING FROM FREEZING RAIN WILL BE FROM THE
BLUE RIDGE MOUNTAINS WESTWARD...INCLUDING EASTERN WEST VIRGINIA
AND WESTERN MARYLAND. ACROSS THE WASHINGTON/BALTIMORE METROPOLITAN
AREAS...PRECIPITATION WILL LIKELY BE IN THE FORM OF RAIN SOUTH AND
EAST OF I-95 WITH A WINTRY MIX NORTH AND WEST OF I-95 CHANGING TO
RAIN. THE BEST CHANCE FOR ANY SIGNIFICANT SNOW/ICE ACCUMULATIONS
WILL BE ACROSS NORTH-CENTRAL MARYLAND NEAR THE MASON DIXON LINE.
DID NOT ISSUE A WATCH WITH THIS FCST DUE TO THE UNCERTAINTY IN
TIMING OF A CHANGE OVER TO RAIN. THIS WILL HAVE A SIGNIFICANT
IMPACT ON ANY SNOW/ICE ACCUMULATIONS. A WATCH SHOULD BE CONSIDERED
STRONGLY FOR LOCATIONS ALONG AND WEST OF THE BLUE RIDGE MOUNTAINS
AND NORTH-CENTRAL MARYLAND NEAR THE MASON DIXON LINE. THE PRIMARY
THREAT APPEARS TO BE SIGNIFICANT ICE ACCUMULATION FROM FREEZING
RAIN...BUT SNOW AND SLEET ACCUMULATION IS POSSIBLE ACROSS EASTERN
WEST VIRGINIA INTO WESTERN AND NORTH-CENTRAL MARYLAND AS WELL.
THE COLD FRONT ASSOCIATED WITH THIS STORM WILL PASS THROUGH
WEDNESDAY AFTERNOON...BRINGING A CHANCE FOR MORE RAIN.
TEMPERATURES WILL BE ABOVE FREEZING ACROSS ALL LOCATIONS BY THIS
TIME. HIGH PRESSURE WILL BUILD IN BEHIND THIS FRONT...BRINGING DRY
AND COLD CONDITIONS WEDNESDAY NIGHT THROUGH FRIDAY ACROSS MOST
LOCATIONS...BUT UPSLOPE SNOW SHOWERS ARE LIKELY WEDNESDAY NIGHT
AND POSSIBLY INTO THURSDAY ALONG AND WEST OF THE ALLEGHENY FRONT.
LOW PRESSURE MAY IMPACT THE REGION FRIDAY NIGHT INTO SATURDAY...
THEN HIGH PRESSURE WILL RETURN SUNDAY.
&&
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
ANY RESIDUAL FOG THIS MRNG WILL LIFT EARLY. CLD CVR XPCD MAINLY IN
MID AND UPR LVLS. VRB WINDS BCM LIGHT SLY BY LATE THIS MRNG IN
ADVANCE OF APRCHG SHRTWV TROF. WIND SHIFT IN ASSOCIATION WITH
PASSING CDFNT XPCD EARLY THIS EVE AS WAVE PASSES. FROPA MAY ALSO
INVIGORATE LLVL CLDS NEAR 3.0 KFT LATE THIS EVE.
VFR CONDITIONS EXPECTED TUESDAY MORNING WITH INCREASING HIGH AND
MID-LEVEL CLOUDS. A WARM FRONT ASSOCIATED WITH LOW PRESSURE MOVING
INTO THE GREAT LAKES WILL BRING SUBVFR CIGS AND VSBYS LATE TUESDAY
AFTERNOON INTO WEDNESDAY MORNING. A WINTRY MIX IS POSSIBLE TUESDAY
EVENING BEFORE PRECIPITATION CHANGES OVER TO RAIN BY WEDNESDAY
MORNING. THE TIMING IN THE CHANGE OVER STILL REMAINS UNCERTAIN AT
THIS TIME. THE PRIMARY THREAT APPEARS TO BE ICING FROM FREEZING RAIN
AND THIS WOULD BE MOST LIKELY AT KMRB.
SUBVFR CIGS AND VSBYS WILL CONTINUE WEDNESDAY AFTERNOON...BUT ANY
PRECIPITATION WILL BE IN THE FORM OF RAIN.
A COLD FRONT WILL PASS LATE WEDNESDAY AFTERNOON...AND HIGH PRESSURE
WILL BRING A RETURN OF VFR CONDITIONS FOR LATE IN THE WEEK. WEST-
NORTHWEST WIND GUSTS AROUND 15 TO 20 KNOTS ARE POSSIBLE WEDNESDAY
NIGHT AND THURSDAY.
&&
.MARINE...
NO MARINE HAZARDS XPCD THRU TNGT...ALTHOUGH NWLY WINDS XPCD TO
INCR LATE TNGT ACRS SRN PORTIONS OF MD CHSPK BAY IN WAKE OF CDFNT
PASSAGE.
HIGH PRESSURE WILL REMAIN OVER THE WATERS TUESDAY. LOW PRESSURE WILL
MOVE INTO THE GREAT LAKES TUESDAY NIGHT INTO WEDNESDAY MORNING. THE
WARM FRONT ASSOCIATED WITH THIS LOW WILL MOVE INTO THE WATERS DURING
THIS TIME. THE COLD FRONT ASSOCIATED WITH THIS LOW WILL PASS THROUGH
LATER WEDNESDAY AFTERNOON. SCA WIND GUSTS ARE POSSIBLE ACROSS
PORTIONS OF THE WATERS TUESDAY NIGHT THROUGH WEDNESDAY AFTERNOON.
SCA THRESHOLD WINDS ALSO ARE POSSIBLE BEHIND THE FRONT WEDNESDAY
NIGHT THROUGH FRIDAY.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
&&
$$
KRAMAR/LASORSA
