FXUS61 KLWX 072003
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
303 PM EST MON DEC 7 2009
.SYNOPSIS...
HIGH PRESSURE 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 FREEZING RAIN. HIGH
PRESSURE WILL BUILD OVERHEAD FOR THE SECOND HALF OF THE WEEK.
&&
.NEAR TERM /TONIGHT/...
SHRTWV PASSING N OF THE AREA LT THIS AFTN AND EVE. SYNOPTIC LIFT
AIDED BY OROGRAPHIC FEATURE ENUF TO PRODUCE LGT SHSN W OF ALLEGHENY
FRONT...AND THIS SHUD CONT THRU ERY TUE MORN. OTHERWISE...CWA WILL
RMN DRY AS HIPRES TO THE N KEEPS LL INVRN IN PLACE. SOME CLEARING
BETWEEN THIS EVES SHRTWV AND SHIELD OF HIGH CLDS ADVANCING NEWD WITH
SUBTROPICAL JET...ALLOWING FOR SOME RADIATIONAL COOLING...PARTICULARLY
IN SERN CWA...WHERE THERE IS NO SNOWPACK TO AIDE IN DIURNAL COOLING.
LOW TEMPS XPCD TO BE IN L-U20S W OF BLUE RIDGE...WITH U20S-L30S E.
LGT SLY WDS THIS EVE WILL BCMG LGT NW BY MDNGT AFTER SHRTWV
PASSES...REINFORCING HIPRES TO THE NORTH.
&&
.SHORT TERM /TUESDAY/...
UPR TROF DIGS DEEP INTO PLAIN SYSTEMS...ALLOWING LOPRES TO EMERGE E
OF ROCKIES AND INTENSIFY. AS THE TROF DEEPENS...SLY JET INCRS ACRS
ERN CONUS...BRINGING WAA AND ABUNDANT MOISTURE NWD TO THE MID-ATLC.
AT THE SURFACE...HIPRES WILL WEDGE DOWN THE ERN SIDE OF THE
APPALACHIANS...KEEPING COLD TEMPERATURES AND NLY FLOW AT THE
SURFACE. CONSIDERABLE MID/HIGH CLD CVR WILL GRADUALLY THROUGH THE
DAY AS COLD DRY LAYER AT THE SFC BCMS MORE SHALLOW. AS SFC WARM
FRONT SLOWLY DRAWS NWD OVER THE CAROLINAS...PRECIP SHIELD ASSOCIATED
WITH ISENTROPIC LIFT IN ADVANCE OF IT WILL SPREAD INTO SWRN CWA
FIRST...LIKELY IN EARLY AFTERNOON...AND REACH NEWD TOWARD MD/VA
BORDER BY SUNSET. THE DEPTH OF THE COLD BOUNDARY LAYER WILL BE
CRITICAL IN DETERMINING WHAT PRECIPITATION TYPE FALLS. THE BOUNDARY
LAYER WILL CONTINUE TO BECOME MORE SHALLOW...SO EVEN THROUGH
PRECIPITATION WILL LIKELY BEGIN AS A PERIOD OF SLEET OR EVEN
SNOW...IT WILL GRADUALLY BEGIN TO TRANSITION TO RAIN. TEMPERATURES
TOMORROW ARE XPCD TO BE ABOVE FREEZING WITH ONSET OF
PRECIPITATION...SO LITTLE IN THE WAY OF ACCUMULATION IS XPCD BEFORE
SUNSET TUE.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
TUE NGT SHAPING UP TO BE QUITE A CHALLENGE TO FCST. I'VE WRITTEN
ABOUT THE LOW PRES IN THE CENTER OF THE COUNTRY REACHING MI BY WED
MRNG FOR THE PAST COUPLE OF DAYS NOW...SO THE MAP DSCN IS IN PRETTY
GOOD SHAPE. LET'S GET TO THE NUTS AND BOLTS - AM STILL WORRIED ABT
THE PTNL FOR SIG ICING TUE NGT...ESPECIALLY W OF RTE 15. THERE ARE
SOME THINGS THAT LEAD TOWARD ME KEEPING ACCRETION TOTALS ON THE
LOWER SIDE - THE POSN OF THE HIGH TO THE N IS NOT THE BEST FOR
KEEPING COLD AIR LOCKED AT THE SFC. ANOTHER IS THE CALENDAR...IF
INDEED A SECONDARY LOW FORMS TUE EVENING IT WILL DRAW ERLY WINDS
INTO THE RGN...IF THIS WAS JAN OR FEB I WOULDN'T BE SO CONCERNED...
BUT CHES BAY WATER TEMPS ARE STILL THE U40S SO IT WL BE EASY TO DRAW
WARMER AIR INTO THE ERN PART OF THE CWA.
I'VE STATED WHY I THINK SOME PLACES HV CHCS OF ONLY LGT AMTS OF
ICE...BUT I'M STILL CONCERNED ABT A LENGTHY PD OF SUB FRZG TEMPS IN
THE VALLEYS W OF RT 15...AS WELL AS ALONG THE MD/PA BORDER. AND I'VE
SEEN IT SO MANY TIMES WHERE THE MDLS DON'T DO A GOOD JOB OF HOLDING
ONTO SUB 1300 M 850-000 THCKNS...SO WHILE THE GFS SHOWS THE KINKING
OF THE 850-000 THCKNS LNS ALONG THE E SIDE OF THE BLUE RDG IT ALSO
SHOWS THCKNS ARND 1308 ACROSS ALLEGANY CO BY 12Z WED...AND OF THE
2ND PART I GET SUSPICIOUS. BLV IT WL BE PSBL FOR THE SUB FRZG AIR TO
HANG ON FOR A FEW HRS IN THE NW PART OF THE CWA WED MRNG. ACCUM OF
G.T. 1/4" ICE IS PSBL.
I'LL BE HONEST - I'VE SPENT THE MAJORITY OF MY DAY ON THIS STORM AND
HAVEN'T DWELLED ON MUCH IN THE LATER PDS. HIGH PRES LOOKS TO MOVE
INTO THE AREA FOR THE 2ND HALF OF THE WK. ATMOSPHERE IS VERY
ENERGETIC...AND THERE COULD BE A SYSTEM CARRIED ON THE SRN STREAM
LATE IN THE WKND...BUT THAT'S A LONG WAY AWAY.
&&
.AVIATION /TONIGHT THROUGH SATURDAY/...
SCT/BKN CLD DECKS AROUND 4KFT...10KFT...AND 20KFT...WILL CONTINUE
THROUGH TNGT INTO TMRW MRNG. AS STORM SYSTEM APPROACHES FROM THE SW
BY TUE AFTN...LOWER CLOUDS AND EVENTUALLY A WINTER MIX OF
PRECIPITATION SHUD BEGIN BY TMRW EVNG. HOWEVER...THROUGH 24/30HR TAF
PERIODS...VFR CONDS PREVAIL. LGT SW WINDS THIS EVE BCM LGT NW
OVNGT...THEN NE BY TUE MRNG.
TUE NGT LOOKS TO BE A BAD ONE FOR FLYING. FZRA MAY NOT BE MUCH OF
PROBLEM AT DCA/BWI..BUT IT MAY AT IAD/CHO TUE NGT. SUB VFR SKIES
XPCTD AT ALL SITES TUE NGT AND ERLY WED.
&&
.MARINE...
WEAK PRESSURE GRADIENT/CDFNT WILL MOVE ACRS THE WATERS BEFORE
MIDNIGHT...PRODUCING A SURGE OF NLY WINDS AT 10-15 KT FOR A SEVERAL
HOUR PERIOD. SCA THRESHOLDS NOT XPCD TO BE REACHED. NLY WINDS AOB 10
KT XPCD TO CONT THRU TUE.
SCA WINDS XPCTD ON WED AND THU.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
MORNING FOR MDZ003>005-009-501-502.
VA...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
MORNING FOR VAZ021-025>031-036>042.
WV...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
MORNING FOR WVZ050>055-501>504.
MARINE...NONE.
&&
$$
PRODUCTS...SBK/WOODY!
