FXUS61 KLWX 080138
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
838 PM EST MON DEC 7 2009

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE MID ATLANTIC COAST OVERNIGHT 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 /UNTIL 6 AM TUESDAY MORNING/...
SURFACE HIGH PRESSURE OVER THE AREA STARTS TO MOVE EAST OF THE CWA
OVERNIGHT. A WEAK SHORTWAVE MOVES OFF THE COAST THIS EVENING.
MOSTLY CLOUDY SKIES MAY TRANSITION TO PARTIAL CLEARING FOR A WHILE
/EAST OF THE MTNS/ BEHIND THE SHORTWAVE BEFORE HIGH CLOUDS MOVE
BACK IN LATER AT NIGHT. CHANGEABLE SKIES WILL LEAD TO PARTLY TO
MOSTLY CLOUDY CONDITIONS IN THE FORECAST.

NO CHANGES WERE MADE TO POPS/P-TYPE/AMOUNTS WITH THE UPCOMING
STORM TUESDAY NIGHT/WEDNESDAY...HOWEVER INCLUDED RAINFALL/FLOOD
CONCERNS IN ADDITION TO THE WINTER WEATHER POTENTIAL. HPC HAS CWA
IN EXCESSIVE RAINFALL SLIGHT RISK ON DAY TWO.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM 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 /01Z TUESDAY THROUGH SATURDAY/...
VFR SCT-BKN CLOUDS EXPECTED OVERNIGHT INTO TUESDAY MORNING. CIGS
WILL START TO LOWER INTO THE AFTERNOON LIKELY REACHING MVFR TOWARD
LATE AFTERNOON AT KCHO AND TOWARD EVENING ACROSS REMAINING
TERMINALS. THIS WILL BE IN TANDEM WITH PRECIPITATION DEVELOPMENT. 

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...
GRADIENT IS FORECAST TO REMAIN RELATIVELY WEAK TONIGHT...AS WINDS
TURN TO THE NORTHWEST BEHIND A SHORTWAVE. SAME SCENARIO
TUESDAY...BUT LATEST GUIDANCE IS PROJECTING AN INCREASE IN SPEEDS
LATER TUESDAY NIGHT AND ESPECIALLY WEDNESDAY. HAVE RAISED SMALL
CRAFT ADVISORY. SCA CONDITIONS ARE LIKELY TO CONTINUE FOR THE REST
OF THE WEEK.

&&

.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...SMALL CRAFT ADVISORY FROM MIDNIGHT TUESDAY NIGHT TO 5 PM EST 
     WEDNESDAY FOR ANZ530>543.

&&

$$
SYNOPSIS...PELOQUIN/ABW
NEAR TERM...PELOQUIN
SHORT TERM...SBK
LONG TERM...ABW
AVIATION...PELOQUIN/ABW
MARINE...PELOQUIN