Winter Weather in Virginia, December 9, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
143 AM EST FRI DEC 9 2005

.SHORT TERM (REST OF TODAY)...
UPDATED THE ZONES TO REFLECT CURRENT OBSERVATIONS. ALSO TWEAKED
THE WSW A BIT. WARM NOSE ALOFT HAS MOVED IN ACROSS THE PIEDMONT
AREAS OF NORTHERN AND OBSERVATIONS FROM THAT REGION HAVE BEEN
REPORTING PREDOMINANTLY FREEZING RAIN AND SLEET. ICE
ACCUMULATION OF ONE QUARTER OF AN INCH WILL BE LIKELY.

&&

.PREVIOUS DISCUSSION...
(ISSUED 850 PM EST THU DEC 8 2005)

UPDATE...ILL SAY THIS...THE TAX PAYER HAS GOTTEN THEIR MONEYS
WORTH OUT OF MY FCSTG PARTNER AND I DURING THIS SET OF 7
SHIFTS...AND MOTHER NATURE HAS SAVED THE BEST FOR LAST. THE OVRNGT
FCST IS QUITE DIFFICULT...AND A DEG OR TWO DIFFERENCE IN THE LO LVL
ATMOPSHERE WL MEAN A WORLD OF DIFFERENCE THRU FRI MRNG.

A PHONE CALL JUST CAME IN - 10SM N WINCHESTER VA THAT S- JUST
BEGAN. MID ATLC RDR LOOP SHOWS SN IS MAKING A STEADY EWD PROGRESSION
- AT 7 PM S- BEGAN IN GRANT CO. INTERESTING TO NOTE THAT THE HOUR
PRIOR TEMP DROPPED 5 DEGS AT EKN ONCE S- BEGAN. ATMOPSHERE HAS BEEN
VERY DRY (SPL 18Z SNDGS AT IAD AND PBZ SHOWED A PW OF ONLY 1/4. 00Z
SNDGS HV ONLY GONE UP 1/10 OF AN INCH) SO INTRODUCTION OF MOISTURE
W/ SN CAUSED A QUICK COOLING OF THE COLUMN. THIS SHOULD CONTINUE AS
THE MOISTURE SPREADS E. *HOWEVER*...THERE IS BIG CONCERN REGARDING
THE STNG PROGGED 850-800 MB WIND FIELD..S AT 50 KT RIGHT DURG TIME
OF PEAK PCPN (06-12Z). THIS IS ACTUALLY SEEN IN THE 00Z RNK SNDG.
THIS WL PUSH THE ABV SFC TEMPS ABV FRZNG. QUESTIONS STILL RESIDE
CONCERNING HOW FAR W THIS CHG COULD OCCUR..AND FOR HOW LONG. HENCE
THE PSBLTY RMNS FOR SGNFT ICING. DAYSHIFT PCPN GRIDDS HAD A GOOD
HANDLE ON WHAT I THINK COULD HAPPEN - A MIX OF ALL THREE WINTER
PCPNS FM DC-CHO AND PTS E. HV ADDED A SLIVER OF IP ADJACENT W OF
THAT AREA BTWN 09-12Z. 850 0 LN IN 00Z ANLYS IS APRCHG LWR SRN MD.
HV CHGD THE PCPN TO PLAIN R THERE A FEW HRS EARLIER.

I WL HV TO REISSUE THE WSW THIS EVE. ONE THING I WL MAKE IS TO CHG
ANY ICE ACCUM WL BE MINIMAL TO SOME ICE ACCUM IS PSBL. CHO TO
SRN FAUQUIER LOOK TO BE THE MOST PROBLEMATIC.

I PLAN TO WAIT UNTIL CLOSE TO 10 PM TO RELEASE PRODUCTS TO SEE HOW
THINGS ARE TRANSPIRING AND ACT ACCORDINGLY.

WOODY

SHORT TERM...
CMPLX FCST SCENARIO SETTING UP...W/ BOTH NRN AND SRN STREAM SYSTMS
AFFECTING CWFA TNGT/TMRW. MANY VARIABLE TO CONSIDER. ATTM...HIPRES
STILL OVR AREA. BUT...H7-5 LYR HAS MSTND PER SPECIAL 18Z LWX RAOB.
THERE ALSO HAS BEEN A LTL WARMING IN THE H9-5 LYR...BUT THE XTREME
AT H8 ABT THE SAME /BTWN -1 TO -2 C/. THIS WARM AIR INTRUSION A
CONCERN TWD PTYPE.

NAM HAS INITIALIZED VERY POORLY...SPCLY H8 TEMPS ACRS
GRTLKS/MIDWEST/MID ALTC. AS A RESULT...IT DOES NOT LOOK LIKE THE
MASS FIELDS ARE IN STEP W/ THE DERIVED ONES. THRFR...CONFIDENCE IN
THE NAM SOLN LOW. GFS NOT THE BEST EITHER...BUT AT LEAST IT HAS
RUN-TO-RUN CONSISTENCY...AND A HISTORY OF BETTER PERFORMANCE FOR
WINTER STORMS. SO...FCST WAS WEIGHTED TWD GFS.

NRN AND SRN STREAMS REMAIN UNPHASED AS THE PASS THE CWFA BY
MIDNGT-DAWN. ENERGY TRANSFERS TO THE COAST FRI MRNG 12-15Z...AND
THEN CSTL STORM DEEPENS...DRAWS COLD AIR DOWN...AND RACES TWD NEW
ENGLND CSTL WATERS. AM CONCERNED ABT PCPN AMTS AS THIS TRANSFER
OCCURS. BASED UPON TRACK...ITS PSBL THAT SRN STREAM MSTR /OF WHICH
THERE IS PLENTY/ WL SLIDE BY SE OF CWFA...AND THEN NRN STREAM VORT
WL SWING THRU NXT...FOR ANTHR CPL INCHES OF SNW.

X-SCTNS DEPICT AN ENVIRONMENT FVRBL FOR SNW BURST...W/ LLVL
FRONTOGENETICAL FORCING...VERY STRONG UVV...AND EPV. DENDRITIC
SIGNAL NOT IDEAL...AS MAX UVV MISSING FAVORED TEMP RANGE. YET...
INDICATORS PRESENT FOR SNW.

NOW...FOR THE TROUBLING PART. GFS MDL PROFILES DEPICT AN INTRUSION
OF WARMER AIR ON A 40-50 KT LLJ. /ITS ON NAM TOO...STRNGR./  EVEN
THO EPV THERE...AND EVAP COOLING SHUD CHILL COLUMN...PLUS TIMING OF
EVENT /DIURNAL MIN/ SUPPORTS SNW AS WELL...CANNOT NEGLECT IMPACT OF
WARM NOSE...CONSIDERING ITS ALREADY PRESENT ON SNDGS...ONLY A DEGREE
OR TWO BELOW FRZG. GFS...PER ENERGY TECHNIQUE...SUGGESTS FZRA FOR DC
AND EVEN BWI. WL STAY COOLER THAN THIS SOLN...TILTING BALANCE TWD
SNW...BUT KEEPING A CHG TO MIX SNPL/FZRA AFT MIDNGT. THINK MOST PCPN
SHUD BE SNW...BUT THIS CERTAINLY A PART OF THE FCST THATS SUBJECT TO
CHG...W/ BIG CONSEQUENCES. WENT PRETTY CLOSE TO A 10 TO 1...BUT PL
OR FZRA CUD CHG THAT.

ONCE LOW DEPARTS...IT WL DEEPEN-- QUICKLY. EFFECT WL BE TO KICK UP
WINDS. AGN...BASED ON HRLY PROFILES...SHUD EASILY BE 30 KT OF WND TO
MIX DWN OVR LAND W/IN LWST 2K FT. IF SKIES WERE TO CLR /AND ON NW
WNDS CANT BE DISCOUNTED/...CUD SEE UP TO 40 KT OF MIXING. WENT ON
THE CONSERVATIVE SIDE. DUE TO LIQUID CONTENT OF SNW...DONT THINK
BLOWING/DRIFTING WL BE A BIG PRBLM.

STUCK CLOSE TO MAV FOR TEMPS DUE TO FVRD GFS SOLN. HWVR...UNDERCUT
MAXT BE A CPL. THIS BROUGHT MANY SITES ABV FRZG FOR MAXT TMRW. ANTHR
SLICE DWNWD MAY BE IN ORDER.

MARINE...W/ 40KT OF WND AVBL FOR MIXING 2000-3000FT IN WAKE OF CSTL
LOW TMRW AFTN...AND CAA FVRBL FOR DWNWD TRANSPORT...RAISED GLW FOR
THE AFTN HRS. SCA WL PRECEDE GALES.

AVIATION...
GFS HAS BEEN FAIRLY CONSISTENT IN DEVELOPING A SFC LOW OVER THE
SOUTHEAST STATES TONIGHT AND FORECASTING A NORTHEAST TRACK TO THE
DELMARVA PENINSULA BY 12Z FRIDAY BEFORE MOVING IT OFF THE COAST
FRIDAY MORNING. PREFER THE GFS SOLUTION OVER THE NAM WHICH SHOWS A
TRACK FURTHER WEST. CONSEQUENTLY...EXPECT PRIMARILY A SNOW EVENT AT
ALL TAF SITES...HOWEVER H85/H7 THICKNESSES SUGGEST MIXING WITH SLEET
AT DCA AND CHO FROM 06Z TO 14Z. EXPECT IFR CIGS/VSBYS AT MRB/CHO BY
06Z...AT IAD BY 07Z AND DCA/BWI/MTN BY 08Z AS SNOWFALL INTENSITY
INCREASES. INCLUDED TEMPO GROUPS FOR VLIFR CONDITIONS IN HEAVY SNOW
FROM 06Z-11Z AT MRB/CHO AND 08Z-13Z IAD/DCA/BWI/MTN. AS SFC LOW
MOVES AWAY TO THE NORTHEAST FRIDAY MORNING EXPECT RAPID IMPROVEMENT
TO MVFR CIGS AND VFR VSBYS AFTER 14Z AT CHO/MRB AND 17Z AT
DCA/BWI/MTN. NW WINDS BEHIND THE SYSTEM WILL RANGE FROM 10 TO 20 KT
AFTER 14Z WEST AND 17Z EAST WITH GUSTS TO 30 KT POSSIBLE AFTER 18Z.

LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)...
SYNOPSIS...MODEL CONSENSUS BEGINS TO WANE THIS WEEKEND BEHIND THE
CURRENT PROSPECTIVE WINTER STORM. EXPECT A TROUGH TO BUILD INTO THE
GREAT LAKES LATE THIS WEEKEND...SWINGING NORTH OF THE AREA. THIS
SHOULD TURN ON THE UPSLOPE/LAKE EFFECT MECHANISM FOR THE WESTERN
MOUNTAINS.

FORECAST RATIONALE...AS WITH MANY WINTER STORMS...MODELS ARE
EXHIBITING DIFFICULTY IN THE POST STORM PATTERN EVOLUTION. GFS
ENSEMBLES DID SHOW GOOD INTERNAL CERTAINTY WITH DEVELOPING A GREAT
LAKES TROUGH SUNDAY...WHICH PASSES TO OUR NORTH EARLY NEXT WEEK.
THEREFORE...HAVE AN EXTENDED PERIOD OF POSSIBLE UPSLOPE/LAKE EFFECT
SNOW SHOWERS IN THE WESTERN MOUNTAINS.

MEX FORECAST TEMPERATURES IN THE EXTENDED HAVE COME DOWN FROM NEAR
CLIMATOLOGY (NEAR 00Z GFS ENSEMBLE MOS) INTO THE 30S. THIS INDICATES
A PERSISTENT COLD DECEMBER PATTERN...AND HAVE REFLECTED THESE
CHANGES IN A DOWNWARD TREND OF FORECAST HIGH TEMPERATURES IN THE
EXTENDED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER STORM WARNING FOR DCZ001 FROM 6 PM THURSDAY TO NOON
     FRIDAY.
MD...HEAVY SNOW WARNING FOR MDZ002-003 FROM 6 PM THURSDAY TO NOON
     FRIDAY.
  ...WINTER STORM WARNING FOR MDZ004>007-009>011-013-014 FROM 6 PM
     THURSDAY TO NOON FRIDAY.
  ...WINTER WEATHER ADVISORY FOR MDZ016>018 FROM 6 PM THURSDAY TO
     NOON FRIDAY.
VA...WINTER STORM WARNING FOR VAZ021-025>027-029-030-036>042-
     050>054 FROM 6 PM THURSDAY TO NOON FRIDAY.
  ...HEAVY SNOW WARNING FOR VAZ028-031 FROM 6 PM THURSDAY TO NOON
     FRIDAY.
  ...WINTER WEATHER ADVISORY FOR VAZ055>057 FROM 6 PM THURSDAY TO
     NOON FRIDAY.
WV...HEAVY SNOW WARNING FOR WVZ048>053-055 FROM 6 PM THURSDAY TO
     NOON FRIDAY.
  ...WINTER STORM WARNING FOR WVZ054 FROM 6 PM THURSDAY TO NOON
     FRIDAY.
MARINE...GALE WARNING FOR ANZ530>537 FROM NOON FRIDAY TO 6 PM FRIDAY.
  ...SMALL CRAFT ADVISORY FOR ANZ530>537 FROM 1 AM FRIDAY TO NOON
     FRIDAY.
  ...SMALL CRAFT ADVISORY FOR ANZ530>537 FROM 6 PM FRIDAY TO 1 AM
     SATURDAY.

 &&

SHORT TERM...LISTEMAA

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
333 PM EST THU DEC 8 2005

ANZ530>537-DCZ001-MDZ002>007-009>011-013-014-016>018-VAZ021-
025>031-036>042-050>057-WVZ048>055-091100-
CHESAPEAKE BAY NORTH OF POOLES ISLAND MD-
CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT MD-
CHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH MD-
CHESAPEAKE BAY FROM NORTH BEACH TO DRUM POINT MD-
CHESAPEAKE BAY FROM DRUM POINT MD TO SMITH POINT VA-
TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD MD-
TIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND MD-
TIDAL POTOMAC FROM COBB ISLAND MD TO SMITH POINT VA-
DISTRICT OF COLUMBIA-ALLEGANY-WASHINGTON-FREDERICK MD-CARROLL-
NORTHERN BALTIMORE-HARFORD-MONTGOMERY-HOWARD-SOUTHERN BALTIMORE-
PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS-CALVERT-HIGHLAND-
AUGUSTA-ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-
NELSON-ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-FAUQUIER-LOUDOUN-
ORANGE-CULPEPER-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA-
KING GEORGE-GRANT-MINERAL-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-
PENDLETON-HARDY-
333 PM EST THU DEC 8 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MARYLAND WEST OF THE
EASTERN SHORE INCLUDING THE CHESAPEAKE BAY AND EAST OF GARRETT
COUNTY...EASTERN WEST VIRGINIA...NORTHERN AND CENTRAL VIRGINIA...
WASHINGTON DC AND THE TIDAL POTOMAC RIVER.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A WINTER STORM WARNING REMAINS IN EFFECT FOR MUCH OF THE AREA
THIS EVENING THROUGH EARLY FRIDAY. A HEAVY SNOW WARNING IS IN
EFFECT FOR THE POTOMAC HIGHLANDS AND WESTERN MARYLAND. A WINTER
WEATHER ADVISORY IS IN EFFECT FOR SOUTHERN MARYLAND AND THE
FREDERICKSBURG AREA.

SNOW IS EXPECTED TO BEGIN THIS EVENING AND CONTINUE INTO FRIDAY
MORNING. SLEET IS EXPECTED TO MIX WITH SNOW MAINLY EAST OF THE
BLUE RIDGE. SOME FREEZING RAIN IS ALSO POSSIBLE MAINLY ALONG AND
EAST OF THE INTERSTATE 95 CORRIDOR.

4 TO 8 INCHES OF SNOW IS EXPECTED WEST OF THE BLUE RIDGE. 3 TO 6
INCHES IS EXPECTED IN THE REMAINDER OF THE WARNING AREA INCLUDING
THE BALTIMORE AND WASHINGTON METROPOLITAN AREAS. OVER THE ADVISORY
AREA 2 TO 4 INCHES OF SNOW AND SLEET IS EXPECTED AT THIS TIME.

PLEASE REFER TO WBCWSWLWX (WWUS41) FOR FURTHER DETAILS.

A SMALL CRAFT ADVISORY IS IN EFFECT TONIGHT FOR THE TIDAL POTOMAC
AND CHESAPEAKE BAY.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THE WINTER STORM IMPACTING THE REGION TONIGHT WILL CONTINUE INTO
FRIDAY MORNING. ONCE PRECIPITATION COMES TO AN END FRIDAY
MORNING...STRONG NORTHWEST WINDS BETWEEN 15 AND 25 MPH WILL BE
POSSIBLE WITH GUSTS TO AROUND 35 TO 40 MPH.

PLEASE REFER TO WBCWSWLWX (WWUS41) FOR FURTHER DETAILS ON THE
WINTER STORM.

A GALE WARNING IS IN EFFECT FOR THE CHESAPEAKE BAY AND TIDAL
POTOMAC FOR FRIDAY AFTERNOON. A SMALL CRAFT ADVISORY WILL CONTINUE
THROUGH FRIDAY EVENING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER NETS WILL LIKELY BE ACTIVATED LATE THIS EVENING AND AGAIN
EARLY FRIDAY MORNING. SPOTTERS ARE ENCOURAGED TO RELAY THEIR
SNOWFALL REPORTS TO THE NATIONAL WEATHER SERVICE.

MANNING/ROGOWSKI