Dense Fog in Virginia, December 23, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
919 PM EST SAT DEC 22 2007

.SYNOPSIS...
EASTERLY FLOW WILL CONTINUE ACROSS THE MID ATLANTIC OVERNIGHT. A
STRONG COLD FRONT WILL MOVE FROM WEST TO EAST ACROSS THE REGION
SUNDAY AFTERNOON AND EVENING. HIGH PRESSURE WILL BUILD OVER THE
AREA EARLY NEXT WEEK. UNSETTLED CONDITIONS MAY RETURN LATE IN THE
WEEK.

&&

.NEAR TERM /UNTIL 8 AM SUNDAY MORNING/...
LLVLS REMAIN NEARLY SATURATED...AND XPCT DIURNAL COOLING TO YIELD
ZERO DEWPT DEPRESSIONS. COOL WEDGE FM HIPRES NEAR NOVA SCOTIA MORE
ENTRENCHED ACRS CWFA THAN MDLD...AND AM A BIT MORE SCEPTICAL TWD
VEERING WNDS OVNGT...DESPITE 00Z LWX SNDG...WHICH DEPCIT SE/SLY
WNDS JUST OFF THE SFC. LLVL MSTR SHUD BE REINFORCED AS H8-7 SLY JET
PICKS UP IN ADVC OF TMRWS CDFNT. WL THEREFORE LEAN TWD LOW CLDS
OVR FOG...THO LCL VSBY RESTRICTIONS A GOOD BET...SPCLY OVR RDGS.
WL KEEP CHC POPS ALNG/W OF BLURDG SINCE THATS THE AREA WHERE
OVERRUNNING STRONGEST. TO THE E...A LOT OF LLVL MSTR...BUT FORCING
NIL.

&&

.SHORT TERM /8 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
LOTSA LLVL MSTR TO START THE DAY. WMFNT WL STRUGGLE TO WORK N. THE
COOL...MOIST MARITIME LYR WL BE FAIRLY SHALLOW /ARND 1000 FT/...
BUT THE SUN DOESNT COME MUCH MORE INEFFECTIVE AS IT IS THIS TIME
OF YEAR. EVENTUALLY...CIGS WL LIFT FOR A NARROW COLD RAIN BAND.

CDFNT TIMING LOOKS TO BE IN THE 19Z-01Z TIMEFRAME W TO E. MODELS
SHOW OCCLUDED LOW PRESSURE OVER THE GREAT LAKES MOVING INTO
EASTERN CANADA. TRIPLE POINT (INTERSECTION OF OCCLUDED/COLD/WARM
FRONT) MAY RESIDE JUST NORTH OF THE MASON DIXON LINE SUNDAY...
ALLOWING A WARM FRONT TO MOVE THROUGH WHERE THERE IS A BRIEF WARM
SECTORING BEFORE THE COLD FRONTAL PASSAGE.

MODELS FORECAST A STRONG LOW LEVEL SOUTHERLY JET ABOUT 50 KT. THIS
JET WILL TRANSPORT A RIBBON OF HIGH MOISTURE CONTENT...WITH
PRECIPITABLE WATERS ABOUT 1.25 INCHES WHICH IS ABOVE 2 STANDARD
DEVIATIONS AT SITE IAD FOR THIS TIME OF THE YEAR. IN
ADDITION...BOTH THE GFS AND NAM MODELS INDICATE ENHANCED LARGE
SCALE ASCENT ASSOCIATED WITH A FAVORABLE QUADRANT OF A 120-140 KT
JET AT 300 MB. THEREFORE... EXPECT AN ORGANIZED AREA OF SHOWERS
WITH THE POTENTIAL FOR A HALF OF AN INCH TO INCH OF RAINFALL TO
MOVE ACROSS THE CWA.

HAVE ALSO CONTINUED ISOLATED THUNDERSTORMS FOR ENTIRE CWA. NAM AND
GFS BOTH DEVELOP WEAK MAGNITUDES OF SURFACE BASED CAPE EAST OF THE
MTNS... WHICH COMBINED WITH STRONG SHEAR PROFILES COULD PRODUCE
SEVERE WEATHER. 21Z SREF ALSO HAS LOW PROBABILITY OF SUBZERO LI/S
S OF DC NEAR 00Z. TOTAL TOTALS ALSO REMAIN HIGH...SPCLY FOR THE
SEASON. EVEN WITH NO INSTABILITY...BELIEVE THAT SHOWERS COULD
ORGANIZE INTO A LOW TOPPED LINEAR SQUALL LINE THAT WOULD TAP INTO
THE STRONG WINDS ALOFT AND TRANSFER THEM TO THE SURFACE. ITS ALSO
INTERESTING THAT HELICITY AND EHI VALUES ARE RATHER HIGH...SO WILL
HAVE TO WATCH FOR ANY LOW TOPPED SUPERCELLS AHEAD OF THE MAIN LINE
THAT IS EXPECTED TO FORM.

COLD FRONT WILL BE EAST OF THE BAY BETWEEN 03Z AND 06Z. WINDS WILL
TURN TO THE WEST AND CONTINUE TO BE GUSTY BEHIND THE FRONT.
&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
THERES DECENT AGREEMENT AMONG THE MODELS IN HIGH PRESSURE BUILDING
ACROSS THE MID ATLANTIC EARLY NEXT WEEK. HAVE REMOVED HIDDEN POPS IN
THE HIGHLANDS AND SHENANDOAH VALLEY ON TUESDAY WITH HIGH PRESSURE IN
CONTROL. CONFIDENCE DECREASES FOR THE REST OF THE WEEK. MODELS HAVE
BACKED OFF SOME ON MID WEEK CHANCES OF PRECIP. GFS AND ECMWF ALSO
DISPLAY TIMING DIFFERENCES. THE OVERALL FLAVOR IS FOR A SOMEWHAT
PROGRESSIVE AND AMPLIFIED PATTERN FOR MID TO LATE WEEK...WITH
INDIVIDUAL DISTURBANCES MOVING ACROSS THE NORTHEAST AND MID
ATLANTIC. THE BEST CHANCE OF PRECIP LOOKS TO BE WEDNESDAY NIGHT INTO
THURSDAY. IF IT PRECIPITATES...WINTRY PRECIP IS POSSIBLE WEDNESDAY
NIGHT BEFORE CHANGING TO RAIN ON THURSDAY. FRIDAY LOOKS DRY...THEN
THE WEEKEND HAS THE POTENTIAL TO BE ACTIVE...BUT THERES DISAGREEMENT
AS TO WHETHER IT WOULD BE SATURDAY OR SUNDAY. HAVE CONTINUED
HPC/ECMWF THINKING WITH BRING IN PRECIP ON SATURDAY.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
AT TAF ISSUANCE TIME...FEW BRKS /FINALLY/ IN LOW DECK...BUT THOSE
PROVED TO BE BE SHORT LIVED AS LGT ELY /MARINE/ FLOW CONTS ACRS
CWFA. LIKE LAST NGT...DONT THINK WNDS WL BE COMPLETELY CALM...SO
SUSPECT ST WL BE FAVORED OVR FG. HWVR...IF BRKS IN LOW CLD DECK
CAN SUFFICIENTLY SUSTAIN THEMSELVES...THAT WUD BE AN OPPORTUNITY
FOR FOG TO DVLP. CIGS WL LWR OVRNGT...W/ LIFR PREVALENT. W/ FEW
XCPTNS...WL BE KEEPING VSBYS AOA 2SM-- IN THE IFR CATEGORY. JUST
ABV MARITIME DECK...SLY LLVL JETMAX WL BE PICKING UP TO 30-35
KT...RSLTG IN WS CONDS. HV MADE APPROPRIATE COMMENTS IN TAFS.

WAS A BIT CAUTIOUS IN VEERING WNDS...KEEPING AN ELY COMPONENT A BIT
LONGER. THAT IN TURN WL KEEP IFR CIGS IN PLACE THRU MUCH OF MRNG.
CDFNT WL APPROACH BY END OF TAF PD /22-24 UTC/. QSTN WL BE IF WMFNT
CAN MAKE IT THRU AREA FIRST...TURNING WNDS SLY...AND BREAKING UP
LLVL CLDS. IF SO...THEN LOOK FOR BIG WND GUSTS /40-50 KT/ ALNG/AHD
OF CDFNT. RIGHT NOW... BANKING AGAINST IT...AND HV CONTD WS GROUPS
FOR 50-60 KT WNDS AT 2000 FT. ITS NOT COMPLETELY OUT OF THE QSTN TO
SEE ISOL LTNG/VCTS MIXING 2000 FT WNDS TO SFC... PREDOMINANTLY S/E
OF DCA AFT 19Z. RISK LESS THAN EVEN A PROB30...AND HV OPTED TO OMIT
FM TAF. BUT...HV MNTND HERE FOR PLANNING PURPOSES.

SOUTHERLY WINDS WILL SHIFT TO THE WEST BEHIND THE FRONT. HIGH
PRESSURE WILL BUILD ACROSS THE REGION EARLY NEXT WEEK.

&&

.MARINE...
E/NELY WNDS AOB 10 KT ATTM...AND SHUD REMAIN FAIRLY STDY OVNGT.
MARINE LYR WL INHIBIT MUCH VERT TRANSPORT...BUT SHUD BE ENUF
MIXING TO IMPEDE SIG FOG.

HIGH END SMALL CRAFT ADVISORY IS LIKELY SUNDAY AND SUNDAY
NIGHT...WITH SYNOPTIC WIND GUSTS OF 30 KT BY SUNDAY AFTERNOON AS THE
STABLE WEDGE ERODES. CONTEMPLATED A GALE WARNING. HOWEVER...BELIEVE
GUSTS AOA 35 KT WOULD BE MOST LIKELY FROM CONVECTION THAT MOVES
ACROSS THE WATERS SUNDAY EVENING. THIS WOULD BE A SHORT DURATION
EVENT COVERED BY SPECIAL MARINE WARNINGS. HIGH PRESSURE BUILDS OVER
THE WATERS EARLY NEXT WEEK...LEADING TO LESS WIND.

&&

.TIDES/COASTAL FLOODING...
TIDES STILL RUNNING A FOOT TO A FOOT AND A HALF ABOVE ASTRONOMICAL
PREDICTIONS. WITH A EAST FLOW PERSISTING UNDER A FULL MOON UNTIL
A COLD FRONT PASSES SUN EVENING...MINOR COASTAL FLOODING IS EXPECTED
AT TIMES OF HIGH TIDE...ESPECIALLY SUNDAY MORNING.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 9 AM SUNDAY TO 4 AM EST MONDAY FOR
     ANZ530>537.

&&

SYNOPSIS...PELOQUIN
NEAR TERM...HTS
SHORT TERM...PELOQUIN/HTS
LONG TERM...PELOQUIN
AVIATION...HTS/PELOQUIN
MARINE...HTS/PELOQUIN
TIDES/COASTAL FLOODING...ROGOWSKI/HTS

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1004 PM EST SAT DEC 22 2007

ANZ530>537-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057-
231000-
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-NORTHERN BALTIMORE-HARFORD-
SOUTHERN BALTIMORE-PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS-
CALVERT-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA-
KING GEORGE-
1004 PM EST SAT DEC 22 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE MARYLAND PORTION OF THE
CHESAPEAKE BAY...TIDAL POTOMAC RIVER...AND ADJACENT COUNTIES IN
CENTRAL MARYLAND AND NORTHERN VIRGINIA AS WELL AS THE DISTRICT OF
COLUMBIA.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

SHOWERS AND ISOLATED THUNDERSTORMS WILL ACCOMPANY A COLD FRONT
PASSAGE ON SUNDAY AFTERNOON AND EVENING. ANY THUNDERSTORM THAT
DEVELOPS WILL BE CAPABLE OF PRODUCING DAMAGING WIND GUSTS.

A SMALL CRAFT ADVISORY IS IN EFFECT FOR SUNDAY AND SUNDAY NIGHT
FOR THE MARINE AREAS. GUSTS UP TO 30 KT CAN BE EXPECTED.

WITH AN EAST TO SOUTHEAST FLOW AND FULL MOON...WATER LEVELS MAY
INCREASE TO 1 TO 2 FEET ABOVE NORMAL SUNDAY. THESE ANOMALIES MAY
LEAD TO MINOR TIDAL FLOODING IN AREAS ADJACENT TO THE TIDAL
POTOMAC AND CHESAPEAKE BAY DURING TIMES OF HIGH TIDE THROUGH
SUNDAY EVENING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED OVERNIGHT. HOWEVER...
ACTIVATION MAY BE REQUIRED SUNDAY AFTERNOON.

MDZ003>005-009-010-501-502-VAZ021-025>031-036>042-050-051-
WVZ050>055-501>504-231000-
WASHINGTON-FREDERICK MD-CARROLL-MONTGOMERY-HOWARD-
EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-HIGHLAND-
AUGUSTA-ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-
NELSON-ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-FAUQUIER-LOUDOUN-
ORANGE-CULPEPER-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-PENDLETON-
HARDY-WESTERN GRANT-EASTERN GRANT-WESTERN MINERAL-EASTERN MINERAL-
1004 PM EST SAT DEC 22 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN WEST VIRGINIA...
NORTHERN AND CENTRAL VIRGINIA...AND CENTRAL AND WESTERN MARYLAND
WITH THE EXCEPTION OF GARRETT COUNTY.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

SHOWERS AND ISOLATED THUNDERSTORMS WILL ACCOMPANY A COLD FRONT
PASSAGE ON SUNDAY AFTERNOON AND EVENING. ANY THUNDERSTORM THAT
DEVELOPS WILL BE CAPABLE OF PRODUCING DAMAGING WIND GUSTS...
MAINLY ALONG AND EAST OF THE BLUE RIDGE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. HOWEVER...
ACTIVATION MAY BE REQUIRED SUNDAY AFTERNOON.

HTS