FXUS61 KAKQ 230338
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
1038 PM EST TUE DEC 22 2009

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN WEDGED ALONG THE EAST COAST THROUGH
CHRISTMAS EVE. A WARM FRONT...ASSOCIATED WITH A STRONG LOW
PRESSURE OVER THE MID MISSISSIPPI RIVER VALLEY...WILL SWING
THROUGH THE MID ATLANTIC REGION CHRISTMAS DAY...AND WILL BE
FOLLOWED BY A COLD FRONT THAT WILL MOVE THROUGH THE AREA BY
SATURDAY MORNING. HIGH PRESSURE BUILDS BACK INTO THE REGION FROM
THE WEST SATURDAY AFTERNOON INTO EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
MUCH COLDER AIR...TO THE NORTHWEST OF THE AREA IS TRYING TO PUSH
SE BEHIND A DEVELOPING FRONTAL BOUNDARY...THAT IS JUST NORTH AND
WEST OF THE AREA. THERE IS LITTLE MOISTURE ALONG THIS
FRONT...EXPECT FOR SOME MID TO HIGH LEVEL CLOUDS THAT ARE ACROSS NRN
VA AND WRN MD. THE MODELS DO SHOW SOME OF THIS MOISTURE TO DROP
SOUTHWARD WITH THE BACK DOOR LIKE COLD FRONT. BUT THEY SHOULD BE
SCATTERED IN NATURE. SO HAVE ALLOWED FOR MOSTLY CLEAR TO PC
CONDITIONS OVERNIGHT INTO THE DAY ON WEDNESDAY. FOR LOWS
OVERNIGHT...RADIATIVE CONDITIONS ARE FAVORABLE...BUT WITH THE
HIGHER DEW POINTS IN PLACE...HAVE RAISE OVERNIGHT LOWS A FEW
DEGREES. 

&&

.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH FRIDAY/...
TOMORROW AND CHRISTMAS EVE WILL AGAIN BE CHARACTERIZED BY
CONTINUED SEASONABLY CHILLY CONDITIONS AS STRONG SURFACE HIGH
PRESSURE (~1040 MB) BECOMES CENTERED NORTH OF THE GREAT LAKES
WHILE RIDGE AND ASSOCIATED LOW LEVEL COLD AIR DAMMING REMAINS 
ENTRENCHED DOWN THE ATLANTIC SEABOARD. LLVL THICKNESS PATTERN
(1000-950 MB) SUPPORTS SIMILAR SFC TEMP PROJECTIONS WED AND THU
(PER LOCAL STUDY)...WITH INTERMITTENT MID/UPR LVL CLOUDINESS.
HIGHS BOTH DAYS GENERALLY FROM MID 30S N TO MID 40S S. LOWS THU
MORNING AGAIN NEAR 20 N/NW TO AROUND 30 S/SE.

THU NIGHT AND CHRISTMAS...NAM/GFS/SREF CONTINUE TO SHOW A QUICK SHOT
OF WAA/WARM FRONTAL LIFT PIVOTING THROUGH THE MID ATLC REGION AS
THE DEEPENING SFC LOW LIFTS EVER SO SLOWLY NORTHWARD THROUGH THE
MID MS VLY. ISENTROPIC ANALYSIS SHOWS DEEP (ALBEIT NARROW W-E)
ADIABATIC MOISTENING BTWN 12-00Z (MORESO 18Z FRI-06Z SAT OVER THE
LWR ERN SHORE). THICKNESS PROGS PER ALL THE MODELS SHOW 850-700 MB
THICKNESSES GETTING PLENTY WARM DURING THIS PERIOD (1560-1580 M)...
HOWEVER THE 1000-850 MB THICKNESSES HOVERING BTWN 1310-1320 M FRI
MORNING SUGGEST THE POTENTIAL FOR A PERIOD OF FREEZING RAIN (PSBLY
A LIGHT SLEET/FZRA MIX AT THE ONSET) CHRISTMAS MORNING OVER THE WRN
(PIEDMONT) PTNS OF THE FCST AREA. FCST MODEL SOUNDINGS IN FACT
SHOW THE LLVL CAD PROFILE BECOMING MORE SHALLOW WITH TIME AS THE
NEAR SFC WINDS VEER MORE E-SE.

HOWEVER...CLIMATOLOGY SUGGESTS THAT EVEN WITH MORE OR LESS
EASTERLY SFC FLOW (VS N/NE)...THE NEAR SFC DAMMING...AIDED BY IN-
SITU EFFECTS OF EVAP COOLING INITIALLY AND SOME ADDITIONAL COOLING
VIA THE SLIGHT OROGRAPHIC LIFT...BECOMES TOUGH TO DISLODGE WHEN
THE PARENT LOW REMAINS WELL W OF THE MID ATLC REGION. THEREFORE...
HAVE INCREASED THE PROBABILITIES OF A PERIOD OF FZRA CHRISTMAS
MORNING...THOUGH THE QUICK MOVING NATURE OF THE DYNAMICAL SUPPORT
(DEEPER MSTR) AND MARGINAL TEMPS (UPR 20S TO LWR 30S) SHOULD
PRECLUDE A SIGNIFICANT ICING EVENT. MORE TO COME AS THE EVENT
DRAWS NEAR...FOR NOW WILL CONTINUE TO HIGHLIGHT THE THREAT FOR
FREEZING RAIN IN THE HWO.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
CENTER OF VIGOROUS UPR LVL SYSTEM IMPACTING THE MIDWEST MID-LATE 
THIS WEEK WILL CONTINUE TO ROTATE OVER THE GRT LKS RGN INTO THE 
WKND. DRY SLOT FILTERS INTO THE AREA FROM THE SW AS ASSCD FRONTAL 
SYSTEM SLIDES OFFSHORE FRI NIGHT/ERLY SAT. LOOK FOR TEMPS TO FALL 
BLO NRML INTO ERLY NEXT WEEK AS ANOTHER SURGE OF COOLER AIR FILTERS 
INTO THE RGN WITH UPR LVL LOW. COULD SEE SOME SCT -SN/FLY'S OVER THE 
FAR N/NE MON NIGHT/TUE IF ANY LAKE EFFECT STREAMERS CAN BE 
ESTABLISHED OFF THE GRT LKS...BUT HELD OFF IN FCST FOR NOW.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
NO MAJOR CHANGES TO FCST AS HI PRES REMAINS IN CONTROL OVER
CENTRAL VA. MOSTLY CLEAR SKIES AND LIGHT AND VARIABLE WNDS WL
CONTINUE OVERNIGHT WITH HI CLDS MVG INTO THE RGN SAT WED MRNG.

NE WNDS WL DVLP THU AHEAD OF THE NEXT WEATHER SYSTEM. CIGS MAY
LWR TO MVFR THU WITH AREAS OF PCPN LIKELY TO DVLP LATE THU NIGHT
OR FRI. THIS SHOULD MAINLY BE IN THE FORM OF RAIN. WIDESPREAD MVFR
WITH PERIODS OF IFR CAN BE EXPECTED AT THE TAF SITES WITH THIS
SYSTEM. CONDS SHOULD BEGIN TO IMPROVE ON SAT AS THE LOW PULLS OFF
TO THE NE AND HI PRES BEGINS TO BLD INTO THE AREA FROM THE GULF
COAST STATES.

&&

.MARINE...
NW WINDS WILL PREVAIL FOR THE NEXT FEWS. ANOTHER WEAK CCA SURGE IS 
ANTICIPATED WED NIGHT/THU AM AND COULD SEE LOW END SCA CONDITIONS 
DURING THAT TIMEFRAME. E/NE WINDS DVLP AS THE DAY PROGRESSES THU 
AND INCREASING IN SPEEDS WITH THE NEXT SYSTEM LATER FRI INTO SAT 
WITH FLAGS OF SOME KIND ANTICIPATED.

&&

.EQUIPMENT...
DUE TO PHONE LINE PROBLEMS...ALL NOAA ALL HAZARDS/WEATHER RADIO 
TRANSMITTERS OPERATING OUT OF WFO WAKEFIELD VA ARE DOWN UNTIL 
FURTHER NOTICE.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BKH
NEAR TERM...ESS
SHORT TERM...BKH
LONG TERM...CCW
AVIATION...AM
MARINE...CCW
EQUIPMENT...