FXUS61 KAKQ 262040
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
340 PM EST SAT DEC 26 2009
.SYNOPSIS...
LOW PRESSURE...OVER THE DELMARVA THIS AFTERNOON...WILL LIFT NORTHEAST OF
THE AREA TONIGHT. WEAK HIGH PRESSURE WILL BUILD OVER THE AREA
SUNDAY...THEN A COUPLE REINFORCING COLD FRONTS WILL MOVE ACROSS
SUNDAY NIGHT AND MONDAY NIGHT. STRONG HIGH PRESSURE WILL BUILD IN FROM
THE WEST TUESDAY THROUGH WEDNESDAY.
&&
.NEAR TERM /THROUGH SUNDAY/...
THE LARGE CLOSED LOW OVER THE MID WEST AND OHIO VALLEY FINALLY
HEADS EAST OVER THE NEXT 24 HOURS. BEFORE IT ARRIVES HOWEVER...A
STRONG DRY SLOT WILL BE SLIDING INTO THE AREA HEAD OF
IT...ALLOWING FOR CLEARING AND DRIER WEATHER. A WEAK SURFACE LOW
THAT HAS BEEN HANGING ALONG THE VIRGINIA AND DELMARVA COAST TODAY
WILL LIFT NE THIS EVENING...TAKING ANY LINGERING SHOWERS WITH IT.
THE DRY SLOT WILL SPREAD ACROSS THE AREA...KILLING ANY RAIN
CHANCES...BUT UNTIL THE FLOW INCREASES OUT OF THE WEST...THE LOW
LEVEL MOISTURE WILL REMAIN TRAPPED WITH LOW STRATUS LINGERING INTO
THE EVENING HOURS. ONCE THE FLOW PICKS UP OUT OF THE WEST...SHOULD
SEE THE CLOUDS BEGIN TO CLEAR WITH DRIER AIR...AND LOWER DEW
POINTS ARRIVING. HAVE LEAN TOWARD THE COOLER MET NUMBERS TONIGHT
WITH THE ANTICIPATED CLEARING...BUT SHOULD THE CLOUDS HOLD...LOWS
WILL STAY UP HIGHER.
ON SUNDAY WITH THE WEST FLOW AND DRIER AIR...SHOULD SEE A LOT OF
SUNSHINE AND TEMPERATURES WILL STILL BE MILD. GUIDANCE HAS A GOOD
SPREAD...BUT BASED UPON THE 850 MB TEMP...HAVE GENERALLY BLENDED
THE NUMBERS IN THE LOW TO MID 50S IN MOST AREAS.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
THE UPPER TROUGH FINALLY SWINGS INTO THE EASTERN US SUNDAY NIGHT
AND TURNS THE FLOW NW FOR MONDAY AND TUESDAY. THERE ARE SEVERAL
SHORTWAVES ROTATING AROUND THE TROUGH...WHICH WILL PUSH A COUPLE
REINFORCING COLD FRONTS THROUGH THE AREA. THE TRACK OF THE
SHORTWAVES HOWEVER WILL BE NORTH OF THE REGION...SO NOT
ANTICIPATING ANY PCPN WITH THE FRONT...BUT WILL SEE MUCH COLDER
AIR PUSHING INTO THE AREA. HIGH PRESSURE THEN BUILDS INTO THE AREA
ON TUESDAY AS STRONG CANADIAN HIGH PRESSURE SETTLES INTO THE
EASTERN HALF OF THE COUNTRY. OVERALL SHOULD SEE DRY WEATHER AND
FEW CLOUDS THROUGH THE PERIOD...EXPECT ALONG AND NEAR THE COLD
FRONTAL PASSAGES. FOR TEMPERATURES...WILL SEE A COOLING TREND WITH
THE COLD AIR ADVECTION. HAVE LOWERED VALUES INTO THE UPPER 30S TO
LOWER 40S ON TUESDAY...AND IT COULD BE COOLER IF THE -10C 850 AIR
VERIFIES.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
HIGH PRESSURE AND DRIER AIR REMAINS OVER THE FORECAST AREA AT THE
ONSET. ECMWF HAS A COUPLE OF VORT MAXES SWINGING ACRS THE REGION
LATE WEDNESDAY AND THURSDAY. IN GOING WITH THE TRENDS...CAN XPCT AND
INCREASE IN CLOUDS BEGINNING LATE ON WEDNESDAY. AS NEXT SYSTEM
APPROACHES WL CONTINUE WITH AN INCREASED CHANCE OF PRECIPITATION
INTO THURSDAY. MODEL FORECAST MAX TEMPS WL BE COOL
THROUGHOUT...GENERALLY IN THE 40S AND MODEL 850MB LOWS ARE PROGGED
TO BE NEAR THE FREEZING MARK FOR PORTIONS OF THE AREA. THIS RAISES
THE QUESTION FOR SOME FROZEN PRECIP CHANCES EARLY THURSDAY BUT DUE
TO UNCERTAINTIES IN LATE DAY 5 THRU 7...HAVE CHOSEN TO KEEP AS ALL
LIQUID FOR NOW.
&&
.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
WIDESPREAD IFR CIGS CONT OVER ALL OF THE TAF AREA...SAT SHOWS
DRIER AIR PUSHING IN WEST OF RIC BUT TIMING REMAINS THE FCST
PROBLEM. XPCT MVFR CONDS TO START ARND 21Z AND LINGER THRU THE
EVE HRS. DRIER NW FLOW MOSE IN BY ERLY AM BUT FCST SOUNDINGS SHOW
LOW LVL COULD LAST LONGER AT RIC/SBY. ALL SITES VFR BY LATE AM. CONT
VFR INTO MID WEEK AS WEAK HIGH PRES BUILDS IN FROM THE SW
SUNDAY...WITH STRONGER HIGH BUILDING IN FROM THE WNW MON THROUGH
WED.
&&
.MARINE...
AS LOW PRESSURE CURRENTLY CENTERED OVER THE REGION PUSHES OFF TO THE
NORTHEAST....CAN EXPECT PRESSURE GRADIENT TO RELAX SOMEWHAT INTO
THE EVENING HOURS. HOWEVER THE BIGGEST ISSUE FOR THE REMAINDER OF
THE WEEKEND INTO THE FIRST PART OF THE WORK WEEK HAS TO DO WITH
SWELL. RIGHT NOW....SEAS ARE RUNNING HIGHER THAN WHAT WAS PREVIOUSLY
FORECAST SO IN THE NEAR TERM WL HAVE TO MAKE SOME ADJUSTMENTS
THERE. AT ANY RATE...CURRENT RAISED FLAGS LOOK GOOD FOR NOW WITH THE
SWELL FACTOR AND SUBSEQUENT WINDS INCRS POSSIBLE SOMETIME BETWEEN
LATE SUNDAY INTO EARLY MONDAY. IN THE CHES BAY...SHUD BE ABLE TO
LOWER FLAGS AFTER 7 PM PARTICULARLY FOR THE MOUTH OF THE BAY AS SEAS
LOWER BELOW 4 FEET THERE.
&&
.HYDROLOGY...
THE COMBINATION OF THE FACTORS OF RAINFALL SATURDAY GENERALLY IN THE
ONE TO ONE AND A HALF INCH RANGE...MELTING SNOW PACK ACROSS THE
UPPER AND LOWER RIVER BASINS AND SATURATED SOILS HAS INCREASED
RUNOFF AND FLOOD POTENTIAL OVERALL. AS A RESULT...SHARP RISES HAVE
BEEN OBSERVED ALONG AREA RIVERS AND STREAMS. THROUGHOUT THE REMAINDER
OF THE WEEKEND INTO THE FIRST PART OF THE WEEK...MOST RIVERS WILL
REMAIN BETWEEN THREE-QUARTERS AND BANKFULL...MAYBE GETING TO HALF
BANKFULL TOWARDS THE END OF THE WEEK. A RIVER FLOOD WARNING HAS
ALREADY BEEN ISSUED FOR THE MEHERRIN RIVER NEAR LAWRENCEVILLE FOR
MINOR FLOODING. THE JAMES RIVER IN THE RICHMOND VICINITY MAY HAVE TO
BE WARNED FOR MINOR FLOODING LATER THIS AFTERNOON. OTHER SLOWER
RESPONSE RIVERS IN THE CHOWAN BASIN MAY NEED WARNINGS LATER IN THE
NEXT WEEK.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...COASTAL FLOOD ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
MDZ021-023.
NC...NONE.
VA...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ632.
SMALL CRAFT ADVISORY UNTIL 4 PM EST MONDAY FOR ANZ650-652-654-
656-658.
&&
$$
SYNOPSIS...ESS
NEAR TERM...ESS
SHORT TERM...ESS
LONG TERM...KLL
AVIATION...CY
MARINE...KLL
HYDROLOGY...
