Special Weather Statement, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
802 PM EDT SAT AUG 6 2011

.SYNOPSIS...
A TROUGH OF LOW PRESSURE WILL ADVANCE ACROSS THE AREA OVERNIGHT. A
SERIES OF WEAK DISTURBANCES AND WEAK COLD FRONTS WILL PASS THROUGH
THE REGION DURING THE FIRST HALF OF THE NEW WORK WEEK...WITH HIGH
PRESSURE BUILDING IN BY LATE WEEK.

&&

.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
RADAR SCOPE STILL DOTTED WITH SHOWERS....AND SEVERAL TSTMS. THERE
APPEAR TO BE A COUPLE DIFFERENT LARGER-SCALE BOUNDARIES...
ESPECIALLY ONE THAT AT 8 PM EXTENDED FROM FDK TO NEAR IAD TO JUST
EAST OF CHO. THE BULK OF THE ACTIVITY IS ALONG AND EAST OF THIS
LINE...AND GRADUALLY PIVOTING EASTWARD.

MODELS ARE NOT PARTICULARLY EXCITED ABOUT RAIN CHANCES BEHIND THE
CURRENT ACTIVITY...AND QUITE A DECENT BREAK EXISTS ON RADAR
BETWEEN THE BLUE RIDGE AND THE OH/WV BORDER. HAVE THEREFORE
SUBSTANTIALLY LOWERED POPS FOR THE EVENING...DOWN TO 20S AND 30S
IN MANY AREAS WEST OF THE BLUE RIDGE. SOME OF THE ACTIVITY TO THE
WEST MAY MAKE ITS WAY INTO THE NRN SECTIONS OVERNIGHT...SO I DO
RETAIN HIGHER POPS IN THE NORTH AND ALONG THE WRN FRONT AFTER
06Z.

I TWEAKED OVERNIGHT LOWS UPWARD A BIT WITH THE 730 PM UPDATE AND
MAY HAVE TO GO EVEN A BIT HIGHER BY/BEFORE THE 1030 PM UPDATE.
DEWPOINTS ARE IN THE LOW/MID 70S AND THERE SHOULD NOT BE MUCH
REASON FOR THEM TO DROP A LOT OVERNIGHT. ALSO UNDER CONSIDERATION
FOR THE 1030 PM UPDATE IS THE ADDITION OF PATCHY FOG IN THE GRIDS
WEST OF THE CITIES. IT IS LIKELY TO OCCUR...JUST UNCERTAIN HOW
WIDESPREAD/DENSE.

&&

.SHORT TERM /7 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
WHILE WE SURE WOULD LK MORE RAIN I'M NOT SURE THIS SYSTEM WL BE
ABLE TO PROVIDE MUCH ON SUNDAY. SHORT WV WL BE EXITING INTO NEW
ENGLAND SUN MRNG...AND TAKING THE BEST CHCS OF PCPN W/ IT. THERE
WL STILL BE PLENTY OF LOW LVL MOISTURE...W/ DWPTS IN THE L70S...
AND W/ DCRSG AFTN CLD CVR HTG COULD CAUSE SCT RW/TRW TO DVLP.

IT'S BEEN VERY HOT FOR THE PAST FEW WEEKS...AND THE FACT THE TDA'S
TEMPS HV BEEN ABLE TO MAKE IN INTO THE U80S DESPITE NEAR OVC CLDS
IS TESTAMENT TO THAT. GIVEN WE EXPECT SOME SUNSHINE TMRW AFTN
TEMPS SHOULD ONCE AGN BE ABLE TO CLIMB INTO THE LM90S.

HEAT INDEX VALUES - THIS MAY TURN OUT TO THE BE THE MAIN CONCERN
FOR SUNDAY. W/ HIGH DWPTS HEAT INDEX VALUES WL APRCH 105 DURG THE
AFTN. THIS WL BE MENTIONED IN THE HWO AND A HEAT ADVSRY MAY BE IN
THE ERN PART OF THE FCST AREA SUN AFTN. LATER SHIFTS CAN EVALUATE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
SUN NGT THRU WED PD DOMINATED BY NWLY FLOW AND HINGES ON
TIMING/PLACEMENT/STRENGTH OF SEVERAL SUBTLE SHRTWV TROFS THAT WILL
NEAR THE MID-ATLC DURG THIS PERIOD. FOR NOW HAVE LOW/MAINLY DIURNAL
TSTM CHCS. FIRST DISTURBANCE POISED TO PASS N OF AREA MON AFTN. LEE
TROF IN PLACE...BUT 15-25 KT WNW FLOW FROM SFC TO MLVLS WILL BRING
DRIER AIR INTO RGN. COMBINED WITH EFFECTS OF DWNSLPG...CVRG OF
CNVTCN XPCD TO BE LOW.

AFOREMENTIONED DWNSLPG FLOW MAY LEAD TO EXCEPTIONALLY WARM TEMPS MON
AFTN...WELL INTO 90S...AND DEPENDING ON HOW SUCCESSFUL DRIER AIR
ALOFT IS AT MIXG DOWN TO SFC...HEAT INDICES MAY RISE TO NEAR 105F E
OF BLUE RIDGE. THEREAFTER...MODEST CAA SHUD KEEP TEMPS CLOSER TO
SEASONAL NRMLS.

HIPRES BUILDS IN WED NGT THRU FRI...THUS NO POPS DURG THIS PD.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
CIGS/VISBY HAVE GENERALLY BEEN VFR EXCEPT IN THE HEAVIEST
SHRA/TSRA THIS AFTERNOON. MOST OF THAT HEAVY STUFF IS GONE...SO
STARTED THE TAFS OUT VFR WITH THE 00Z PACKAGE. DID INCLUDE IN A
LITTLE GUSTY WIND WITH THE BOUNDARY PASSAGE BETWEEN 00Z-02Z AT
IAD/DCA...AND MAY HAVE TO AMEND TO ADD IT TO BWI/MTN. LATER
TONIGHT...CIGS WILL LOWER TO 1.5-2KFT AND SOME FOG IS EXPECTED
MAINLY AT MRB/CHO/IAD AS WELL. VFR CONDITIONS ARE EXPECTED ON
SUNDAY. UNSURE ABOUT RAIN POTENTIAL SO FOR NOW JUST MENTIONED VCSH
AT ALL SITES AFTER 17Z.

VFR CONDS DOMINATE THRU MID-WEEK...THOUGH LOW PROBABILITY OF MAINLY
AFTN/EVE SHWRS/TSTMS AS WELL AS ERY MRNG FOG DURG THE PERIOD. NW
WINDS MAY BE GUSTY MON...OTHERWISE MAINLY LGT NW WINDS XPCD.

&&

.MARINE...
SCA SUSTAINED WINDS PERSIST ON THE BAY...AND HAVE BEEN PERIODIC ON
THE LWR TIDAL POTOMAC. EVEN HAVE HAD SOME DECENT /25-30 KT/ GUSTS.
LEAVING THE SCA AS IS. WINDS SHOULD SLACKEN LATE TONIGHT AND TURN
WRLY AND THEN NRLY DURING THE DAY TOMORROW. A FEW TSTMS ARE
POSSIBLE SUNDAY AFTERNOON.

NW WINDS XPCD TO BE JUST BELOW SCA THRESHOLD ON MON/MON NGT...THEN
LIGHTER FOR REST OF WEEK. SVRL DISTURBANCES WARRANT LOW POPS
MON-WED...OTHERWISE HIPRES DOMINATES.

&&

.TIDES/COASTAL FLOODING...
JUST ISSUED A COASTAL FLOOD ADVISORY FOR ANNAPOLIS THROUGH 3 AM
SUNDAY. HYDROGRAPH IS BASICALLY ON TRACK WITH THE SAME TIME
YESTERDAY AND FORECAST MODEL INFO ACTUALLY SHOWS POTENTIAL FOR A
LITTLE HIGHER LEVEL TONIGHT THAN LAST NIGHT AS SRLY FLOW PERSISTS.

NOT AS CERTAIN ABOUT COASTAL FLOOD AT ALEXANDRIA. THEY ARE AT LOW
TIDE RIGHT NOW...AND BASICALLY AT THE SAME LEVEL AS THE PAST TWO
LOW TIDES /UNLIKE ANNAPOLIS/. ASSUMING ANOMALIES STAY THE SAME...
IT IS GOING TO BE REALLY REALLY CLOSE. WILL NOT ISSUE AT THIS
TIME...BUT WILL BE KEEPING AN EYE ON IT FOR THE NEXT SEVERAL
HOURS.

THIS SHOULD BE THE LAST HIGH TIDE OF CONCERN...THE NEXT ONE EARLY
TOMORROW AFTERNOON IS THE LOWER OF THE TWO TIDES...AND WINDS ALSO
TURN WRLY ON SUNDAY...BECOMING UNFAVORABLE FOR COASTAL FLOOD
CONCERNS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT SUNDAY FOR ANZ531>534-
     537>543.

&&

SYNOPSIS...JE
NEAR TERM...JE
SHORT TERM...ABW
LONG TERM...SBK
AVIATION...JE/SBK
MARINE...JE/SBK
TIDES/COASTAL FLOODING...JE

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