Flash Flood Warning 103, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
304 PM EDT WED JUL 5 2006

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
ONE LAST DAY OF SVR WX GETTING UNDERWAY ACROSS THE LWX CWA. MORNING
IAD RAOB MODIFIED FOR A CONSERVATIVE 85/72 SURFACE CONDS YIELDS
AROUND 1300 J/KG OF MLCAPE WITH NO INHIBITION. DEEP LYR SHEAR
SUFFICIENT TO LEAD TO STORM ORGANIZATION AND SHORT LINES AND BOWING
SEGMENTS.

MAIN SVR RISK WOULD BE DAMAGING WINDS AND HAVE HIGHLIGHTED SUCH
IN THE ZONES. HAIL POTENTIAL PRETTY LOW OVERALL AS THERE IS NOT
MUCH DRY AIR AVAILABLE IN THE MID LEVELS DESPITE INCREASING LAPSE
RATES.

MUCH MORE MOIST SOUNDING OVERALL TODAY WITH PWAT VALUES AROUND 2
INCHES. THIS IS A CONCERN IN LOCAL AREAS WHERE HEAVY RAINFALL OVER
THE PAST COUPLE OF DAYS HAS DROPPED FFG VALUES PRETTY LOW. WILL
CONTINUE THE FFA FOR THE CURRENT AREA.

CDFNT SLOWLY SAGS SOUTH OVERNIGHT WITH NORTH WINDS DEVELOPING. PCPN
MAY LINGER BRIEFLY INTO THE MORNING TOMORROW OVER FAR SOUTHEAST
ZONES AND WL CARRY LOW POPS.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
OBSERVATIONS...
500MB NORTHERN HEMISPHERIC HEIGHT/ANOMALY PATTERN DURING THE PAST
5 DAYS INDICATES A RIDGE/TROUGH CONUS PATTERN BECAME
ZONAL...BEFORE TRANSITIONING BACK TO A RIDGE/TROUGH PATTERN. THE
FLOW ACROSS THE PACIFIC HAS BECOME INCREASINGLY BLOCKED. WATER
VAPOR SHOWS A STRONG UPPER LOW ACROSS QUEBEC IS LOWERING HEIGHTS
ACROSS THE GREAT LAKES REGION. AN UPPER LOW/RIDGE/UPPER LOW
PATTERN IS NEARLY STATIONARY FROM TEXAS EAST TO OFF THE FLORIDA
ATLANTIC COAST. 11Z SURFACE ANALYSIS PLACED A COLD FRONT FROM NEW
ENGLAND SOUTHWEST THROUGH CENTRAL PENNSYLVANIA AND SOUTHEAST OHIO
(WHERE THE BOUNDARY STALLS). A TROUGH IS NOTED IN THE LEE OF THE
APPALACHIANS.

MODELS...
THE 12Z NAM/GFS/CANADIAN/UKMET ALONG WITH THE 00Z ECMWF WERE
EXAMINED. EACH WAS SIMILAR WITH ITS SYNOPTIC DEPICTION...WITH THE
MAIN TROUGH AXIS MOVING ACROSS NEW ENGLAND LATE THIS WORK WEEK. THEY
INDICATE A PIECE OF THIS TROUGH IS LIKELY TO SHEAR SOUTH...WITH AN
UPPER LOW DEVELOPING ACROSS THE MID ATLANTIC THROUGH THE WEEKEND.
THIS UPPER LOW IS SHOWN TO WEAKEN AND LIFT NORTHEAST EARLY NEXT
WEEK...AS HEIGHTS ACROSS MUCH OF THE CONUS INCREASE.

ENSEMBLE DATA...
500MB HEIGHT GFS ENSEMBLE MEMBERS FROM 00Z INDICATE
GOOD CERTAINTY WITH PASSING A TROUGH AXIS ACROSS NEW ENGLAND
THURSDAY. THERE IS MORE CERTAINTY THAT A TROUGH DEVELOPS OFF THE
EAST COAST INTO THE WEEKEND. THERE IS GOOD CERTAINTY AMONGST THE
MEMBERS THAT THE HEIGHT GRADIENT LIFTS FURTHER NORTH INTO CANADA
NEXT WEEK...GENERALLY ALLOWING FOR RISING HEIGHTS ACROSS THE CONUS.
SEVERAL MEMBERS INDICATE A WAVE WILL PROPAGATE EAST UNDERNEATH THE
BUILDING HEIGHTS AND APPROACH FOR THE END OF THE FORECAST CYCLE.

ENSEMBLE GFS MOS FROM 00Z INDICATE MEAN HIGHS RISE FROM THE LOWER
80S LATE THIS WEEK...INTO THE MID 80S SATURDAY ONWARD. MEAN LOWS IN
THE UPPER 50S FRIDAY MORNING MORNING...RISE WELL INTO THE MID 60S BY
MONDAY MORNING. MEAN POPS RISE TO NEAR 20 POPS MONDAY ONWARD.

FORECAST RATIONALE...
AS OF NOW...KEPT THE FORECAST DRY SATURDAY. THERE COULD BE AN
OPPORTUNITY FOR LIGHT SHOWERS ASSOCIATED WITH THE UPPER LOW. ONCE
THE PLACEMENT OF THE UPPER LOW...ITS VORTICITY LOBES...AND PROXIMITY
TO THE FRONTAL ZONE AND MOISTURE PLUME CAN BE MORE CONFIDENTLY
ESTABLISHED...SHOWERS MAY HAVE TO PLACED IN THE FORECAST. HAVE
INCREASED SKY COVER TO REFLECT AMOUNT OF CUMULUS DEVELOPMENT
EXPECTED GIVEN WEAKENING DOWNSLOPE FLOW AND SATURATED SOILS.
WRF-NMM (NAM) TENDS TO BUILD TROUGHS IN TOO MUCH ACROSS THIS REGION.
FOLLOWED THE CANADIAN AND GFS DEPICTION OF THE UPPER LOW MORE
CLOSELY.

CONFIDENCE LATER IN THE EXTENDED IS NOT QUITE HIGH AS YESTERDAY.
SEVERAL MODELS INDICATE A WAVE MAY SNEAK UNDERNEATH THE MAIN
STEERING FLOW AS HEIGHTS RISE ACROSS THE CONUS. TIMING THIS WAVE IS
PROBLEMATIC...HAVE SLIGHT CHANCE TO CHANCE POPS PER HPC LATE DURING
THE FORECAST CYCLE.

&&

.AVIATION...
CD FNT TO THE N WL MOVE INTO THE RGN OVRNGT. THIS WL TRIGGER TSTMS
DURG THE LATE AFTN/EVE HRS. FOR NOW HV INCLUDED A TEMPO WIND GUST
GROUP TO 30 KT...HOWEVER THIS MAY NEED TO BE AMENDED UPWARD WHEN
STORMS DVLP. AFTRWRDS NW WINDS WL BRING IN DRIER AIR...THIS WL KEEP
DOWN THE FOG PTNL.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLASH FLOOD WATCH FOR DCZ001 UNTIL 8 AM THURSDAY.
MD...FLASH FLOOD WATCH FOR MDZ002>007-009>011-013-014-016>018 UNTIL
     8 AM THURSDAY.
VA...FLASH FLOOD WATCH FOR VAZ042-052>057 UNTIL 8 AM THURSDAY.
WV...FLASH FLOOD WATCH FOR WVZ051>053 UNTIL 8 AM THURSDAY.
MARINE...NONE.
&&

SHORT TERM...MANNING
LONG TERM...ROGOWSKI
AVIATION...ABW

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1140 AM EDT WED JUL 5 2006

ANZ530>537-DCZ001-MDZ002>007-009>011-013-014-016>018-VAZ021-
025>031-036>042-050>057-WVZ048>055-061015-
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-
1140 AM EDT WED JUL 5 2006

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...TODAY AND TONIGHT

A FEW SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS THE REGION THIS
AFTERNOON AND THIS EVENING. A COLD FRONT WILL SLOWLY PUSH SOUTH
ACROSS THE AREA AND PRODUCE SHOWERS AND THUNDERSTORMS OVER THE MID
ATLANTIC. ANY SEVERE THUNDERSTORMS THAT DEVELOP WILL HAVE THE
POTENTIAL TO PRODUCE DAMAGING WINDS AS WELL AS VERY HEAVY RAIN. THE
MOST LIKELY TIME FOR SEVERE WEATHER WILL BE BETWEEN 2 PM AND 8 PM.

RECENT RAINFALL HAS LEFT SOIL CONDITIONS SATURATED ACROSS THE
INTERSTATE 95 CORRIDOR...NORTHERN SHENANDOAH VALLEY AND SOUTHERN
MARYLAND. HEAVY RAINFALL FROM THUNDERSTORMS TODAY MAY LEAD TO FLASH
FLOODING OF SMALL CREEKS...STREAMS AND URBAN AREAS. A FLASH FLOOD
WATCH HAS BEEN ISSUED FOR A PORTION OF THE AREA THROUGH TONIGHT.
PLEASE REFER TO /WBCFFALWX/ FOR FURTHER DETAILS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED LATER TODAY.

MANNING

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
508 PM EDT WED JUL 05 2006

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0330 PM     FLASH FLOOD      WASHINGTON              38.91N 77.02W
07/05/2006                   DISTRICT OF COLUMB DC   AMATEUR RADIO

            HIGH WATER AT SOUTH CAPITOL STREET AND MARTIN LUTHER KING
            AVENUE IN SOUTHEAST DC. ROAD IMPASSABLE.

0345 PM     FLASH FLOOD      ARLINGTON               38.88N 77.10W
07/05/2006                   ARLINGTON          VA   BROADCAST MEDIA

            HIGH WATER REPORTED ON ROUTE 110 NORTH OF PENTAGON.

0415 PM     FLASH FLOOD      ANNANDALE               38.83N 77.21W
07/05/2006                   FAIRFAX            VA   LAW ENFORCEMENT

            PROSPERITY AVENUE AT LITTLE RIVER TURNPIKE CLOSED DUE TO
            HIGH WATER. WOODBURN AND SPICEWOOD ALSO FLOODED OUT.

&&

RDH

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