Severe Thunderstorm Warning 364, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
916 PM EDT THU OCT 18 2012

.SYNOPSIS...
A COLD FRONT WILL PUSH THROUGH THE MID ATLANTIC EARLY FRIDAY. AN
UPPER LEVEL TROUGH WILL THEN PERSIST ACROSS THE NORTHEASTERN
STATES THROUGH SATURDAY. HIGH PRESSURE WILL BUILD BACK ACROSS THE
REGION FROM THE WEST SATURDAY THROUGH MONDAY...AND CONTINUE WELL INTO
NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
CNVTCN FLARING UP LATE THIS EVE AS MAIN PRE-FRONTAL TROF PASSES
THRU HIGHLANDS. CLUSTERS OF SHWRS/TSTMS ALONG/AHEAD OF THIS
FEATURE...AS FAR EAST AS WRN DC/BALT METRO. 0Z SOUNDING HAS
IMPRESSIVE WIND FIELD...SO STRONGER CELLS MAY CONT GUSTY WINDS AND
EVEN DMGG DOWNBURSTS. IN ADDITION...0C AND -20C LVLS ARE VERY
LOW...AND HAIL IS A RISK. TIMING OF ACTIVITY HAS CONTINUALLY
SLOWED WITH SUCCESSIVE MESOSCALE GUIDANCE RUNS...SO POPS ADJUSTED
ACCORDINGLY. BEST CHC OF SVR WX WILL BE BEFORE ABOUT 2 AM EDT.
SHWRS LIKELY TO CONT WELL INTO THE NGT...GRADUALLY ENDING FROM W
TO E BEFORE SUNSET. WHEN PCPN WANES...SATURATED LOW/MID LVLS AND
DECOUPLG NEAR THE SFC WILL SUPPORT AT LEAST PATCHY FOG DVLPMNT.
PREV DISCUSSION FOLLOWS...

PRECIPITATION WILL LAG BEHIND THE BOUNDARY DURING AT LEAST THE FIRST
PART OF FRIDAY ESPECIALLY OVER EASTERN SECTIONS OF THE FORECAST
AREA. WILL KEEP CHANCES MUCH OF THE MORNING INTO THE AFTERNOON
HOURS. HIGH TEMPERATURES WILL STILL RISE ABOVE NORMAL DURING FRIDAY
BUT CONDITIONS WILL BE NOTICEABLY DRIER.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
SPRAWLING CLOSED LOW EJECTS NORTHEAST FROM THE CENTRAL GREAT LAKES
FRIDAY NIGHT...WITH AN UPR TROUGH PERSISTING ACROSS THE MID ATLANTIC
THROUGH SATURDAY. SFC HIGH PRESSURE SOUTH OF THE LOW...WILL BUILD
EAST INTO THE MID ATLANTIC THROUGH THIS TIME...LIMITING THE EXTENT
OF PRECIP TO THE POTOMAC HIGHLANDS AND NORTHWESTERN ZONES. ONE
EXCEPTION OCCURS AS THE TROF AXIS PUSHES EAST ACROSS THE MID ATLANTIC
SATURDAY AFTERNOON. COMBINATION OF PVA AND PEAK HEATING COULD
CAUSE SHOWERS INTO THE WRN BALT-WASH SUBURBS...WHERE SLIGHT CHANCE
POPS WERE INTRODUCED. TEMPERATURES RETURN TO NORMAL FOR THE
WEEKEND AS MID CONTINENTAL AIR BUILDS IN FROM THE WEST WITH THE
HIGH PRESSURE. MIN TEMPS FRIDAY NIGHT MID TO UPR 30S IN THE
POTOMAC HIGHLANDS...LOW TO MID 40S PIEDMONT AND WEST...LOW 50S
COASTAL PLAINS. MAX TEMPS SATURDAY LOW TO MID 60S WEST OF THE BLUE
RIDGE...MID TO UPR 60S EAST.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
SATURDAY NIGHT WELL INTO NEXT WEEK...A DOMINATING RIDGE BUILDS IN
THE WAKE OF THE GREAT LAKES LOW WITH A SFC HIGH PERSISTING ACROSS
THE E-CNTRL CONUS PERHAPS THROUGH NEXT WEEK /PER RECENT ECMWF RUNS/
OR PERHAPS SHUNTING TO THE SERN CONUS BY MID NEXT WEEK WITH A WEAK
COLD FRONT ENTERING THE MID ATLANTIC /PER RECENT GFS RUNS/. DRY AND
SEASONABLE SUNDAY THROUGH TUESDAY WITH A SLIGHT WARMING TREND...NO
FREEZES EXPECTED THROUGH NEXT WEEK. ONLY SLIGHT CHANCE POPS FOR THE
POTOMAC HIGHLANDS IN THE MIDWEEK FOR NOW.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
SHWRS/TSTMS ONGOING AT 1Z FOR MRB/IAD/CHO...AND WILL SPREAD INTO
RMNG TAF SITES BY 3Z. LOCALIZED STRONG WINDS PSBL WITH STRONGER
ACTIVITY...AND SPORADIC/SIGNIFICANT RESTRICTIONS LIKELY THRU 6Z.
THEREAFTER...GUIDANCE SUGGESTS FOG CUD SET IN...SO WENT IFR FOR
VSBYS AREAWIDE.

CONDITIONS WILL IMPROVE FROM WEST TO EAST MID TO LATE MORNING
FRIDAY OVER WESTERN AND CENTRAL SECTIONS AND DURING THE AFTERNOON
OVER THE EAST.

SWLY FLOW SHIFTS NWLY FRIDAY NIGHT BEHIND THE ACTUAL COLD FRONT. UPR
TROUGH KEEPS MID LEVEL CLOUDS AND POSSIBLE LIGHT RAIN NW OF
BALT-WASH /INCL KMRB/ SATURDAY AFTERNOON. HIGH PRESSURE AND VFR THEN
SATURDAY NIGHT WELL INTO NEXT WEEK. MORNING FOG CHANCES MONDAY AND
TUESDAY NIGHTS.

&&

.MARINE...
SMALL CRAFT CONDITIONS WILL CONTINUE TO RAMP UP FOR THE REMAINDER OF
THIS AFTERNOON AND EVENING WITH GUSTS APPROACHING 25 TO 30 KTS AT
TIMES. SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS WILL
CROSS THE WATERS LATER TONIGHT. SOME OF THESE STORMS COULD MIX DOWN
STRONGER GALE FORCE WIND GUSTS. WILL MONITOR THIS POTENTIAL
THROUGHOUT THIS EVENING.

COLD FRONT WILL CROSS THE WATERS OVERNIGHT INTO FRIDAY BUT SMALL
CRAFT CONDITIONS WILL BE POSSIBLE FRIDAY AFTERNOON INTO THE EARLY
EVENING.

SLY FLOW CONTINUES INTO FRIDAY EVENING BEFORE VEERING WLY. CONTINUED
SCA UNTIL 8PM FRIDAY. WLY FLOW BELOW SCA CRIT THEN SAT/SUN AS HIGH
PRESSURE BUILDS. HIGH PRESSURE OVERHEAD/TRANQUIL MONDAY THROUGH THE
MIDDLE OF NEXT WEEK.

&&

.TIDES/COASTAL FLOODING...
ANOMALIES AOA 1 FT ABV NRML ACRS POTOMAC SHORES...SO RAISED ADZY
FOR THESE LOCATIONS. PREV DISCUSSION FOLLOWS...

INCREASING SOUTHERLY FLOW AND CHANNELING AIDING IN POSITIVE TIDAL
ANOMALIES MAINLY OVER THE WESTERN CHESAPEAKE BAY. COASTAL FLOOD
ADVISORY HAS BEEN ISSUED FROM CALVERT NORTH TO HARFORD FOR TIDE
RISES ABOUT ONE FOOT ABOVE ASTRONOMICAL PREDICTION FOR THE NEXT
CYCLE. TIDES WILL RECEDE OVERNIGHT AS THE FRONT MOVES THROUGH.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY UNTIL 2 AM EDT FRIDAY FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 2 AM EDT FRIDAY FOR MDZ007-011-
     013-014-018.
VA...COASTAL FLOOD ADVISORY UNTIL 2 AM EDT FRIDAY FOR VAZ054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ530>534-
     536>543.
     SMALL CRAFT ADVISORY FROM NOON TO 6 PM EDT FRIDAY FOR
     ANZ530>532-535-536-538>540-542.
     SMALL CRAFT ADVISORY FROM NOON TO 8 PM EDT FRIDAY FOR ANZ533-
     534-537-541-543.
     SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ535.

&&

SYNOPSIS...BAJ/KONARIK
NEAR TERM...KONARIK/KRW
SHORT TERM...BAJ
LONG TERM...BAJ
AVIATION...BAJ/KONARIK/KRW
MARINE...BAJ/KONARIK/KRW
TIDES/COASTAL FLOODING...KONARIK/KRW

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1025 PM EDT THU OCT 18 2012

VAZ037>039-050-051-056-190300-
ORANGE VA-GREENE VA-CULPEPER VA-MADISON VA-ALBEMARLE VA-
SPOTSYLVANIA VA-
1025 PM EDT THU OCT 18 2012

...STRONG THUNDERSTORM TO AFFECT ORANGE...GREENE...CULPEPER...
MADISON...ALBEMARLE AND SPOTSYLVANIA COUNTIES...

AT 1025 PM EDT...A STRONG THUNDERSTORM WAS LOCATED 3 MILES SOUTH OF
BARBOURSVILLE...MOVING NORTHEAST AT 30 MPH.

LOCATIONS IMPACTED INCLUDE ORANGE.

STORM INTENSITY IS INCREASING...AND SEVERE WEATHER MAY DEVELOP
RAPIDLY. REMAIN ALERT...AND BE PREPARED TO TAKE ACTION IF WARNINGS
ARE ISSUED.

WIND GUSTS IN EXCESS OF 50 MPH AND SMALL HAIL CAN BE EXPECTED WITH
THIS STORM. WINDS THIS STRONG CAN BRING DOWN LARGE TREE BRANCHES.
TAKE SHELTER UNTIL THE STORM HAS PASSED.

&&

LAT...LON 3817 7841 3840 7798 3820 7783 3813 7801
      3813 7806 3815 7810 3813 7813 3812 7819
      3813 7821 3807 7824 3802 7830
TIME...MOT...LOC 0225Z 239DEG 25KT 3814 7825