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Area Forecast Discussion

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FXUS61 KLWX 151419
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1019 AM EDT TUE APR 15 2014

.SYNOPSIS...
A STRONG COLD FRONT WILL MOVE THROUGH THE MID-ATLANTIC REGION TODAY.
ARCTIC HIGH PRESSURE BUILDS INTO THE REGION TONIGHT AND WEDNESDAY.
THE CENTER OF THE HIGH SHIFTS NORTHEAST INTO NEW ENGLAND BUT
CONTINUES TO RIDGE SOUTHWARD INTO THE MID-ATLANTIC REGION LATE IN
THE WEEK.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...

STRONG COLD FRONT PASSING OVER OUR WESTERN COUNTIES IN THE
MOUNTAINS AT 10AM IS CAUSING A FEW THREATS TO DEAL WITH...

FIRST IS ENOUGH WIND SHEAR IN THE LOW LEVELS TO CAUSE SOME
ROTATING SEGMENTS IN LOWER S MD DURING THE MID TO LATE MORNING.
THERE IS A ISOLATED THREAT OF DAMAGING WINDS WITH THESE AS THEY
MOVE EAST. RADAR TEAM IS MONITORING. THING LIMITING THIS IS THE
LOW LEVEL STABILITY IN THE BOUNDARY LAYER AND THE VERY LIMITED
AMOUNT OF INSTAB OVER THAT.

SECOND IS ISOLATED FLOODING THREAT. THE ENHANCED AREAS ON RADAR
OVER THE ADJACENT BAY COUNTIES AND BALTIMORE AT 10AM ARE PRODUCING
A HALF INCH TO INCH OF RAIN IN ABOUT AN HOUR AS THEY PASS BY. AT
THIS TIME BASED ON 1 HR AND 3 HR FLASH FLOOD GUIDANCE...THINK
GENERALLY THE RAIN WILL BE ABSORBED BY THE SPRING GROUND AND
EMERGING VEGETATION. HOWEVER SOME ISOLATED AREAS OF LOCALIZED
FLOODING ARE POSSIBLE LATE THIS MORNING IN THESE COUNTIES AND
BALTIMORE.

THIRD IS COLD AIR COMING IN WITH PRECIP AROUND. LATEST MESO MODEL
GUIDANCE HAS SNOW CHANGEOVER IN THE POTOMAC HIGHLANDS IN OUR
HIGHEST SPOTS OUT WEST CHANGING OVER IN THE EARLY AFTERNOON. OTHER
THREAT OF CHANGEOVER AND SOME LIGHT ACCUMS ON THE BLUE RIDGE AND N
CENTRAL MD HIGHLANDS ISNT EXPECTED UNTIL EVENING JUST BEFORE THE
PRECIP KICKS OUT. AT THIS POINT NOT EXPECTING SNOWFLAKES OVER THE
METRO AREA...BUT SOME WET NON ACCUM FLAKES POSSIBLE AT THE END.

EXPECT THE MORNING LINE OF HEAVY PRECIP OVER THE BAY COUNTIES TO
KICK EAST DURING THE LATE MORNING. THAT SHOULD LEAVE A FEW HOURS
OF SCT SHOWERS BEFORE ANOTHER SHIELD OF PRECIP DEVELOPS OVER THE
AREA EARLY THIS AFTERNOON WHICH WILL LAST THE REST OF THE DAY.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...

A SIGNIFICANT PRESSURE SURGE TO ACCOMPANY THE STRONG CAA WILL 
PRODUCE GUSTY WINDS BEHIND THE FRONT. CONSIDERED A WIND ADVISORY... 
PARTICULARLY FOR THE HIGHER ELEVATION RIDGES BUT WINDS AT THE TOP OF 
THE MIXING LAYER ONLY MARGINALLY SUPPORTIVE OF ADVISORY LVL WIND 
GUSTS. THE STRONGEST WINDS WILL OCCUR IN THE ERY EVE...ALLOWING THE 
DAY SHIFT TO LOOK THRU THE LATEST TRENDS IN OBS AND NEAR-TERM 
GUIDANCE.

MIN TEMPS TNGT AOB FREEZING FOR THE ENTIRE CWA EXCEPT IN THE CITIES 
AND ALONG THE WRN SHORE OF THE CHSPK BAY. FREEZE WARNINGS ISSUED
FOR COUNTIES EAST OF THE BLUE RIDGE...WHERE THE GROWING SEASON HAS
ALREADY BEGUN.


WEDNESDAY...HIGH PRESSURE BUILDS NORTHEAST ACROSS THE NRN 
MID-ATLANTIC...BECOMING A 1045 MB OR SO SFC HIGH OVER NEW ENGLAND
WEDNESDAY NIGHT. MAX TEMPS AROUND 50F ARE 15 OR SO DEGREES BELOW
NORMAL. SUNNY WITH PERHAPS SOME WISPY CIRRUS IN THE AFTERNOON
OVERRUNNING A LOW AMPLITUDE RIDGE TO OUR WEST. STRONG NWLY GUSTS
IN THE MORNING EASE THROUGH MIDDAY. PARTIAL DECOUPLING WEDNESDAY
NIGHT WITH MIN TEMPS AROUND 30F INLAND...MID TO UPR 30S URBAN AND
NEARSHORE. FREEZE WARNING LIKELY NEEDED...THOUGH MAYBE NOT FOR ALL
ZONES EAST OF THE BLUE RIDGE LIKE TONIGHT.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
SFC PRESSURE RIDGE/COLD AIR DAMMING PERSISTS WEDNESDAY NIGHT INTO 
SATURDAY...WHEN THE NEXT DISTURBANCE DISLODGES THE ONSHORE FLOW. 
EXPECT BELOW NORMAL TEMPS TO CONTINUE WITH THE ONSHORE FLOW. AREAS 
EAST OF THE RIDGE AXIS BECOME SATURATED BY FRIDAY WITH DRIZZLE OR 
LIGHT RAIN POSSIBLE THEN THROUGH FRIDAY NIGHT. UNCERTAINTY ON 
SOUTHWARD EXTEND OF THE UPPER TROUGH MOVING WEST ACROSS THE NERN 
CONUS ON SATURDAY. CURRENTLY THE 00Z GFS IS MORE AMPLIFIED THAN THE 
00Z ECMWF. THE COOL PATTERN CONTINUES THROUGH AT LEAST SUNDAY AS 
CANADIAN HIGH PRESSURE BUILDING IN BEHIND THE SATURDAY SYSTEM.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
MVFR CIGS AND VSBYS PREVAIL THROUGH THE DAY WITH INTERMITTENT IFR
IN HEAVIER RAIN. ISO THUNDER THREAT TDA EAST OF MRB AHEAD OF THE
FRONT. SLY FLOW GUSTS UP TO 30 KT AHEAD OF THE COLD FRONT THAT IS
APPROACHING FROM THE WEST. STRONG COLD FRONT CROSSES THE TERMINALS
LATE THIS MORNING THROUGH THE EARLY AFTERNOON WITH A QUICK NWLY
WIND SHIFT. GUSTS TO 35 KT LATE THIS AFTERNOON THROUGH TONIGHT
ACROSS THE TERMINALS WITH A FEW SNOWFLAKES POSSIBLE AT THE END OF
PRECIP WEST OF BALT-WASH CORRIDOR.

VFR WEDNESDAY AS HIGH PRESSURE BUILDS NORTHEAST ACROSS THE REGION 
WEDNESDAY. GUSTY NW WINDS EASE THROUGH MIDDAY. ONSHORE FLOW FROM 
COLD AIR DAMMING RIDGE THEN INTO SATURDAY WHEN THE NEXT LOW PASSES 
THE REGION. SUB-VFR CONDS POSSIBLY SPREAD FROM THE EAST FRIDAY AS 
THE ONSHORE FLOW SATURATES.

&&

.MARINE...
SLY SCA LEVEL WINDS ACROSS THE WATERS. HOWEVER...AT 6AM THE SCA
UPGRADES TO A GALE WARNING TO ACCOUNT FOR POSSIBLE SLY GALES IN
HEAVIER SHOWERS LATER THIS MORNING...AS WELL AN EXPECTED LATE AFTN
ONSET OF NWLY GALES BEHIND THE COLD FRONT. GALE WARNING THROUGH
TONIGHT WITH 30-40 KT GUSTS EXPECTED ACROSS THE WATERS.

GALES POSSIBLE FOR LOWER SRN MD WATERS EARLY WEDNESDAY MORNING...BUT 
BUT HAD CONFIDENCE TO SIMPLY ISSUE AN SCA FOR ALL WATERS UNTIL
3PM AND MD BAY WATERS UNTIL 6PM WEDNESDAY AS HIGH PRESSURE BUILDS
NORTHEAST ACROSS THE REGION. ONSHORE FLOW THEN OVER THE REGION
INTO SATURDAY. ELY FLOW 15 TO 20 KT/SCA LIKELY FOR THURSDAY.

&&

.TIDES/COASTAL FLOODING...
POSITIVE TIDAL ANOMALIES REMAIN STEADY ERY THIS MRNG AROUND 3/4 FT
ALONG THE WRN SHORE OF THE CHSPK BAY AND BELOW 1/2 FT IN THE TIDAL
POTOMAC. NO COASTAL FLOODING EXPECTED. 

NWLY GALES TUESDAY NIGHT AND STRONG SCA WINDS INTO WEDNESDAY
AFTERNOON WILL CAUSE BLOWOUT TIDE CONDITIONS FOR THE LOW TIDES ON
WEDNESDAY. OF PARTICULAR CONCERN IS THE MIDDAY/AFTERNOON LOW TIDE
CYCLE WHERE WATER LEVELS LOOK TO DROP TO AROUND 2 FEET BELOW MLLW.

&&

.CLIMATE...
RECORD DAILY HIGH MINIMUM TEMPERATURES WERE SET FOR DCA AND IAD...
AND TIED FOR BWI. BELOW IS A TABLE OF RECORDS FOR APRIL 14 AND LOW
TEMPERATURES OBSERVED.

SITE...PREV RECORD......LOW...
DCA....63F IN 1896......65F...
BWI....62F IN 1896......62F...
IAD....58F IN 1972......63F...

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR DCZ001.
MD...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR MDZ011-013-
     014-016>018.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR 
     MDZ004>007-009-010.
VA...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR VAZ052>057.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR 
     VAZ036>040-042-050-051-501-502.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EDT WEDNESDAY FOR 
     ANZ531>534-537-539>541-543.
     GALE WARNING UNTIL 6 AM EDT WEDNESDAY FOR ANZ530>543.
     SMALL CRAFT ADVISORY FROM 6 AM TO 2 PM EDT WEDNESDAY FOR 
     ANZ530-535-536-538-542.

&&

$$
SYNOPSIS...BAJ/JRK
NEAR TERM...CAS
SHORT TERM...BAJ
LONG TERM...BAJ
AVIATION...BAJ/JRK/CAS
MARINE...BAJ/JRK/CAS
TIDES/COASTAL FLOODING...
CLIMATE...






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