National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 141208
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
808 AM EDT TUE MAY 14 2013

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFFSHORE THIS AFTERNOON. A WARM FRONT
ADVANCES NORTHEASTWARD ACROSS THE MID-ATLANTIC STATES TONIGHT. A
COLD FRONT WILL APPROACH THE REGION WEDNESDAY...BUT STALL OUT
THROUGH THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
FROST/FREEZE HEADLINES HAVE EXPIRED.

RDGG WL REMAIN OVER AREA MUCH OF TDA...BUT RTN FLOW WL BE
REALIZED TAFTN. CLDS WL INCR AS A RESPONSE TO WAA...SPCLY WRN AND
CENTRL CWFA.

MSTR INCR AND LWRS TNGT AS A WMFNT CROSSES AREA. GDNC SUGGESTING
SPOTTY/LGT QPF MAY BE SQUEEZED OUT DUE TO ISENT LIFT INVOF FNT. GOOD
UPGLIDE BUT DYNAMICS BETTER NW OF CWFA. HV THEREFORE CONFINED CHC
POPS TO ALLEGHENY FRONT...AND ADDED SCT SPRINKLES ELSW W/IN FRNTL ZN.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
A STORM SYSTEM THAT WILL COVER A LOT OF GROUND TODAY...MOVING ALONG
THE US/CANADIAN BORDER WILL HAVE TO SLOW DOWN AND WAIT OVER THE
GREAT LAKES ON WED. THE LOW WILL BUMP INTO THE SLOWER-MOVING UPPER
WAVE DRIFTING OFF THE COAST OF ERN CANADA. THIS SLOW-DOWN WILL CAUSE
THE COLD FRONT FROM THE FAST-MOVING SYSTEM TO APPROACH THE AREA FROM
THE NORTH AND MEET UP W/ A NEAR-STATIONARY WARM FRONT LAID OUT
ACROSS THE UPPER MIDWEST. AS THESE FEATURES NEAR THE MASON-DIXON
LINE WED AFTN...THEY WILL BE THE FOCUS FOR CONVECTION TO OUR NORTH -
POTENTIALLY DROPPING DOWN ACROSS THE NRN TIER OF THE CWA LATE WED
AFTN/EVE. SVR PARAMETERS WILL BE MARGINAL...BUT ENOUGH TO SUSTAIN
ORGANIZED CONVECTION TO OUR NORTH - DRIVEN BY GOOD MID-LOW LEVEL
SHEAR.

THE SRN HALF OF THE CWA WILL SEE A GOOD WARM-UP AFTER A STRETCH OF
UNSEASONABLY COOL TEMPS AND A DRY AIRMASS. ALL THE DYNAMIC FEATURES
SLIDING BY TO OUR NORTH AND HIGH PRESSURE OFF THE MID ATLC COAST
WILL HELP DEVELOP STEADY SLY BREEZE WED AFTN. THIS WARM AND MOIST
FLOW WILL TAKE TEMPS WELL INTO THE 80S THRU THE AFTN HRS ACROSS THE
SHEN VLY/FOOTHILLS AND PIEDMONT. CLOSER TO THE BAY...THE COOLER
WATERS WILL INFLUENCE AIR TEMPS TO STAY IN THE 70S FOR DAYTIME
HIGHS.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AFTER THE CONVECTIVE ACTIVITY SLIDES OFF THE DELMARVA COAST LATE WED
NIGHT...MORE BATCHES OF RAIN WILL START TO MOVE TOWARD THE APLCNS
FROM THE OHIO VLY. THE STALLED WARM FRONT WILL BE THE FOCUS FOR SOME
SHOWER AND TSTMS ACROSS THE REGION FOR THESE LATE WEEK DAYS. THE
BETTER CHANCE FOR PRECIP WILL BE THU AFTN/EVE AND OVERNIGHT FOR THE
LOWER SW PORTIONS OF THE CWA. THE FRONT WILL BE SQUEEZED IN BETWEEN
HIGH PRESSURE AREAS TO THE NORTH AND SOUTH...ALLOWING FOR AN
ACCELERATED TRAVEL OF PRECIP FROM THE WEST. MUCH OF THE ACTIVITY
THAT DOES CROSS THE MTNS THU AND INTO FRI WILL LARGELY DISSIPATE BUT
MORE LOCALLY HEAVY AND ORGANIZED BATCHES WILL HOLD TOGETHER TO
SPREAD PRECIP ACROSS THE VA/MD PIEDMONT AND COASTAL AREAS.

ANOTHER PASSING UPPER WAVE WILL SWING DOWN ACROSS OUR AREA TO THE
NORTH ON FRI...KEEPING MUCH OF THE FRIDAY PRECIP LIMITED TO THE WRN
HALF OF THE CWA AND SPEC THE HIGHER TERRAIN. MED GUIDANCE IN FAIRLY
GOOD AGREEMENT OF THIS ASPECT OF THE LATER WEEK...TRENDING TOWARD
THIS SOLUTION OF KEEPING THE METRO AREAS AND MOST OF THE NRN HALF OF
THE CWA DRY ON FRI. THIS SAME AIRMASS WILL BE IN PLACE HEADING INTO
THE COMING WEEKEND...BUT THE WRN HALF OF THE CWA WILL SEE POPS
INCREASE FOR SAT AFTN.

ANOTHER LOCALLY STRONG UPPER SHORTWAVE WILL TRAVEL ACROSS THE UPPER
MIDWEST THIS COMING WEEKEND...ADDING COMPLEXITY TO THE FORECAST FOR
EARLY NEXT WEEK AS LARGER AND STRONGER LOW PRESSURE SYSTEM REMAINS
BACK ACROSS THE NRN PLAINS THIS WEEKEND.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
VFR CONDS XPCTD TDA THRU THIS EVNG...BUT CIGS /MID-HIGH DECK/ WL BE
DVLPG TAFTN AND LWRG TNGT. MAY BE ENUF MSTR TO SQUEEZE OUT A FEW
SPRINKLES OVNGT...BUT CERTAINTY FAR FM ENUF TO ADD INTO TAFS...NOT
TO MENTION THERES NO OP IMPACT. THE BIGGER QUESTION IS WHETHER THIS
MSTR MAY LEAD TO ANY MVFR CIGS/VSBYS IN THE 06-12Z WINDOW TMRW...AND
IF ANY VSBY RESTRICTIONS WUD IT BE A RESULT OF PCPN OR FOG DVLPMNT.
CONFIDENCE LOW AND LOCATION MOST LKLY AWAY FM TERMINALS SO THREAT
WONT BE ADDESSED IN PUBLISHED FCSTS.

AN APPROACHING COLD FRONT ON WED AFTN WILL INCREASE THE SLY WINDS
DURING THE DAYTIME HRS...STALLING ACROSS THE REGION AS A WARM
FRONTAL BOUNDARY FOR THU AND INTO EARLY FRI. THIS BOUNDARY WILL
POTENTIALLY GENERATE SCATTERED SHOWERS/TSTMS DURING THE AFTN HRS ON
THU AND FRI...W/ SFC WINDS DECREASING DURING THIS PERIOD.

&&

.MARINE...
AS HIPRES BLDS OVER THE WATERS ELY THIS MRNG...WNDS HV DROPPED BLO
SCA THRESHOLDS. XPCT BACKING WNDS TDA AOB 10 KT AS RTN FLOW DVLPS. A
LLJ/SLY CHANNELING DVLPS LT TNGT. SPDS STRONG ENUF /20-30 KT ABT
1000 FT OFF THE SFC/ BUT AM LESS CERTAIN ABT MIXING AS THERE/S
EVIDENCE OF AN INVSN. HV OPTED FOR STRONG SUB-SCA SUSTAINED WNDS VS
SCA GUSTS.

SLY CHANNELING WILL BEGIN EARLY WED...AS HIGH PRESSURE STRENGTHENS
THE LOW LEVEL WIND FIELD WELL OFF THE MID ATLC COAST. THESE
CONDITIONS WILL SUBSIDE LATE WED AFTER A COLD FRONT MEETS UP W/ A
WARM FRONT...AND THE BOUNDARY STALL OVER THE AREA FOR THE LATTER
HALF OF THE WEEK.

&&

.CLIMATE...
-- Changed Discussion --
AS OF 8 AM...LOWS THIS MRNG WERE
42F AT DCA...
34F AT BWI...
32F AT IAD...

BOTH BWI AND IAD TIED THEIR PREVIOUS RECORD MIN TEMP FOR MAY 14 THAT
WAS PREVIOUSLY SET IN 1996.

THIS MRNG WAS ONLY THE 4TH TIME SINCE 1962 THAT IAD HAS RECORDED
A FREEZING TEMP THIS LATE IN THE SPRING. THE OTHER TIMES WERE 17
MAY 1984 (30F)...22 MAY 2002 (31F)...AND 14 MAY 1996 (32F).

THIS MRNG WAS ONLY THE 4TH TIME SINCE 1873 THAT BALTIMORE RECORDED A
MIN TEMP OF 34F OR COLDER THIS LATE IN THE SPRING. THE OTHER TIMES
WERE 17 MAY 1956 (33F)...21 MAY 2002 (34F)...AND 14 MAY 1996
(34F).
-- End Changed Discussion --

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TO 8 PM EDT WEDNESDAY FOR
     ANZ530>543.
-- End Changed Discussion --

&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS/KLEIN
SHORT TERM...GMS
LONG TERM...GMS
AVIATION...GMS/HTS
MARINE...GMS/HTS
CLIMATE...KLEIN