National Weather Service National Headquarters

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

000
FXUS61 KLWX 130241 AAB
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1041 PM EDT WED JUN 12 2013

.SYNOPSIS...
A COLD FRONT WILL REMAIN STALLED OUT NEAR THE MASON-DIXON LINE.
LOW PRESSURE WILL RIDE ALONG THE BOUNDARY...IMPACTING THE AREA
TONIGHT AND THURSDAY. THE COLD FRONT ASSOCIATED WITH THE LOW WILL
PASS THROUGH LATE THURSDAY AND HIGH PRESSURE WILL BUILD TOWARD THE
REGION FRIDAY AND THIS WEEKEND.

&&

.NEAR TERM /THROUGH THURSDAY/...
TONIGHT - UNTIL THURS MRNG.
THE MID ATLC CONTINUES TO DESTABILIZE HEADING INTO THE LATE NIGHT
HRS. STILL...PORTIONS OF THE N CNTRL VA PIEDMONT/FOOTHILLS ARE
MAINTAINING A COUPLE THOU J/KG OF AVAILABLE ATMOS ENERGY...BUT THE
750MB CAP - ON THE 00Z KIAD SNDG - WILL ONLY BECOME STRONGER AS
THE LOW LEVELS CONTINUE TO COOL. A NUMBER OF LARGE AND POTENT SVR
STORMS HAVE DEVELOPED ACROSS CNTRL OHIO...THROUGH THEY ARE FEEDING
OFF A LOCAL BOUNDARY ARE ONLY SLOWLY DRIFTING TOWARD THE ESE. MORE
POTENT AND OMINOUS BATCHES OF CONVECTION ARE BEGINNING TO CONGEAL
ACROSS THE I-90 CORRIDOR OF THE UPPER MIDWEST.

WITH THE LOSS OF DAYTIME HEATING...MODIFICATIONS IN THE UPPER
LEVEL WIND FIELD AND THE LONG DISTANCE THAT THIS FEATURE HAS TO
TRAVEL - THE POTENTIAL FOR DIRECT IMPACTS ON THE CWA DECREASE. A
REINVIGORATED MCS THAT MOVES DUE SE AND GAINS STEAM AS IT GOES IS
NOT OUT OF THE QUESTION...ESPECIALLY W/ THE LARGE STRATIFICATION
OF INSTABILITY LEADING THE WAY AHEAD OF THESE STORMS...BUT THERE
ARE ALSO FORCES WORKING AGAINST THE MORE AGGRESSIVE PROG AND
WOULDN`T BE SURPRISED TO ONLY A FRACTION OF THE UPPER MIDWEST
ACTIVITY CROSS OVER THE MTNS AND SPREAD WIDESPREAD STRATIFORM
(LIGHT-MODERATE) RAIN AS STORMS TRACK SEWD AND DISSIPATE AS THEY
PROGRESS.

LOCAL GUIDANCE CONTINUES TO LABEL THE SWRN CWA...THE
LOWER SHEN VLY/I-64 CORRIDOR...FOR THE BEST POTENTIAL FOR A
COMBINATION OF NEW DEVELOPMENT AND RESIDUAL ACTIVITY FROM THE
CURRENT UPPER MIDWEST TSTMS. AS OF 1030PM...SOME MINOR CONVECTIVE
ACTIVITY DEVELOPING IN NRN WV...BETWEEN I-77 AND I-79 WHICH COULD
EVENTUALLY HELP INITIATION FURTHER EAST.

THURS AFTN... /PREV DISC/
12Z MODELS SHOW SMALL DIFFERENCES WITH TIMING OF THE FRONT DURING
THE DAY BUT CURRENT THINKING IS FROPA WILL OCCUR LATE ENOUGH IN
THE DAY TO ALLOW FOR STRONG PRE-FRONTAL DESTABILIZATION EAST OF
THE BLUE RIDGE DURING THE MRNG ALTHOUGH THERE IS SOME UNCERTAINTY
WITH HOW DEBRIS CLOUDS FROM THE OVNGT MCS WILL IMPACT HEATING
INITIALLY. 09Z SREF SHOWS A DECENT CHANCE /GREATER THAN 40
PERCENT/ OF SBCAPE VALUES GREATER THAN 2000 J/KG BY THE AFTN FROM
I-95 EAST.

COMBINED WITH STRONG WINDS ALOFT /BULK SHEAR VALUES 40 KT OR
GREATER/ AND DEEP LIFT...STORMS ARE EXPECTED TO QUICKLY ORGANIZE
DURING THE MIDDAY. DEEP-LAYER SHEAR PARALLEL TO THE FRONTAL
BOUNDARY FAVOR A LINEAR MODE OF CONVECTION WITH A LARGE BOWING
SEGMENT CERTAINLY POSSIBLE. SPC HAS PLACED AREAS EAST OF THE BLUE
RIDGE IN A MODERATE RISK FOR TOMORROW. THE GREATEST THREAT WILL BE
WIDESPREAD DAMAGING WINDS. LARGE HAIL AND A FEW TORNADOES WILL BE
POSSIBLE. BASED ON THE EXPECTED LOCATION OF THE WARM FRONT...THERE
WOULD BE AN ENHANCED RISK FOR A TORNADO NEAR THE MASON-DIXON LINE.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
LOPRES MVG OFF THE CST THU NGT...W/ ANY RESIDUAL SHRA EXITING DURING
THE EVNG HRS. LT EVNG THRU THE OVNGT SHUD BE DRY...W/ CLRG SKIES AS
NW WINDS PICK UP. THE SURGE OF DRIER AIR WL BE THE BIGGER IMPACT...
AS 30-35 KT AVBL IN H9-8 LYR...ALL W/ FVRBL MIXING POTL. HV INFUSED
SOME 30 MPH WIND GUSTS IN THE DATABASE BHD THE LOW...BUT GRDLY TAPER
THEM OFF OVNGT.

H5 TROF AXIS STEEPENS BY FRI MRNG...PROVIDING SOME STEEP LAPSE
RATES. THE MITIGATING FACTOR WL BE DOWNSLOPING WINDS/INCRSG
SUBSIDENCE FM BLDG SFC HIGH. HWVR...FEEL ITS PRUDENT TO HV SCHC/CHC
SHRA IN THE GRIDS...PRIMARILY FOR THE MID AFTN HRS. ONCE DIURNAL
MIXING RESUMES...BRZY CONDS WL RETURN. THE SYNOPTIC SCALE WNDS WL
DIMINISH BY MIDDAY...OUTSIDE OF ANY LCL GUSTS INVOF SHRA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
HIGH PRESSURE BUILDS IN OVER THE WEEKEND FOR WHAT SHOULD BE A QUIET
WEEKEND. SATURDAY LOOKS SUNNY AND SEASONABLE. TEMPERATURES CREEP UP
ON SUNDAY AS A WARM FRONT MOVES THROUGH. THERE MAY BE MORE
CLOUDS...BUT THE CURRENT THINKING IS THAT ANY CONVECTION REMAINS TO
THE NORTHWEST OF THE CWA.

THE NEXT FRONT IS FORECAST TO AFFECT THE CWA MONDAY-TUESDAY OF NEXT
WEEK WITH A CHANCE OF SHOWERS AND THUNDERSTORMS.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS EXPECTED THIS AFTERNOON AND EVENING.

TWO ROUNDS OF TSTMS POSSIBLE TONIGHT AND TOMORROW. FIRST ROUND
WOULD LIKELY BE OVERNIGHT...WITH POTENTIAL FOR HEAVY RAIN AND
GUSTY WINDS. VSBYS MAY BE REDUCED FOR RAIN AND FOG. 2ND ROUND OF
STORMS WOULD BE DURING THE DAY TOMORROW...LIKELY LATE MORNING TO
EARLY AFTERNOON FOR KMRB AND AFTER NOON FOR OTHER TAF SITES. THESE
STORMS MAY PRODUCE DAMAGING WINDS AND LARGE HAIL...ALONG WITH
PERIODS OF REDUCED VSBYS. FORECAST UPDATES LATER THIS EVENING AND
OVERNIGHT WILL REFINE TIMING AND IMPACTS OF THESE STORMS. WIND
GUSTS UP TO 20-25KT FROM THE S-SW EXPECTED DURING THE LATE
MORNING-AFTERNOON HOURS THU.

PRIMARILY VFR EXPECTED FRI THROUGH SUNDAY. THERE IS A CHANCE OF
SCATTERED SHOWERS/TSTMS FRI AND LATE SUNDAY...WITH POTENTIAL OF
BRIEF SUB-VFR CONDITIONS.

&&

.MARINE...
SHOWERS AND THUNDERSTORMS MAY IMPACT THE WATERS OVNGT. ANY
THUNDERSTORMS THAT DO DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE
GUSTY WINDS.

SOUTHERLY WINDS INCREASE TO BETWEEN 20-30 KT AHEAD OF A COLD FRONT
ON THURSDAY. A SMALL CRAFT ADVISORY IS IN EFFECT ACCORDINGLY.
WIDESPREAD THUNDERSTORMS ARE EXPECTED AHEAD OF A COLD FRONT THURSDAY
AFTERNOON WITH THE POTENTIAL FOR DAMAGING WINDS. IT WILL LIKELY BE
EXTREMELY HAZARDOUS TO BE ON THE WATERS THU AFTN.

A NWLY SURGE WL COME BHD DEPARTING LOPRES THU NGT...W/ 30-35 KT
AVBL ASSUMING FULL MIXING. AM UNCOMFORTABLE MAKING THAT ASSUMPTION
LT IN THE EVNG FLLWG NMRS TSRA...BUT DO RECOGNIZE A SYNOPTIC SCALE
STRONG WND THREAT...SPCLY IN THE EVNG. WL THEREFORE RAISE A HIGH
END SCA FOR THU...KEEPING THE GLW PSBL WORDING IN THE SYN AND HWO.
THE SCA POTL LASTS INTO FRI...ALTHO THE WND GUSTS/SPDS WL GRDLY BE
DIMINISHING OVNGT AND THRU FRI. WL CONT SCA EVERYWHERE TIL 17Z
/1PM/ AS A STARTING POINT. ANTICIPATE FOR SOME WATERS...MD BAY
MAYBE?...THAT THE SCA MAY BE REQD LONGER.

&&

.HYDROLOGY...
FLASH FLOOD WATCH IN EFFECT FOR THE CWA TNGT AND THU. WET
ANTECEDENT CONDITIONS HAS RESULTED IN A 1-HR FFG AROUND AN INCH.
THERE IS A POTENTIAL FOR A COMPLEX OF SHOWERS AND STORMS OVER THE
OH VLY TO CROSS THE APPALACHIANS THIS EVE AND TRACK ACROSS THE
AREA LATE TNGT. IF THE COMPLEX HOLDS UP...IT WILL HAVE THE
POTENTIAL TO PRODUCE HVY DOWNPOURS WITH A QUICK INCH IN AN HOUR
POSSIBLE. THE BEST CHANCE FOR RAIN TNGT WILL BE OVER NRN MD AND
THE ERN WV PANHANDLE...WHERE A FRONTAL BOUNDARY RESIDES.

STEADY HEAVIER RAIN IS MORE LIKELY NORTH OF THE AFOREMENTIONED
BOUNDARY...WHICH LIKELY PUTS WIDESPREAD HEAVY PRECIPITATION NORTH OF
THE AREA ON THU. HOWEVER...EVEN CONVECTIVE ACTIVITY THAT DEVELOPS
SOUTH OF THE WARM FRONT WILL DEFINITELY BE CAPABLE OF PRODUCING 1-2
INCHES OF RAINFALL IN A SHORT PERIOD OF TIME.

&&

.TIDES/COASTAL FLOODING...
WINDS WILL BECOME SOUTHERLY AND GUSTY THURSDAY AFTERNOON AHEAD OF AN
APPROACHING STRONG COLD FRONT. ANOMALIES WOULD NEED TO REACH
APPROXIMATELY 3 FT FOR TIDAL FLOODING. WIND SPEED/DIRECTION WILL BE
FAVORABLE FOR INCREASED ANOMALIES FOR A FEW HOURS DURING THE
DAY...BUT IS NOT EXPECTED TO PRODUCE ANOMALIES THAT WOULD THREATEN
COASTAL FLOOD THRESHOLDS. HOWEVER...ANY LOCATIONS SUSCEPTIBLE TO
FLASH FLOODING FROM HEAVY RAINFALL AS WELL WILL STILL NEED TO
MONITOR THE SITUATION...AS THOSE THRESHOLDS ARE QUITE LOW. PLEASE
REFER TO THE HYDROLOGY SECTION.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLASH FLOOD WATCH THROUGH THURSDAY EVENING FOR DCZ001.
MD...FLASH FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR MDZ003-501-
     502.
     FLASH FLOOD WATCH THROUGH THURSDAY EVENING FOR MDZ004>007-
     009>011-013-014-016>018.
VA...FLASH FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR VAZ025>031-
     036-037-503-504.
     FLASH FLOOD WATCH THROUGH THURSDAY EVENING FOR VAZ038>040-042-
     050>057-501-502.
WV...FLASH FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR WVZ050>053-
     055-501>506.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM THURSDAY TO 1 PM EDT FRIDAY
     FOR ANZ530>543.

&&

$$
UPDATE...GMS
PREV DISCUSSION...JRK/HTS/KCS/BPP