Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 150800
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
400 AM EDT WED APR 15 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS THE AREA TODAY...AND WILL BE
NUDGED EAST THURSDAY AS AN UPPER LEVEL DISTURBANCE GLIDES TOWARD
THE MID ATLANTIC. A WEAK COLD FRONT WILL CROSS THE REGION
FRIDAY...FOLLOWED BY A SECOND COLD FRONT LATE SATURDAY INTO
SUNDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LTST SFC ANALY DEPICTS HIPRES CENTERED OVER THE GRTLKS ELY THIS
MRNG...WITH ITS RDG AXIS EXTNDG INTO THE MID ATLC RGN. LOPRES MV THE
RECENT CDFNT NOW WELL OFF THE DELMARVA...WITH THE FNT ITSELF ACRS
THE CAROLINAS. GIVEN THE LACK OF LIFT...MOST PCPN HAS DSPTD. THERE
MAY BE A FEW LINGERING SPRINKLES COINCIDENT W/ THE DEEPER MEAN LYR
MSTR...BUT SUPPORT FOR THESE WL DWINDLE AS WELL SOON AFTR SUNRISE.

RDGG WL BUILD THRU THE DAY...W/ THE CWFA W/IN LGT NLY FLOW DRAINING
DOWN THE COAST. WHILE MEAN LYR MSTR WL THIN OUT...AM NOT SO CERTAIN
TAHT WL TRANSLATE TO SUNNY SKIES...AS THERE IS A LOT OF CI E OF THE
MS RIVER. HV PROPPED UP CLD CVR ACRS MD FM GDNC OFFERINGS.

FURTHER SOUTH...MID LVL OVERRUNNING WL KEEP SKIES CLDY AND ENUF MSTR
IN PLACE SUCH THAT LGT RA/DZ OR SPRINKLES STILL WL BE A PSBLTY. POPS
LOW /BARELY 20 PCT HIGHLAND-NELSON CNTY AND LESS TO THE N/ AS DO NOT
BELIEVE THAT MEASUREABLE PCPN WL OCCUR...BUT DO THINK THAT IT/LL BE
A DAMP AND DREARY DAY THERE.

THE XTRM ERN WV PNHNDL DOWN THRU DC TO SRN MD WL BE BTWN THESE TWO
EXTREMES. AM NOT CERTAIN EXACTLY HOW THE GRADIENT WL PLAY OUT...AND
THIS AREA HAS THE BETTER CHC AT FCST ADJUSTMENTS DURING THE COURSE
OF THE DAY.  THAT MAY PLAY INTO MAXT SLGTLY...BUT THERES NOT A HUGE
SPREAD TO START WITH.  USED A SUPERBLEND OF ALL OFFERINGS TO IRON
OUT MESOSCALE DIFFS NOTED.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
RDGG SHUD HV A FIRMER CONTROL OF WX TNGT...SO HV CLRD OUT SKIES JUST
ABT AREAWIDE.  THIS MAY BE WORDED AS PTCLDY FOR CENTRAL VA DUE TO
THE CLOUDIER START AND POTL FOR A FEW LINGERING CLDS OVNGT. IN SPITE
OF HIPRES...STILL BELIEVE WE WL HV A SLGT NELY DRAINING TAKING PLACE
AND CONSEQUENTLY WL HV LGT FLOW IN WIND GRIDS. MIN-T WL BE ON THE
COOL SIDE...LWR-MID 40S COMMON.

WHILE THE SFC RIDGE AXIS WL HOLD INTO THU...RETURN FLOW WL COMMENCE.
EXACTLY TO WHAT EXTENT STILL VERY MUCH IN DOUBT. A KEY DETERMINING
FACTOR WL BE THE PRESENCE/STRENGTH/LOCATION OF DVLPG CSTL LOPRES.
NAM DECIDEDLY FURTHER NW THAN THE REST /INLAND OVER ERN NC/ AND WAS
NEGLECTED. HWVR...GEFS MEMBERS ALL OVER THE PLACE W OF THE APLCNS.
WOULD THINK THAT WUD HV A DOWNSTREAM IMPACT AS WELL. RESULTANT FCST
HAS SOMEWHAT LOW CONFIDENCE IN DETAILS.

HWVR FROM A BIG PICTURE PERSPECTIVE...THERE IS AGREEMENT THAT MID
LVL S/WVS WL HEAD TWD US...AND ELY/SELY SFC SLOW TRANSPORTING MARINE
MSTR AND SLY/SWLY MID LVL FLOW ARE A RECIPE FOR POTL PCPN. USED A
BLENDED APPROACH W/ HVY REPRESENTATION FROM SREF. CHOSE WX TYPE RA
DUE TO THE OVERRUNNING NATURE OF SETUP. THU WL BE THE PD WHEN POPS
RAMP UP THRU CHC TO LKLY IN THE MTNS...AND WL BE SPREADING EWD THU
EVNG.

USED A SILMR APPROACH TO TEMP FCST MAXT THU...AND WENT A BIT ON THE
WARM SIDE OF THE BLEND FOR MIN-T THU NGT DUE TO SUSPECTED DEWPT
ADVCTN.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
HIGH PRESSURE WILL BE OFF THE EAST COAST FRIDAY. A DISTURBANCE IS
EXPECTED TO CROSS THE MID-ATLANTIC INTO FRIDAY AND RAIN SHOULD
MOVE FROM WEST TO EAST FRIDAY MORNING WITH THE GREATEST CHANCE
ACROSS THE NRN CWA. RAINFALL AMTS SHOULD BE LESS THAN A QUARTER
INCH. WESTERLY FLOW BEHIND THE TROUGH AXIS SHOULD ADVECT DRIER AIR
BY FRIDAY EVENING. A WEAK COLD FRONT MAY CAUSE LIGHT RAIN TO
LINGER INTO FRIDAY NIGHT.

A SECOND AREA OF HIGH PRESSURE WILL MOVE INTO THE REGION FRI NIGHT-
SATURDAY. MODEL SPREAD EXISTS THIS WEEKEND AS A LARGE UPPER LEVEL
LOW SPINS ACROSS THE CENTRAL PLAINS. RIDGING ACROSS THE MID-ATLANTIC
SHOULD KEEP RAIN TO THE SOUTH AND WEST SATURDAY. MEANWHILE...LOW
PRESSURE WILL BE INTENSIFYING ACROSS THE TN VALLEY TRACKING
NORTHWARD. GFS/ECMWF ARE SHOWING ANOTHER WEDGE TO FORM SUNDAY. AT
THIS TIME...CONFIDENCE IS LOW FOR THE ONSET OF RAIN AS MODEL SPREAD
EXISTS. HOWEVER...RAIN IS EXPECTED TO MOVE INTO THE VA HIGHLANDS AND
OHIO VALLEY BEFORE MOVING NORTHWARD ACROSS THE MID-ATLANTIC BY
MONDAY MORNING. MODERATE TO HEAVY RAINFALL IS POSSIBLE INTO MONDAY
MORNING. LOW PRESSURE WILL BECOME MORE ORGANIZED MONDAY. RAIN IS
POSSIBLE THROUGH MONDAY.

DRIER AIR WILL FILTER IN BEHIND THE SFC LOW TUESDAY. TEMPS SHOULD BE
HIGHER THAN NORMAL FRIDAY AND SATURDAY THEN DIP TO NEAR NORMAL
TOWARDS THE END OF THE LONG TERM.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDS WL PREVAIL THRU THE VALID TAF PD. MOST CIGS MID LVL
ATTM...AND SHUD BE RISING TO HIGH LVL DURING THE DAY. CHO HAS DIPPED
TO MVFR ONCE SINCE 06Z...AND WONT RULE OUT THAT HPPNG AGN BEFORE
12Z. SINCE CHO NEARER TO DEEP MSTR...ITLL BE A STEP OR TWO BHD THE
REST OF THE TERMINALS THRU THE DAY.

SKIES WL CLR OUT TNGT. AGN...THAT MAY SPELL PTCLDY FOR CHO.

RETURN MOST WL OVERSPREAD TERMINALS THU-THU EVNG. CHO-MRB WL BE
AFFECTED DURING THE AFTN...THE THE DC-BALT METROS WL SEE IT IN THE
EVNG. MVFR PSBL ONCE PCPN ARRIVES...AND IT/LL BE LKLY THU EVNG/OVNGT.

LOW CIGS/VSBYS RESULTING IN POSSIBLE FLIGHT RESTRICTIONS FRIDAY.

&&

.MARINE...
NLY FLOW HAS DIMINISHED ACRS WATERS SUFFICIENTLY TO CANX SCA FOR
MID BAY/LWR PTMC ELY. NLY FLOW SHUD CONT THRU THE DAYLIGHT HRS AND
BECOME NELY TNGT. FOR THE MOST PART WINDS SHUD BE 10 KT OR LESS.

ELY FLOW INCREASES THU...FEEDING PCPN WHICH WL BE SPREADING EAST.
WHILE THERE IS CONSIDERABLE UNCERTAINTY IN SPECIFICS...GDNC DOES
AGREE THAT MEAN MIXED LYR WINDS WL BE NEAR IF NOT EXCEEDING SCA
THRESHOLDS. HV OPTED TO RAISE SCA STARTING AT 11AM THU...AND CONTG
TO THE END OF THE THU PD. ONCE PCPN ARRIVES...WHICH WL BE LATE
DAY OR ELY EVNG...FVRBL DOWNWARD TRANSPORT SHUD COME TO A RAPID END.

LOW PRESSURE WILL MOVE SOUTH OF THE WATERS FRIDAY. HIGH PRESSURE
MOVES IN SATURDAY.

&&

.EQUIPMENT...
NWR CHARLOTTESVILLE OPERATING IN DEGRADED MODE DUE TO TELCO ISSUES.
TECHS ARE AWARE OF THE SITUATION...BUT IT MAY BE SEVERAL DAYS BEFORE
A FIX IS IN PLACE.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EDT THURSDAY FOR
     ANZ530>543.

&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS
SHORT TERM...HTS
LONG TERM...HAS
AVIATION...HAS/HTS
MARINE...HAS/HTS
EQUIPMENT...HTS



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