Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 301420
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1020 AM EDT SUN AUG 30 2015

.SYNOPSIS...
HIGH PRESSURE REMAINS OVER THE REGION THROUGH THE END OF THE
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...

HV INCRSD CLD CVR DUE TO THE INFLUX OF MID CLD OVR THE MID ATLC
AND DROPPED TEMPS A FEW DEGS. RMDNR OF FCST LOOKS GOOD.

SYNOPTICALLY...NOT MUCH HAS CHANGED IN THE PAST 24 HRS. HIPRES RDG
STILL RESIDES OVER THE ERN SEABOARD...PERHAPS A LTL BIT FURTHER EAST
THAN SAT MRNG. ALOFT THERE IS A S/SWLY DRIFT...WHICH IS EVIDENT FM
MID-UPR LVL CLDS STREAMING INTO VA.

NOT ONLY IS THERE HIPRES AT THE SFC...BUT THIS RDG EXTENDS UP THRU
H5...PARKED OFF HSE. THUS...SUBSIDENCE SHUD LIMIT INSTBY FOR MUCH OF
THE CWFA. LWR HGTS ACRS THE APLCNS COMBINED W/ TRRN CIRCULATIONS
SUGGEST THAT IF SHRA/TSRA DVLP THE MTNS WL BE THE LOCATION. ATTM
THREAT LOOKS A LTL LESS THAN IT DID FM YDA/S CYCLE...AND HV TRIMMED
THE AREAL CVRG THRU DUSK. 20-30 POPS AT BEST.

PVA APPROACHES AREA TNGT FM THE SW AS A SUBTLE SFC BNDRY DROPS
SWD FM THE GRTLKS. THESE TWO FEATURES SUGGEST THAT NOT ONLY WL
POPS LINGER PAST SUNSET...BUT THE CHC WL SPREAD EAST FM THE MTNS
TWD I- 95. LIKE THE AFTN...PROBS NOT HIGH /20-30 PCT/ AND QPF LVLS
LOW. CLDS MORE CERTAIN THAN PCPN. A MAJORITY OF THE TIME CUD BE
JUST MOCLDY W/O ANY RAIN. WHAT DOES FALLS MAY BE NOT MUCH MORE
THAN SPRNKLS...SPCLY DURING THE OVNGT HRS. HARD TO PROVIDE
SPECIFIC TIMING OTHER THAN HOLDING BACK ACRS THE DC/BALT BURBS
THRU MID EVNG.

&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
DETAIL ISSUES LINGER INTO MON...AS THE SFC BNDRY DSPTS IN/NEAR NRN
CWFA AND PVA/MSTR CONTS TO OVERSPREAD AREA FM THE SW. NEED TO KEEP
BKN CLDS AND LOW END POPS IN THE FCST FOR MUCH OF THE DAY DUE TO
THIS WEAK/DISORGANIZED FORCING...ALTHO CONFIDENCE IN GETTING WET
QUITE LOW. H5 TROF AXIS WL PROGRESS E OF AREA BY LT DAY...AND WL
OFFER UP CLRG DURING THE MID-LT AFTN INTO ELY EVNG IN ITS WAKE. SHUD
BE MOCLR BY OVNGT MON INTO ELY TUE.

AM NOT GOING QUITE A WARM FOR MAXT MON DUE TO CLDS AND PCPN CHCS.
HWVR...AS DEWPTS THREATEN TO REACH THE UPR 60S...CANT SAY THE SAME
FOR MIN-T FCST MON NGT.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
WITH DEPARTING VORT MAX TO OUR EAST...H5 HEIGHT RISES AND VERY POOR
LAPSE RATES...WITH NEARLY MOIST ADIABATIC PROFILES ABOVE LCL...WILL
RESULT IN A DRY DAY ACROSS CWA. THE ONE EXCEPTION WOULD BE IN OUR
FAR WESTERN COUNTIES...WHERE A STRAY AFTERNOON SHOWER OR
THUNDERSTORM COULD DEVELOP. MAIN STORY TUESDAY WILL BE THE
HEAT...WITH MAX TEMPERATURES AOA 90 EAST OF BLUE RIDGE AND IN U80S
WEST OF BLUE RIDGE...OR 5-10 DEGREES ABOVE CLIMO IN MANY SPOTS.
DEWPOINTS REMAIN IN M60S...WHICH WILL KEEP HEAT INDICES NEAR THE
TEMPERATURE.

WEAK UPPER LEVEL DISTURBANCE MOVES THROUGH WEDNESDAY INCREASING THE
CHANCES FOR SHOWERS/THUNDERSTORMS ACROSS THE REGION. WEAK LAPSE
RATES REMAIN...LEADING TO LONG SKINNY CAPE PROFILES...WHICH WILL
PREVENT STORMS FROM REALIZING MAX CAPE. ANY SHOWERS/STORMS WOULD
WEAKEN QUICKLY NEAR SUNSET...WITH STRONG CONVECTIVE RELIANCE ON
INSOLATION.

OUR AREA REMAINS IN NNW FLOW THROUGH THE REMAINDER OF THE
PERIOD...WITH CHANCES FOR DIURNAL SHOWERS AND THUNDERSTORMS EACH
DAY. LACK OF ADDITIONAL LIFTING MECHANISMS BEYOND DAYTIME
HEATING...WILL GENERALLY KEEP ACTIVITY ISOLATED AND THE BEST
CHANCES WEST OF BLUE RIDGE. VERY LITTLE RELIEF FROM THE HEAT WITH
TEMPERATURES REMAINING 5-10 DEGREES ABOVE NORMAL...THOUGH
CONTINUED NORTHWEST FLOW COULD ALLOW FOR A SLIGHT COOLING TREND BY
NEXT WEEKEND.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...

VFR CONDS AND LGT SLY FLOW WL PREVAIL THRU THE DAYLIGHT HRS. THERE
MAY BE A CPL MTN SHRA/TSRA...BUT NONE SHUD IMPACT TERMINALS. PCPN
CHCS SPREAD EAST TNGT BUT STILL REMAIN W OF DC/BALT HUBS. CONFIDENCE
IN ANYTHING AFFECTING MRB/CHO TOO LOW TO MENTION IN TAF ATTM.

OUTLOOK...

MON...LOW PROB SHRA/TSRA LINGER INTO THE DAY...HWVR LOW
CONFIDENCE PRECLUDES TAF MENTION.
TUE...VFR CONDITIONS UNDER HIGH PRESSURE.
WED-THU...LOW AFTERNOON SHOWER/THUNDERSTORM CHANCES RETURN...WITH
BRIEF PERIODS OF SUB-VFR NEAR ACTIVITY.

&&

.MARINE...

SLY FLOW WL CONT THRU MON. THINK THERE WL BE ANOTHER SLY CHANNELING
EVENT TNGT...ALTHO LTST PROGS SUGGEST THAT SCA WONT BE REQUIRED. YDA
THE SAME CUD BE SAID FOR LAST NGT/THIS MRNG...SO WL NEED TO MONITOR
THIS FURTHER.

WINDS EXPECTED TO REMAIN SUB-SCA FROM TUESDAY THROUGH REMAINDER OF
PERIOD. AFTERNOON THUNDERSTORM CHANCES RETURN TO THE WATERS ON
WEDNESDAY AND CONTINUE THROUGH THE REMAINDER OF THE WORKWEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
UPDATE...WOODY!
PRVS...HTS/MSE


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