Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 291342 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
942 AM EDT WED JUL 29 2015

.SYNOPSIS...
WEAK HIGH PRESSURE PERSISTS OVER THE AREA INTO TONIGHT. A COLD FRONT
MOVES THROUGH THE REGION THURSDAY FROM THE WEST. HIGH PRESSURE THEN
PERSISTS OVER THE AREA THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...

12Z IAD RAOB SHOWS MOISTURE EXTENDS DEEPER TODAY UP TO 600 MB AND
PWAT VALUES ARE UP TO 1.75 INCHES. EXTENSIVE LOW CLOUDS AND FOG
THIS MORNING MAY DELAY ONSET OF SHOWERS AND T-STORMS BY A COUPLE
OF HOURS THIS AFTERNOON. STEERING FLOW IS A LITTLE STRONGER AND
BETTER DEFINED TODAY SUGGESTING STORMS WILL MOVE A LITTLE FASTER
BUT MOISTURE IS DEEPER WHICH MAY STILL POSE A THREAT OF HEAVY
RAINFALL.

HEAT INDICES APPEAR WILL GET AWFUL CLOSE TO HEAT ADVISORY CRITERIA
THIS AFTERNOON. SFC DEWPOINTS ARE RUNNING 2-3F HIGHER THAN 24 HRS
AGO. A BIT MORE CLOUD COVER TODAY SHOULD KEEP TEMPS A DEG OR TWO
COOLER THAN YDAY KEEPING HEAT INDICES JUST BELOW 105F. WILL
MONITOR OBS CLOSELY AND ISSUE A HEAT ADVISORY IF NECESSARY.

&&

.TONIGHT...COLD FRONT (NOW STRUNG OUT FROM THE PARENT LOW OVER
ONTARIO) CROSSES THE MID-ATLANTIC WITH PREFRONTAL THUNDERSTORM
CHANCES REACHING THE CENTRAL APPALACHIANS AFTER MIDNIGHT.
OTHERWISE INCREASING CLOUDS WITH MIN TEMPS LOW TO MID 70S.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
THURSDAY...COLD FRONT CROSSES THE CWA THROUGH THE DAY. POPS INCREASE
AHEAD OF THE FRONT THROUGH THE DAY PER DIURNAL TRENDS. FRONT IS A
BIT MORE PROGRESSIVE THAN PREVIOUS...COMES IN QUICKER WITH AFTERNOON
LIKELY POPS FOR BALT-WASH METRO THUNDERSTORMS. MAX TEMPS LOW TO
POSSIBLY MID 90S AHEAD OF THE FRONT. SHOULD IT PUSH THROUGH
SOONER...TEMPS WOULD BE MODERATED. DEWPOINTS IN THE LOW 70S RESULT
IN HEAT INDICES AROUND 100F.

THURSDAY NIGHT...COLD FRONT CLEARS THE SERN ZONES THURSDAY EVENING
WITH COOLER AIR TRAILING. MIN TEMPS 60S WEST OF I-95...LOW 70S
EAST.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
FAIRLY TRANQUIL WEATHER PATTERN FOR LAST DAY OF JULY THROUGH THE
FIRST FEW DAYS OF AUGUST...AS HIGH PRESSURE BUILDS IN FROM THE WEST
BEHIND DEPARTING COLD FRONT. FRONT WILL HAVE MOVED THROUGH THE CWA
BY 8 AM FRIDAY...THOUGH THERE COULD BE A FEW LINGERING SHOWERS OVER
SOUTHERN MARYLAND. NOT MUCH OF A TEMPERATURE CHANGE WITH THIS
FRONT...AS TEMPERATURES EXPECTED TO REMAIN IN THE U80S/L90S. BUT
DEWPOINTS DROP AT LEAST TEN DEGREES...AND GENERALLY REMAIN AOB 65F
THROUGH THE LONG TERM. SLOW WARMING TREND THROUGH TUESDAY...WITH
TEMPS REMAINING A FEW DEGREES ABOVE NORMAL.

PRECIP CHANCES THROUGH THE PERIOD ARE VERY LOW...WITH NO DECENT
SOURCE OF LIFT AND QUALITY LOW-LEVEL MOISTURE SHUNTED OFF TO OUR
SOUTHEAST. WHILE LOW...BEST CHANCES FOR PRECIP OCCUR MONDAY IN OUR
SOUTHERN AND EASTERN ZONES AS MOISTURE RETURN SLOWLY COMMENCES.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
IFR VSBYS/POSSIBLE CIGS THROUGH SUNRISE UNDER WEAK FLOW AND CLEAR
SKIES...PARTICULARLY WHERE IT RAINED LATE TUESDAY. VFR THEN PREVAILS
INTO TONIGHT OUTSIDE OF LOW CHANCES FOR TSTMS...PARTICULARLY NEAR
KCHO THIS AFTERNOON. WEAK COLD FRONT CROSSES TERMINALS THURSDAY WITH
LIKELY THUNDERSTORMS IN THE AFTERNOON FOR DC METROS.

VFR CONDITIONS EXPECTED FRIDAY THROUGH THE REMAINDER OF THE PERIOD
UNDER HIGH PRESSURE.

&&

.MARINE...
SCA FOR SLY CHANNELING THIS EVENING SOUTH OF SANDY PT.
OTHERWISE HIGH PRESSURE. WEAK COLD FRONT CROSSES WATERS THURSDAY
AFTERNOON.

WINDS EXPECTED TO BE SUB-SCA FRIDAY THROUGH THE REMAINDER OF THE
PERIOD UNDER HIGH PRESSURE. LOW CHANCE FOR AFTERNOON THUNDERSTORMS
OVER THE WATERS MONDAY AS LOW LEVEL MOISTURE SLOWLY INCREASES.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 3 AM EDT
     THURSDAY FOR ANZ532>534-537-540-541-543.

&&

$$
SYNOPSIS...BAJ/MSE
NEAR TERM...LFR
SHORT TERM...BAJ
LONG TERM...MSE
AVIATION...BAJ/MSE
MARINE...BAJ/MSE



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