Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 221349
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
949 AM EDT FRI MAY 22 2015

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE AREA TODAY BEFORE PASSING THROUGH
TONIGHT. HIGH PRESSURE WILL BUILD OVERHEAD SATURDAY BEFORE MOVING
OFF THE COAST SUNDAY THROUGH THE MIDDLE PORTION OF NEXT WEEK.
NOTICEABLY HOTTER AND MORE HUMID CONDITIONS ARE EXPECTED NEXT WEEK
AS A SUMMER-LIKE AIR MASS ENTERS THE REGION.

&&

.NEAR TERM /THROUGH TONIGHT/...
CLEAR MORNING ACROSS THE MID-ATLANTIC WITH TEMPS IN THE UPPER
50S LOW 60S...ALREADY SURPASSING THE HIGH TEMPS FROM THURSDAY. A
COLD FRONT IS LOCATED JUST SOUTH OF THE EASTERN GREAT LAKES. THERE
ARE A FEW SHOWERS AHEAD OF THE FRONT BUT HAVE BEEN WEAKENING AS
THE AIRMASS MOVES SOUTHWARD. IS0-SCT SHOWERS ARE EXPECTED TO MOVE
INTO THE NRN POTOMAC HIGHLANDS THIS AFTERNOON AS SHOWN ON THE HRRR.
ISO SHOWERS MAY EVEN REACH BALTIMORE BEFORE DIMINISHING AS THEY
MOVE SOUTH TOWARDS NOVA AND DC.

PREVIOUS DISCUSSION...
IT WILL ALSO BE BREEZY THIS AFTERNOON WITH WINDS GUSTING UP TO 25
KT UNDER A SOMEWHAT TIGHT PRES GRADIENT. UNUSUALLY CHILLY AND
STRONG HIGH PRESSURE WILL BUILD QUICKLY SOUTHWARD AND BE CENTERED
OVER SRN PA BY 12Z SAT. VERY COOL AND DRY AIR MASS ALONG WITH
DIMINISHING WINDS WILL LEAD TO A RAPID DROPOFF IN TEMPS OVERNIGHT
WITH PATCHY FROST LIKELY OVER FAR WRN AREAS. FOR NOW INCLUDED
PATCHY FROST IN GRIDS BUT WILL LET DAYSHIFT MONITOR DEWPOINTS AND
LET THEM DECIDE WHETHER A FROST ADVISORY WILL BE NEEDED OR NOT.
LATEST MOS GUIDANCE SUGGESTS THAT TEMPS WILL FALL LOW ENOUGH FOR
FROST TO FORM IN THAT AREA.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
CANADIAN HIGH PRESSURE WILL REMAIN OVER THE REGION
SATURDAY...RESULTING IN PLENTY OF SUNSHINE ALONG WITH DRY
CONDITIONS. AFTER A CHILLY START...THE SUNSHINE WILL ALLOW FOR
TEMPS TO REBOUND INTO THE LOWER TO MIDDLE 70S FOR MOST AREAS.

THE SURFACE HIGH WILL BEGIN TO SHIFT TOWARD MID-ATLANTIC COAST
SATURDAY NIGHT. A LIGHT SOUTHERLY FLOW WILL ALLOW FOR TEMPS TO BE
A FEW DEGREES WARMER COMPARED FRIDAY NIGHT...BUT IT WILL STILL
TURN OUT CHILLY DUE TO RADIATIONAL COOLING. MIN TEMPS WILL RANGE
FROM THE LOWER AND MIDDLE 40S IN SHELTERED VALLEYS TO THE MID AND
UPPER 50S IN DOWNTOWN WASHINGTON AND BALTIMORE.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
THE SURFACE HIGH WILL CONTINUE TO SHIFT EAST INTO THE ATLANTIC
OCEAN FOR SUNDAY THROUGH THE MIDDLE PORTION OF NEXT WEEK. UPPER-
LEVEL HIGH PRESSURE WILL BUILD OVER THE SOUTHEASTERN CONUS AND THE
UPPER-LEVEL RIDGE AXIS WILL EXTEND NORTH INTO THE MID-ATLANTIC.

THE SOUTHWEST FLOW AROUND THE HIGH WILL ALLOW FOR A WARMING TREND
SUNDAY AND MONDAY. DRY CONDITIONS ALONG WITH PLENTY OF SUNSHINE
ARE EXPECTED DUE TO THE UPPER-LEVEL RIDGE AXIS EXTENDING INTO OUR
AREA.

HOT AND HUMID CONDITIONS ARE EXPECTED FOR THE MIDDLE PORTION OF
NEXT WEEK AS THE SOUTHWEST FLOW CONTINUES. THE HOT AND HUMID
CONDITIONS WILL LEAD TO AN INCREASED CHANCE FOR THUNDERSTORMS
TUESDAY THROUGH THURSDAY...ESPECIALLY DURING THE AFTERNOON AND
EVENING HOURS EACH DAY.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS EXPECTED EVERYWHERE NEXT 30 HRS. SCT AFTERNOON
CLOUDS EXPECTED OVER MRB WITH CIGS 040-050. WINDS GUSTING 20-25 KT
AT ALL TAF SITES XCPT LIGHTER WINDS AT KCHO.

HIGH PRESSURE WILL BRING VFR CONDITIONS AND LIGHT WINDS FOR
SATURDAY THROUGH SATURDAY NIGHT. THE HIGH WILL MOVE OFF THE COAST
SUNDAY AND MONDAY. A SOUTHWEST FLOW IS EXPECTED...BUT VFR
CONDITIONS WILL PERSIST. THERE IS A BETTER CHANCE FOR
THUNDERSTORMS TUESDAY AFTERNOON AND EVENING AS HOT AND HUMID
CONDITIONS INCREASE INSTABILITY.

&&

.MARINE...
SOLID SCA CONDITIONS THIS AFTERNOON WITH GUSTS 20-25KT
ESPECIALLY NORTH.

HIGH PRESSURE WILL REMAIN OVER THE WATERS SATURDAY BEFORE MOVING
OFF THE COAST SUNDAY AND MONDAY. A SOUTHERLY FLOW WILL RETURN
DURING THIS TIME. HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC OCEAN
THROUGH THE MIDDLE PORTION OF NEXT WEEK...ALLOWING FOR THE
SOUTHERLY FLOW TO CONTINUE. A SMALL CRAFT ADVISORY MAY BE NEEDED
FOR PORTIONS OF THE WATERS MONDAY THROUGH TUESDAY NIGHT...BUT IT
WILL BE MARGINAL DUE TO THE RELATIVELY COOLER WATERS.

&&

.CLIMATE...
UNUSUALLY COOL HIGH TEMPERATURES WERE OBSERVED THURSDAY...MAY
21ST. WASHINGTON DULLES BROKE A DAILY RECORD FOR LOW MAXIMUM
TEMPERATURE. THE MAXIMUM TEMPERATURE WAS 58 DEGREES AND THIS
BREAKS THE OLD RECORD OF 59 DEGREES SET BACK IN 2002.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT SATURDAY FOR ANZ539.
     SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ530-
     535-536-538.
     SMALL CRAFT ADVISORY UNTIL 8 AM EDT SATURDAY FOR ANZ531>534-
     537-540>543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...HAS/LFR
SHORT TERM...BJL
LONG TERM...BJL
AVIATION...BJL/LFR
MARINE...BJL/LFR
CLIMATE...LWX


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