Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180130 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 930 PM EDT FRI APR 17 2015 .SYNOPSIS... A SURFACE TROUGH WILL PASS THROUGH THE REGION TODAY. HIGH PRESSURE WILL RETURN FOR SATURDAY. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND A WARM FRONT WILL ACROSS THE AREA SUNDAY NIGHT INTO MONDAY. A COLD FRONT WILL PASS THROUGH LATE MONDAY INTO MONDAY NIGHT BEFORE HIGH PRESSURE RETURNS FOR THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/...
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THE LOSS OF HEATING HAS PUT AN END TO ALL BUT A FEW LINGERING SHOWERS NEAR THE CNTRL CHES BAY LATE THIS EVE. OUTFLOW BOUNDARIES SOME WEAK LEFTOVER INSTABILITY FROM A WARM AFTN ARE SUPPLYING THE ONGOING ACTIVITY. A RECENT FORECAST UPDATE WAS SENT W/ THE INCREASED POPS FOR THIS RELATIVELY SMALL ZONE OF SHOWERS S OF THE BALT METRO AND SURROUNDING THE ANNAPOLIS AREA. STILL A WARM EVE W/ DEWPOINTS STILL FAIRLY HIGH COMPARED TO RECENT TRENDS. MAX TEMPS EARLIER THIS AFTN WERE WELL ABOVE AVG...NEARLY 15F ABOVE AVG AT ALL 3 METRO AIRPORTS W/ A HIGH NEAR 80F. USED A ECM/ADJMAV BLEND FOR OVERNIGHT LOWS...INCREASING THEM SLIGHTLY ESPC FOR THE I-95 CORRIDOR W/ THE HIGHER DEWPOINTS EVEN AFTER A WEAK COLD FRONT SLIDES THRU EARLY THIS MRNG. USED THE SAME BLEND FOR HIGHS ON SAT...BUT ALSO RAISED TEMPS A BIT FROM PREV FORECAST. HIGH PRESSURE BUILDING IN FROM THE NORTH WILL BRING IN A LIGHT NLY WIND...WHICH IS RELATIVELY COOLER AND DRIER BUT W/ AMPLE SUN AND LOWER DEWPOINTS...GOOD SUBSIDENCE SHOULD ALLOW FOR ENOUGH BL MIXING AND SFC TEMPS CLIMBING BACK INTO THE U70S/L80S BY MIDDAY.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... SIMILAR PATTERN TO WEDNESDAY NIGHT THROUGH THURSDAY NIGHT EXPECTED SATURDAY NIGHT THROUGH SUNDAY NIGHT. MUCH MORE RAIN IS EXPECTED SUNDAY NIGHT THAN THURSDAY NIGHT. A FLOOD THREAT BEGINS LATE SUNDAY NIGHT AND CONTINUES THROUGH MONDAY. HIGH PRESSURE BUILDS IN FROM THE NORTH SATURDAY NIGHT...WITH A DRY WEDGE IN PLACE BY SUNDAY MORNING. A POTENT LOW LIFTING NORTH FROM THE MID-SOUTH TO THE MIDWEST BRINGS A DEEP PLUME OF GULF MOISTURE TO THE REGION THROUGH THE DAY SUNDAY. PRECIP WILL BE SLOW TO SCOUR OUT THE DRY WEDGE SUNDAY...BUT RAIN...HEAVY AT TIMES...IS EXPECTED TO LIFT ACROSS THE AREA SUNDAY NIGHT. SATURDAY NIGHT...MINS MID TO UPR 40S INLAND...LOW 50S NEARSHORE/URBAN AS A NORTH WIND MIXES FROM SFC HIGH CROSSING NEW ENGLAND. WIND STRONGEST EAST OF THE BLUE RIDGE. CLEAR WITH HIGH CLOUDS INCREASE LATE IN THE NIGHT. SUNDAY...SFC HIGH CENTER DRIFTS EAST FROM CAPE COD AND WITH SFC RIDGE STRETCHING SW ACROSS THE CENTRAL MID-ATLANTIC. SFC FLOW BECOMES ELY WITH DEEP GULF PLUME LIFTING NORTH AS A WARM FRONT FROM THE CAROLINAS TO VIRGINIA...AND OVER TO THE MIDWEST. RAIN BREAKS OUT OVER THE SWRN THIRD OF THE CWA IN THE AFTERNOON. WITH ONSHORE FLOW...EXPECT RAIN ALONG ERN SLOPES OF BLUE RIDGE AND WEST FROM THERE. PERHAPS ONE TO TWO TENTHS INCH BEFORE SUNSET WEST OF CHARLOTTESVILLE. SUNDAY NIGHT...SWATH OF MODERATE WITH LOCALLY HEAVY RAIN LIFTS NORTH ACROSS THE CWA. RAISED 100 POPS FOR THE ENTIRE CWA AS THIS IS NOT A POP FORECAST BUT A QPF. EXPECT ABOUT AN INCH ACROSS THE AREA. ENHANCEMENTS COME ON THE ERN SLOPES OF THE BLUE RIDGE AND EAST OF A MESOLOW TRACK WHICH SHOULD BE ROUGHLY ALONG THE BLUE RIDGE PER GFS AND FARTHER EAST FROM THE ECMWF (WILL NEED TO MONITOR HOW GUIDANCE HANDLES THIS MESO FEATURE THROUGH THE NEXT DAY TO HELP DETERMINE FLOOD AND WIND THREAT). LLJ OF 50KT AROUND 2 KFT LOOKS TO LIFT EAST OF I-95 LATE IN THE NIGHT. LOW THUNDER THREAT IN THIS AREA...BUT WITH AMPLE RAIN TO MIX THIS WIND DOWN...THERE IS A LOW WIND THREAT. WILL ADD LOW WIND AND FLOOD THREAT TO THE HWO. MIN TEMPS UPR 40S WEST OF BLUE RIDGE/LOW TO MID 50S EAST. && .LONG TERM /MONDAY THROUGH FRIDAY/... THERE IS A FAIR AMOUNT OF UNCERTAINTY WITH REGARDS TO TEMPS...TIMING...AND TSTM DEVELOPMENT AFTER THE INITIAL WAVE OF PRECIP EXISTS OUR AREA TO THE EAST MON MORNING. AS SUCH...FORECAST FOR MON AFTERNOON IS HIGHLY CONDITIONAL AND SUBJECT TO LARGE SWINGS IN TEMP/PRECIP POTENTIAL. WARM FRONT LIKELY BEGINS THE DAY NEAR THE VA/NC BORDER AND SLOWLY LIFTS NORTH THROUGH THE DAY. SOUTH OF THE FRONT...DEWPOINTS IN THE 60S AND TEMPERATURES IN THE 70S WILL YIELD MODERATE INSTABILITY. DESTABILIZATION IS LIKELY OVER PARTS OF THE MID-ATLANTIC...WITH ENOUGH DEEP LAYER SHEAR FOR STRONG/SEVERE THUNDERSTORMS. HOW QUICKLY AND HOW MUCH OF OUR CWA IS IN WARM SECTOR WILL EFFECT WHICH LOCATIONS ARE IMPACTED...IF ANY. AT THIS TIME...STILL APPEARS HIGHEST CHANCES FOR STRONG TSTM DEVELOPMENT IS FROM DC SOUTHWARD...WHERE GREATEST HEATING SHOULD OCCUR. COLD FRONT MOVES THROUGH THE AREA MON NIGHT AND BRINGS DRIER AIR TO THE REGION FOR THE EXTENDED PERIOD. HOWEVER...BROAD UPPER LOW TO OUR NORTH WILL KEEP WEATHER UNSETTLED THROUGH THE WEEK...WITH CHANCES FOR LIGHT PRECIP IN PARTS OF THE CWA WED AND THURS. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
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CLOUDS/PRECIP NEARLY OUT OF THE AREA AND CERTAINLY NOT A FACTOR FOR AREA TAF SITES HEADING INTO THE LATE NIGHT HRS. VFR CONTINUES SATURDAY WITH LIGHT NORTHERLY FLOW. VFR SATURDAY NIGHT THROUGH SUNDAY. HIGH PRESSURE BUILDS NORTH OF THE AREA SATURDAY NIGHT WITH N WINDS GUSTING 15 TO 20 KT EAST OF THE BLUE RIDGE. FLOW BECOMES ELY SUNDAY AS THE HIGH CENTER DRIFTS OFF NEW ENGLAND. STRONG LOW LIFTS INTO THE MIDWEST LATE SUNDAY THROUGH MONDAY. WARM FRONT AND DEEP MOISTURE PLUME LIFTS OVER THE AREA LATE SUNDAY AFTERNOON THROUGH SUNDAY NIGHT. HEAVY RAIN/IFR CONDS ACROSS THE DC METROS MIDNIGHT THROUGH LATE SUNDAY NIGHT. LLWS CONCERNS PSBL MON MORNING WITH SE WINDS 40-50 KT AT 2KFT...SHIFTING TO THE SOUTH DURING THE MORNING. SUB-VFR CONDITIONS POSSIBLE MON AFTN AS A COLD FRONT BRINGS ANOTHER ROUND OF PRECIP TO THE AREA. CHC OF THUNDER FOR THE TAF SITES FOR MON AFTN/EVENING. VFR CONDITIONS RETURN LATE MON NIGHT AS THE PRECIP DIMINISHES.
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&& .MARINE...
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HIGH PRESSURE BUILDS IN TONIGHT AND SATURDAY...WITH GENERALLY LIGHT N WINDS. NORTH WINDS CHANNEL DOWN THE BAY LATE SATURDAY EVENING THROUGH THE LATE NIGHT. SCA FROM 10PM FOR NRN MD WATERS...THEN ALL BUT THE UPPER TIDAL POTOMAC 2AM TO 6AM. WILL NEED TO SEE IF ALL WATERS NEED TO BE IN AND IF IT EXTENDS INTO SUNDAY. FLOW BECOMES ELY SUNDAY MORNING AS HIGH PRESSURE CENTER MOVES OFF THE NEW ENGLAND COAST. WARM FRONT WITH HEAVY RAIN AND GUSTY SHOWERS CROSSES THE WATERS SUNDAY NIGHT. SMW OR GALE LIKELY. SCA CONDITIONS DURING THE DAY MON AHEAD OF THE COLD FRONT. SCA POSSIBLE TUES AFTERNOON BEHIND ANOTHER COLD FRONT.
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&& .EQUIPMENT... AUDIO DEGRADATION AT THE NOAA WEATHER RADIO CHARLOTTESVILLE TRANSMITTER IS EXPECTED TO CONTINUE THROUGH THIS WEEKEND. TECHNICIANS ARE SCHEDULED TO PERFORM MAINTENANCE AT THE TRANSMITTER SITE MONDAY. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 PM SATURDAY TO 6 AM EDT SUNDAY FOR ANZ530>532-538>540. SMALL CRAFT ADVISORY FROM 2 AM TO 6 AM EDT SUNDAY FOR ANZ533- 534-536-537-541>543.
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&& $$ UPDATE...GMS PREV DISCUSSION...KCS/BAJ/MSE

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