Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 301901 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 301 PM EDT TUE SEP 30 2014 .SYNOPSIS...
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LOW PRESSURE OVER THE GREAT LAKES WILL TRACK EAST ACROSS THE MIDDLE ATLANTIC REGION TONIGHT AND WEDNESDAY. HIGH PRESSURE WILL RETURN TO THE EAST COAST LATER WEDNESDAY AND REMAIN IN PLACE UNTIL A COLD FRONT APPROACHES THE AREA FRIDAY. A COOLER AND DRIER AIRMASS WILL FOLLOW FOR THE WEEKEND AND EARLY NEXT WEEK.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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UPPER CUTOFF LOW WILL GRADUALLY PULL OUT OF THE GREAT LAKES REGION AND MOVE ACROSS THE MIDDLE ATLANTIC AND NORTHEAST TONIGHT AND WEDNESDAY. UPPER DYNAMICS ASSOCIATED WITH THE UPPER LOW WILL CONTINUE TO SPREAD EAST ACROSS THE FORECAST AREA. LAPS ANALYSIS SHOWS THE BEST INSTABILITY WEST OF THE BLUE RIDGE AND OVER THE NORTHWEST THIRD OF THE FORECAST AREA WHERE CAPES ARE RUNNING AT 500-800 J/KG WITH NO CIN. BEST CHANCES FOR SHOWERS AND ISOLATED STORMS WILL OCCUR OVER THESE AREAS AND ALONG THE MASON/DIXON LINE. COOLING ALOFT FROM THE UPPER LOW WILL LEAD TO SOME STEEPENING OF MID LEVEL LAPSE RATES. A FEW OF THE STORMS COULD PRODUCE SMALL HAIL AND GUSTY WINDS BUT NOT EXPECTING SEVERE THRESHOLDS. WILL ALSO KEEP WORDING OUT OF THE HWO. LOW CLOUDS AND FOG HUNG IN LONG ENOUGH TO LIMIT INSTABILITY FROM CHO TO IAD AND AREAS EAST. A FEW BREAKS IN THE OVERCAST WILL OCCUR FOR A FEW HOURS THIS AFTERNOON BUT THINKING IS THAT DESTABILIZATION WILL BE MINIMAL ACROSS THESE AREAS. HAVE LEFT POPS OUT OF THIS AREA BUT EVENING SHIFT WILL HAVE TO MONITOR TO SEE IF ANYTHING CAN DEVELOP. CONVECTIVE CHANCES SHOULD DIMINISH OVERNIGHT ALTHOUGH A FEW LIGHT SHOWERS/SPRINKLES MAY BE POSSIBLE. BIGGER STORY OVERNIGHT WILL BE THE POTENTIAL FOR FOG DEVELOPMENT. LOW LEVEL MOISTURE SHOULD REMAIN IN PLACE FOR FOG DEVELOPMENT AFTER MIDNIGHT. SOME OF THE FOG COULD BE LOCALLY DENSE...SIMILAR TO THE PATCHY DENSE FOG OF THIS MORNING. HAVE INCLUDED THE POTENTIAL IN THE WX GRIDS. UPPER LOW WILL PULL AWAY TO THE NORTH AND EAST ON WEDNESDAY. FOG AND LOW CLOUDS WILL MIX OUT BY LATE MORNING/MIDDAY WITH A FEW AFTERNOON SHOWERS POSSIBLE ESPECIALLY OVER THE HIGH TERRAIN. AFTERNOON HIGHS FROM THE LOWER TO MIDDLE 70S CAN BE EXPECTED.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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HIGH PRESSURE TO THE NORTH NOSING INTO THE REGION WILL KEEP AN EASTERLY LOW-LEVEL WIND FETCH IN PLACE WEDNESDAY NIGHT INTO THURSDAY. THIS WILL RESULT IN MORE CLOUDS THAN CLEAR SKY THROUGH THE PERIOD...ESPECIALLY EAST OF THE BLUE RIDGE MOUNTAINS. AS THE HIGH PRESSURE MOVES OUT INTO THE NORTHERN ATLANTIC...MID- AND HIGH-LEVEL CLOUDS APPROACHING FROM THE WEST WILL LOWER AND THICKEN IN ADVANCE OF AN APPROACHING TROUGH THURSDAY NIGHT. A COUPLE OF SHOWERS PRECEDING THIS TROUGH COULD APPROACH THE WESTERN SLOPES BY DAYBREAK FRIDAY...BUT THE BULK OF PRECIPITATION IS EXPECTED TO HOLD OFF UNTIL FRIDAY AFTERNOON AND NIGHT.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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A SEASONABLY STRONG UPPER TROUGH AND COLD FRONT WILL MOVE TOWARDS THE MID-ATLANTIC FRIDAY. WIDESPREAD CLOUDS WILL CONTINUE TO LOWER AND THICKEN THROUGH THE DAY...WITH A BAND OF SHOWERS PRECEDING THE FRONT EXPECTING TO MOVE ACROSS THE AREA DURING THE AFTERNOON AND INTO THE OVERNIGHT. MOST AREAS EAST OF THE BLUE RIDGE MOUNTAINS SHOULD REMAIN PREDOMINANTLY DRY DURING THE DAY. MODELS ARE STILL DIVERGENT ON TIMING/STRENGTH OF THE TROUGH WHICH WILL DETERMINE EXACTLY WHO GETS HOW MUCH RAIN AND WHEN. FORCING WITH THE TROUGH IS STRONG BUT THERE IS NOT MUCH INSTABILITY TO WORK WITH...SO WHILE A FEW RUMBLES OF THUNDER CANNOT BE RULED OUT THE CURRENT THINKING IS THAT WIDESPREAD THUNDER IS UNLIKELY. BRIEF HEAVY DOWNPOURS AND PERHAPS GUSTY WINDS IN STRONGER/HEAVIER BANDS OF RAIN COULD BE REALIZED ESPECIALLY IF THE TROUGH ENDS UP BEING ON THE STRONGER SIDE. MODELS ARE IN BETTER AGREEMENT BY LATER SATURDAY AFTER THE FRONT MOVES THROUGH. A MUCH COOLER AND DRIER AIRMASS WILL MOVE INTO THE REGION AND STICK AROUND FOR THE REMAINDER OF THE WEEKEND...WITH TEMPERATURES FALLING TO SEVERAL DEGREES BELOW NORMAL...PERHAPS ISOLATED FREEZING TEMPERATURE READINGS ALONG THE WESTERN RIDGES SATURDAY NIGHT IF WINDS SLACKEN A TAD QUICKER THAN GUIDANCE IS CURRENTLY SUGGESTING. THE NEXT STORM SYSTEM APPROACHES THE AREA FROM THE WEST EARLY NEXT WEEK BUT MODELS ARE HIGHLY DIVERGENT ON WHEN IT AND ITS IMPACTS REACH THE AREA.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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MOSTLY VFR THE REMAINDER OF TODAY...STILL A FEW AREAS SEEING MVFR CIGS BUT THOSE WILL CONTINUE TO MIX OUT. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WILL BE POSSIBLE THE REMAINDER OF THIS AFTERNOON INTO THE EVENING HOURS ESPECIALLY WEST OF THE BLUE RIDGE AND ACROSS THE MASON DIXON LINE. CONFIDENCE IN ANY STORM DIRECTLY IMPACTING A TERMINAL SITE IS LOW...THEREFORE MENTION HAS BEEN LEFT OUT OF THE TAFS. LOW CIGS AND FOG A GOOD BET OVERNIGHT. SOME PATCHY DENSE FOG WILL BE POSSIBLE BUT NOT WIDESPREAD. LOW CIGS AND FOG SHOULD MIX OUT BY LATE MORNING OR MIDDAY WEDNESDAY. CIG AND PSBL VSBY RESTRICTIONS LATE WED NIGHT-THU AM AND AGAIN THU NIGHT INTO FRI AM WITH MOIST ONSHORE FLOW PORTRAYED IN ALL THE GUIDANCE. CLIMO IS FAVORABLE FOR FOG/STRATUS THIS TIME OF THE YEAR SO THAT LENDS TO MODERATE CONFIDENCE. SHWRS/ISO TSTMS IN ONE OR MORE BANDS AHEAD OF A COLD FRONT PSBL W/ GUSTY WINDS FRI-FRI NIGHT. VFR SAT AS WINDS TURN OUT OF THE W OR NW.
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&& .MARINE...
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WINDS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA THE REMAINDER OF TODAY THROUGH THURSDAY. SOLID SCA CONDITIONS LOOKING INCREASINGLY LIKELY LATE THIS WEEK INTO THIS WEEKEND BOTH AHEAD OF /SOUTHERLY FLOW/ AND BEHIND /NORTHWESTERLY FLOW/ A SEASONABLY STRONG COLD FRONT. WINDS/SEAS GRADUALLY ABATE AS THE WEEKEND PROGRESSES.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...KRW NEAR TERM...KRW SHORT TERM...DFH LONG TERM...DFH AVIATION...KRW/DFH MARINE...KRW/DFH

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