Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240730 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 330 AM EDT TUE MAR 24 2015 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD INTO THE MID-ATLANTIC REGION TODAY. THE HIGH WILL MOVE OFF THE COAST WEDNESDAY AND A COLD FRONT IS EXPECTED TO PASS THROUGH LATE THURSDAY INTO THURSDAY NIGHT. CANADIAN HIGH PRESSURE WILL RETURN FOR FRIDAY INTO THE WEEKEND.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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A SHORTWAVE TROUGH IS LOCATED ACROSS THE NRN MID-ATLANTIC EARLY THIS MORNING. HIGH PRESSURE IS LOCATED ACROSS THE EASTERN GREAT LAKES AND NRN NEW ENGLAND. LIGHT SNOW WILL CONTINUE TO TRACK ACROSS THE NORTHERN MID- ATLANTIC THIS MORNING IN RESPONSE TO A WELL-DEFINED SHORTWAVE TROUGH APPARENT ON WATER VAPOR. LACK OF MID-LEVEL CONVERGENCE AND MOISTURE HAS LED TO LIGHT SNOW INTENSITY ACROSS THE POTOMAC HIGHLANDS AND SOUTHERN PA. VSBY HAS DROPPED TO ONLY 5 MILES AT TIMES. SFC TEMPS WILL CONTINUE TO FALL BEFORE SUNRISE BUT ARE MARGINAL...MID TO UPPER 30S. SNOW SHOULD STAY CONFINED TO THE POTOMAC HIGHLANDS...EASTERN PANHANDLE OF WV AND NRN MARYLAND AS IT MOVES FROM WEST TO EAST THIS MORNING. HI-RES GUIDANCE CONTINUES TO WEAKEN ECHOS THROUGH THE MORNING. LESS THAN AN INCH IS EXPECTED ACROSS THE WESTERN SLOPES AND POTOMAC HIGHLANDS THIS MORNING. LITTLE TO NO ACCUMULATION IS EXPECTED ELSEWHERE. THIS TREND WILL CONTINUE THROUGH THE MORNING RUSH HOUR AS THE SHORTWAVE TROUGH EXITS OFF THE NJ COAST. HIGH PRESSURE WILL BUILD BACK INTO THE REGION FROM THE NORTH TODAY. N-NE WINDS WILL KEEP TEMPS BELOW CLIMO AGAIN WITH FCST TEMPS RANGING FROM THE MID TO UPPER 40S TO 50 ACROSS THE PIEDMONT AND CENTRAL FOOTHILLS. CLOUDS ARE EXPECTED TO PERSIST THROUGH MIDDAY BEFORE MOVING OFF THE COAST THIS AFTERNOON. SUNSHINE IS EXPECTED ACROSS MOST AREAS EAST OF THE POTOMAC RIVER. FURTHER SOUTH AND WEST...A WARM FRONT WILL BE APPROACHING FROM THE TN VALLEY THIS AFTERNOON AND EVENING. THIS IS AHEAD OF THE NEXT SYSTEM THAT WILL BE DEEPENING IN THE CENTRAL PLAINS TODAY. OVERRUNNING IS EXPECTED FROM SW-NE TONIGHT AND A CHANCE OF RAIN WILL MOVE INTO THE REGION. TEMPS WILL FALL TONIGHT AND ARE EXPECTED TO GO BELOW FREEZING LATE TONIGHT FOR RIDGE LINES AND NORTH-CENTRAL MARYLAND. RAIN MAY CHANGE TO IP/ZR LATE TONIGHT AND INTO WEDNESDAY MORNING FOR THIS MENTIONED REGION. AT THIS TIME...CONFIDENCE IS LOW THAT ANY PRECIPITATION WILL REACH THIS AREA AS TEMPS APPROACH FREEZING AND THEREFORE WILL CONTINUE TO MONITOR THE LATEST GUIDANCE. HIGH PRESSURE WILL BE WEDGED ACROSS THE REGION WEDNESDAY WHILE A 40- 50KT JET AT 3-5K FEET TRANSPORTS WARM AIR INTO THE REGION ALOFT. THE WEDGE OF HIGH PRESSURE IS EXPECTED TO HALT TEMPS FROM RISING EAST OF THE BLUE RIDGE WEDNESDAY. AREAS ACROSS THE HIGHLANDS AND SHENANDOAH VALLEY WILL LIKELY SEE 55-65 DEGREES WHILE IAD-DCA-BWI WILL LIKELY BE IN THE 40S. SOME UNCERTAINTY EXISTS IN THIS TEMP FORECAST AS SOUTHERLY WINDS COULD POTENTIALLY MIX DOWN SOME WARMER AIR.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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ON WEDNESDAY NIGHT...WELL-ORGANIZED LOW PRESSURE WILL QUICKLY MOVE FROM THE MISISSIPPI VALLEY INTO THE LOWER GREAT LAKES...WHILE HIGH PRESSURE PERSISTS OFFSHORE. MOISTURE AND WARM AIR WILL ADVECT INTO THE REGION...SUCH THAT TEMPERATURES WILL NOT DROP MUCH OVERNIGHT. THE INCREASE IN MOISTURE AND LIFT FROM A MID-LEVEL JET STREAK WILL PROMOTE POTENTIAL FOR A FEW SHOWERS. PRESSURE GRADIENT BETWEEN THE OFFSHORE HIGH AND THE LOW TO OUR WEST WILL KEEP A STEADY SOUTH BREEZE OVER THE REGION. LOWS GENERALLY IN THE 40S EXPECTED. COLD FRONT STILL ON TRACK TO MOVE THROUGH THE FORECAST AREA THURSDAY AFTERNOON OR EVENING. BEFORE THE FROPA...TEMPERATURES WILL SURGE INTO THE UPPER 60S AND LOWER 70S...WITH MID 70S POSSIBLE OVER PORTIONS OF THE VIRGINIA PIEDMONT. A STRONG 850MB JET WILL MOVE THROUGH THE AREA AS WELL...WITH POTENTIAL FOR GUSTY WINDS OUTSIDE OF ANY CONVECTIVE ACTIVITY. THE COLD FRONT WILL BE ACCOMPANIED BY STRONG LIFT AND FAVORABLE JET DYNAMICS...SUPPORTING SHOWERS AND POTENTIALLY A FEW THUNDERSTORMS. TEMPERATURES DROP QUIKCLY THURSDAY NIGHT BEHIND THE COLD FRONT...BUT RAIN POTENTIAL CONTINUES WITH A NEARLY SATURATED VERTICAL COLUMN ON BUFKIT SOUNDINGS AND CONTINUED WARM ADVECTION ALOFT AHEAD OF AN UPPER TROUGH. LOWS IN THE 40S ARE EXPECTED...SO ANY PRECIPITATION SHOULD REMAIN LIQUID. GUSTY WINDS WILL BE POSSIBLE AGAIN THURSDAY NIGHT.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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UPSLOPE RAIN OR SNOW POSSIBLE OVER THE POTOMAC HIGHLANDS IN THE WAKE OF THE COLD FRONT. AN UPPER TROUGH WILL PIVOT INTO THE APPALACHIANS AS WELL...BRINGING POTENTIAL FOR A FEW SHOWERS OVER PORTIONS OF THE FORECAST AREA. HIGH PRESSURE BUILDS IN THROUGH THE WEEKEND...WITH BELOW NORMAL TEMPERATURES. THE NEXT COLD FRONT MOVES THROUGH THE REGION MONDAY.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/...
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VFR CONDITIONS EXPECTED TODAY. -SN IS POSSIBLE AT MRB- IAD-DCA-BWI-MTN THIS MORNING BUT VSBYS SHOULD STAY ABOVE MVFR. HIGH PRESSURE BUILDS INTO THE REGION TODAY AND WEDNESDAY. -RA MAY MOVE FROM S-N TONIGHT AND WEDNESDAY. CIGS WILL LIKELY BECOME SUB-VFR LATE TONIGHT AND INTO WEDNESDAY AT CHO. FURTHER NORTH...LOWER CONFIDENCE EXISTS. PERIODIC SUB-VFR POSSIBLE WEDNESDAY NIGHT. SLY WINDS AROUND 10KT. A POTENT COLD FRONT WILL MOVE THROUGH THURSDAY AFTERNOON OR EVENING...WITH SHRA LIKELY AND A PSBL TSTM. S-SW WINDS MAY BE GUSTY THURSDAY AFTERNOON AND EVENING. WINDS SHIFT TO THE NW THURSDAY NIGHT...WITH POTENTIAL GUSTS. VFR LIKELY FRIDAY WITH NW WINDS...ALTHOUGH A SHOWER CANNOT BE RULED OUT. VFR WITH HIGH PRESSURE OVER THE WEEKEND.
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&& .MARINE...
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HIGH PRESSURE IS EXPECTED TODAY AND TONIGHT ACROSS THE WATERS. WINDS WILL REMAIN BELOW SCA DURING THIS TIME. SOUTHERLY WINDS WILL INCREASE ON THE WATERS WEDNESDAY. AT THIS TIME... CONFIDENCE IS LOW WHETHER A SCA WILL BE NEEDED WEDNESDAY DUE TO THE FULL MIXING POTENTIAL DURING THE DAY. SCA WILL LIKELY BE NEEDED THURSDAY WITH GUSTY SOUTHERLY WINDS AHEAD OF A COLD FRONT. SHOWERS AND A PSBL TSTM THURSDAY AFTN OR EVENING WITH THE COLD FRONT. GALES ARE ALSO POSSIBLE BEHIND THE COLD FRONT THURSDAY NIGHT. SMALL CRAFT CONDITIONS POSSIBLE AGAIN FRIDAY AND SATURDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...HAS NEAR TERM...HAS SHORT TERM...KS LONG TERM...KS AVIATION...HAS/KS MARINE...HAS/KS

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