Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 211945 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 245 PM EST SUN DEC 21 2014 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH TONIGHT. LOW PRESSURE WILL TRACK UP THE MID-ATLANTIC COAST MONDAY AND TUESDAY. A STRONG COLD FRONT WILL APPROACH THE AREA WEDNESDAY BEFORE PASSING THROUGH WEDNESDAY NIGHT. HIGH PRESSURE WILL BUILD OVERHEAD LATE IN THE WEEK. && .NEAR TERM /THROUGH MONDAY/... HIGH PRESSURE REMAINS OVER THE REGION THIS AFTERNOON AND SUBSIDENCE BEHIND A SHORTWAVE HAS ALLOWED FOR SUNSHINE. HIGH PRESSURE WILL BECOME CENTERED OVER NEW ENGLAND TONIGHT AND THE SURFACE RIDGE AXIS WILL DROP SOUTHWEST THROUGH OUR REGION DURING THIS TIME. POTENT LOW PRESSURE WILL TRACK THROUGH THE PLAINS TONIGHT THROUGH MONDAY. A WARM FRONT WILL EXTEND SOUTHEAST FROM THIS SYSTEM THROUGH THE TENNESSEE VALLEY INTO THE APPALACHIANS WHERE IT WILL BECOME A STATIONARY FRONT THAT CONTINUES TO EXTEND THROUGH THE SOUTHEASTERN CONUS. LOW PRESSURE WILL DEVELOP ALONG THIS BOUNDARY OFF THE SOUTHEAST COAST TONIGHT AND IT IS EXPECTED TO TRACK UP THE MID-ATLANTIC COAST MONDAY. THIS SYSTEM WILL BE WEAK AND MOST OF THE DYNAMICS WILL REMAIN WELL TO OUR WEST...CLOSER TO THE STRONGER LOW OVER THE PLAINS. HOWEVER...WARM AND MOIST AIR FROM THE GULF OF MEXICO AND ATLANTIC OCEAN WILL OVERRUN THE COLDER AND DRIER AIR THAT IS CURRENTLY IN PLACE. THIS WILL CAUSE CLOUDS TO INCREASE OVERNIGHT AND PRECIPITATION IS EXPECTED TO OVERSPREAD AT LEAST PORTIONS OF THE AREA MONDAY MORNING INTO MONDAY AFTERNOON. THERE WILL BE ENOUGH COLD AIR FOR POSSIBLE FROZEN PRECIPITATION MONDAY...ESPECIALLY NORTH AND WEST OF INTERSTATE 95. THE MAIN IMPACT FROM FROZEN PRECIPITATION WOULD BE FROM FREEZING RAIN...ALTHOUGH SNOW AND SLEET MAY MIX WITH PRECIPITATION...ESPECIALLY AT THE ONSET. HOWEVER...THERE IS STILL SOME UNCERTAINTY AS TO HOW FAR NORTH AND WEST THE PRECIPITATION WILL MAKE IT SINCE IT WILL BE RUNNING INTO DRIER AIR. THE HIGHEST CONFIDENCE FOR PRECIPITATION AND SUBFREEZING TEMPERATURES IS ACROSS CENTRAL VIRGINIA. A FREEZING RAIN ADVISORY IS IN EFFECT FOR THESE AREAS MONDAY MORNING. FREEZING RAIN MAY CONTINUE INTO THE AFTERNOON HOURS AS WELL. FOR THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS...CONFIDENCE IS NOT YET HIGH ENOUGH FOR A HEADLINE SINCE TEMPERATURES WILL BE MARGINAL AND IMPACT FROM FROZEN PRECIPITATION IS NOT EXPECTED TO OCCUR UNTIL LATER MONDAY MORNING OR AFTERNOON. PRECIPITATION WILL LIKELY OVERSPREAD THESE AREAS DURING THE MID TO LATE MORNING HOURS MONDAY AND CONTINUE THROUGH MONDAY AFTERNOON. FROZEN PRECIPITATION IS POSSIBLE...ESPECIALLY NORTH AND WEST OF INTERSTATE 95. A FREEZING RAIN ADVISORY MAY BE NEEDED FOR PORTIONS OF THESE AREAS. FOR THE POTOMAC HIGHLANDS...NORTHERN MARYLAND AND EASTERN WEST VIRGINIA. TEMPERATURES WILL BE COLD ENOUGH FOR FROZEN PRECIPITATION...BUT THE NORTHERN AND WESTERN EXTENT OF THE PRECIP IS TOO UNCERTAIN AT THIS TIME TO ISSUE AN ADVISORY. ANY IMPACT FROM FROZEN PRECIPITATION WOULD NOT OCCUR UNTIL MONDAY AFTERNOON. MAX TEMPS MONDAY WILL RANGE FROM THE UPPER 20S AND LOWER 30S ACROSS THE ALLEGHENY AND POTOMAC HIGHLANDS...TO THE MIDDLE 30S NEAR WASHINGTON AND BALTIMORE...TO NEAR 40 IN SOUTHERN MARYLAND. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... LIGHT PRECIPITATION WILL CONTINUE MONDAY NIGHT INTO TUESDAY MORNING. THE BIG QUESTION WILL BE HOW LONG THE CAD WEDGE WILL REMAIN IN PLACE. THERE IS STILL POTENTIAL FOR TEMPERATURES TO REMAIN AT OR BELOW FREEZING MAINLY WEST OF THE BLUE RIDGE LEAVING THE POTENTIAL FOR LIGHT FREEZING RAIN TO CONTINUE. TO THE EAST OF THE BLUE RIDGE AND ACROSS THE METRO AREAS...WARMER AIR WILL LIKELY WIN OUT KEEPING PRECIPITATION IN THE FORM OF RAIN. A BRIEF RESPITE FROM THE PRECIPITATION IS POSSIBLE TUESDAY AFTERNOON/EVENING BEFORE THE NEXT ROUND OF RAINFALL MOVES IN FROM THE WEST LATER TUESDAY NIGHT. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... STRONG COLD FRONT CROSSING THE MID ATLANTIC REGION WEDNESDAY INTO THURSDAY. LIQUID PRECIPITATION SHOULD ACCOMPANY THE FRONT EXCEPT ALONG THE ALLEGHENY FRONT WHERE ARRIVAL OF COLDER AIR WILL CAUSE THE RAIN TO CHANGE OVER TO SNOW BEFORE PRECIPITATION ENDS THURSDAY. PASSAGE OF SHORTWAVE WILL SUPPORT DEVELOPMENT OF A COASTAL LOW LATE SATURDAY AND SUNDAY. PRECIPITATION MAY START AS A WINTRY MIX AT HIGHER ELEVATIONS. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... VFR CONDITIONS THROUGH THIS EVENING. CLOUDS WILL INCREASE OVERNIGHT AND PRECIPITATION WILL OVERSPREAD THE TERMINALS MONDAY FROM SOUTHWEST TO NORTHEAST. FREEZING RAIN IS EXPECTED ACROSS KCHO AND POSSIBLY KMRB AND KIAD. FREEZING RAIN MAY MIX WITH SLEET AND SNOW AT THE ONSET. RAIN IS EXPECTED ACROSS THE REST OF THE TERMINALS. RAIN MAY MIX WITH SLEET AT THE ONSET. CIGS/VSBYS WILL DETERIORATE TO MVFR LEVELS MONDAY WITH POSSIBLE IFR LEVELS. SUB VFR CIGS AND VSBYS EXPECTED MONDAY NIGHT INTO TUESDAY. LIGHT FREEZING RAIN WILL BE POSSIBLE WEST OF THE BLUE RIDGE WITH RAIN TO THE EAST. A PRECIPITATION RESPITE MAY OCCUR TUESDAY AFTERNOON BEFORE RAIN MOVES BACK IN LATER TUESDAY NIGHT. A STRONG COLD FRONT WILL APPROACH THE TERMINALS WEDNESDAY BEFORE PASSING THROUGH WEDNESDAY NIGHT. MORE RAIN AND SUBVFR CONDITIONS ARE EXPECTED. && .MARINE... HIGH PRESSURE WILL REMAIN OVER THE WATERS TONIGHT. LOW PRESSURE WILL TRACK UP THE MID-ATLANTIC COAST MONDAY. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MIDDLE PORTIONS OF THE BAY AND LOWER TIDAL POTOMAC RIVER. WINDS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA MONDAY NIGHT THROUGH TUESDAY NIGHT. A STRONG COLD FRONT WILL APPROACH THE WATERS WEDNESDAY BEFORE PASSING THROUGH WEDNESDAY NIGHT. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR THE WATERS WEDNESDAY AND THURSDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...FREEZING RAIN ADVISORY FROM 6 AM TO NOON EST MONDAY FOR VAZ025- 026-029-036>040-050-051-501>504-507-508. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EST MONDAY FOR ANZ534- 537-543. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...KRW LONG TERM...CEM AVIATION...BJL/KRW MARINE...BJL/KRW

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