Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 021524 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1024 AM EST MON MAR 2 2015 .SYNOPSIS...
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A COLD FRONT WILL CROSS THE MIDDLE ATLANTIC REGION TODAY. HIGH PRESSURE THEN WILL BUILD IN THROUGH THE FIRST PART OF TUESDAY. A WARM FRONT WILL PUSH THROUGH THE AREA TUESDAY NIGHT. A STRONG COLD FRONT WILL APPROACH THE REGION LATE WEDNESDAY FOLLOWED BY COLD HIGH PRESSURE FOR THURSDAY INTO THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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COLD FRONT HAS PUSHED THROUGH MUCH OF THE FORECAST AREA AS OF 15Z. WINDS HAVE BACKED TO THE NORTHWEST WITH DECENT MIXING ONGOING ACROSS THE FORECAST AREA. EARLIER PATCHY DENSE FOG ACROSS THE METRO AREAS...CENTRAL VA AND SOUTHERN MD HAS MIXED OUT AND SKIES WILL CONTINUE TO SHOW A CLEARING TREND THE REMAINDER OF THIS MORNING AND INTO THE AFTERNOON HOURS. OUT WEST...CLOUDS WILL REMAIN IN PLACE DUE TO UPSLOPE COMPONENT WITH SOME SCATTERED SNOW SHOWERS POSSIBLE OVER THE WESTERN SLOPES OF THE ALLEGHENY FRONT. TEMPERATURES ARE A BIT OF A CHALLENGE TODAY. COLD FRONT HAS CROSSED THE BULK OF THE REGION BUT NORTHWEST WIND COMPONENT WILL AID IN MIXING AND A DOWNSLOPE DIRECTION. TEMPERATURES MAY WARM A FEW DEGREES INTO THIS AFTERNOON BEFORE THEY TREND DOWNWARD LATER IN THE DAY. NORTHWEST WINDS WILL REMAIN ON THE BREEZY SIDE WITH SPEEDS GENERALLY IN THE 10-20 MPH RANGE WITH A FEW 25-30 MPH GUSTS POSSIBLE BEHIND THE FRO-PA. WINDS WILL DROP OFF THIS EVENING AND SO WILL THE TEMPERATURES. OVERNIGHT LOWS ARE EXPECTED TO DROP OFF INTO THE LOW 20S IN MOST LOCATIONS EXCEPT A FEW TEENS OUT WEST.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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CLOUDS WILL INCREASE FROM THE SOUTHWEST TOWARDS TUESDAY MORNING AS THE NEXT SYSTEMS APPROACHES THE REGION. HIGH PRESSURE WILL BE LOCKED IN PLACE AT THE SURFACE WHILE WARM ADVECTION HEADS TOWARDS THE MID- ATLANTIC. SIMILAR TO SUNDAY...WARM AIR ADVECTION WILL LEAD TO PRECIPITATION TO MOVE INTO THE REGION FROM THE SW. PRECIPITATION IS EXPECTED TO BEGIN AS SNOW BEFORE QUICKLY CHANGING TO IP/FZRA BY TUESDAY AFTERNOON. FCST MAX TEMPS FOR TUESDAY RANGE FROM THE LOW 30S IN NE MD TO THE MID 30S EAST OF THE BLUE RIDGE. FURTHER WEST...TEMPS SHOULD RISE ABOVE FREEZING IN THE SHENANDOAH VALLEY AND HIGHER ELEVATIONS. LESS THAN A TENTH INCH OF ICE IS EXPECTED TUESDAY AFTERNOON FOR AREAS EAST OF THE BLUE RIDGE. CONFIDENCE IS LOW FOR AREAS ACROSS THE PIEDMONT AND SOUTHERN MD WHERE TEMPS MAY REACH THE MID 30S. THE MIDDLE PORTION OF THE WEEK WILL BE VERY ACTIVE WITH SUBSTANTIAL SWINGS IN THE WEATHER. WHAT HAPPENS TUESDAY EVENING MAY BE DEPENDENT ON HOW MUCH TEMPERATURES CAN WARM ON TUESDAY. STRONG WAA WILL BE TAKING PLACE ALOFT...BUT AS USUAL THE QUESTION IS HOW MUCH TRANSLATES TO THE SFC...ESPECIALLY IN AREAS WHERE THE COLDER AIR IS WEDGED IN. BY TUESDAY EVENING THIS MAY ONLY BE IN THE MOST FAVORED AREAS ADJACENT TO THE NORTHERN BLUE RIDGE AND ACROSS NORTHERN MD. LEFT RA-OR-FZRA WORDING IN THESE AREAS FOR THE EVENING. CURRENT FORECAST CALLS FOR WARM AIR TO WIN OUT WITH RISING TEMPERATURES OVERNIGHT...BUT THIS IS FAR FROM CERTAIN IN THE AREAS MENTIONED ABOVE. ON THE OTHER HAND...THE HIGHER ELEVATIONS COULD BE NEAR 50F OR GREATER BY DAYBREAK.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AREA STILL FORECAST TO REMAIN IN THE WARM SECTOR ON WED WITH HIGHS INTO THE 50S EXCEPT N-CNTL/NE MD. SHOWERS WILL BE LIKELY THROUGHOUT THE DAY IN A BROAD AREA OF MOIST ASCENT. HOWEVER IT LOOKS LIKE THE GREATER MOISTURE MAY REMAIN SW OF THE AREA THROUGH THIS TIME...WHICH WOULD REDUCE THE THREAT FOR ANY FLOODING. WED NIGHT/THU FORECAST IS QUITE UNCERTAIN AS A COLD FRONT SLOWLY SLIPS THROUGH THE AREA. IT WILL BE NEARLY PARALLEL TO A STRONG UPPER JET...DENOTING THE TIGHT LOW LEVEL BAROCLINIC ZONE. AT LEAST ONE WAVE OF LOW PRESSURE IS FORECAST TO TRACK ALONG THE FRONT...WHICH COULD OCCUR AFTER COLDER AIR BEGINS TO PUSH INTO THE AREA. HAVE BROADBRUSHED RA/SN WORDING BASED ON FORECAST TEMPS. A LOT OF MOISTURE WILL BE IN PLAY IN THE FRONTAL ZONE...WHICH COULD PRESENT ACCUMULATING SNOW. AGREE WITH WPC GUIDANCE THAT THE BEST CHANCE FOR SNOW ACCUMULATIONS WILL BE N/W OF DC...WITH THE HIGHEST AMOUNTS IN THE WV MOUNTAINS. CERTAINLY A SITUATION TO MONITOR. ARCTIC HIGH PRESSURE WORKS IN FULLY BY THU NIGHT...WITH LOWS DROPPING INTO THE TEENS AND SINGLE DIGITS. THE HIGH WILL SLOWLY MOVE EAST ACROSS THE AREA THROUGH SATURDAY. EXPECT GRADUALLY MODERATING TEMPERATURES...PERHAPS PUSHING CLIMO BY SATURDAY AND SUNDAY. A MOISTURE STARVED COLD FRONT MAY APPROACH LATE IN THE WEEKEND. && .AVIATION /15Z MONDAY THROUGH FRIDAY/...
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VFR CONDITIONS EXPECTED AT THE TERMINAL SITES INTO TONIGHT. NORTHWEST WINDS WILL BE GUSTY TODAY WITH SPEEDS IN THE 10-20 KT RANGE WITH HIGHER GUSTS UP TO 25 KTS POSSIBLE BEHIDN THE FRONTAL PASSAGE. SCATTERED UPSLOPE SNOW SHOWERS WILL BE POSSIBLE OVER THE WESTERN SLOPES OF THE ALLEGHENY FRONT THROUGH THIS AFTERNOON. WINDS WILL SUBSIDE TONIGHT AND VFR CONDITIONS WILL CONTINUE THROUGH TONIGHT. HIGH PRESSURE BUILDS INTO THE REGION TUESDAY BUT MOISTURE WILL MOVE IN FROM THE SW. -SNPL BECOMING FZRA WILL IMPACT THE TERMINALS BY TUESDAY AFTERNOON. BEST CHANCE FOR ICE ACCUMULATION WILL BE AT BWI-MTN. VSBY/CIG REDUCTIONS WILL CONTINUE TUESDAY NIGHT THROUGH WEDNESDAY WITH RAIN AT TIMES. GUSTY SOUTHERLY WINDS ALSO EXPECTED ON WEDNESDAY. RAIN MAY CHANGE TO SNOW FOR PORTIONS OF THE AREA WEDNESDAY NIGHT-THURSDAY...WHICH WOULD LEAD TO SUB-VFR CONDITIONS.
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&& .MARINE...
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SCA CONDITIONS ARE EXPECTED ON THE WATERS AS A COLD FRONT SWEEPS THROUGH. WIND GUSTS IN THE 18-25 KT RANGE WILL BE COMMON THROUGH EARLY EVENING BEFORE DIMINISHING. SCA CONDITIONS WILL BE POSSIBLE TUESDAY NIGHT INTO WEDNESDAY AHEAD OF AN APPROACHING COLD FRONT...AND AGAIN LATE WEDNESDAY NIGHT INTO THURSDAY AS COLD AIR PUSHES IN BEHIND THE FRONT.
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&& .HYDROLOGY... WE HAVE BEEN ADVERTISING THE POTENTIAL OF MIDWEEK FLOODING IN THE HAZARDOUS WEATHER OUTLOOK. LIQUID PRECIP FCST FROM WPC PUTS MUCH OF THE FCST AREA IN A MINIMA FOR AMOUNTS...AROUND AN INCH OR LESS IN MANY AREAS. WITH TEMPERATURES EXPECTED TO RISE INTO THE 50S ON WEDNESDAY...THERE WILL BE SOME...POSSIBLY A LOT OF...MELTING OF THE EXISTING SNOWPACK...WHICH COMPUTER MODELS AND OBSERVATIONS INDICATE CONTAINS ANYWHERE FROM 3/4 INCH TO 2 INCHES OF SNOW WATER EQUIVALENT. THIS COMBINATION MAY LEAD TO MINOR FLOODING AS THE RAIN FALLS ON WEDNESDAY. ALTHOUGH RIVER ICE IS NOT ESPECIALLY THICK...IT WILL HAVE TO BE MONITORED FOR POTENTIAL ROLE IN AFFECTING RUNOFF. ALSO...PLOWED SNOW IS LIKELY COVERING SOME OF THE DRAINS OUT THERE...WHICH COULD CAUSE MORE POOR DRAINAGE FLOODING THAN WOULD OTHERWISE USUALLY BE EXPECTED. WORTH NOTING...CURRENT FORECAST RAIN TOTALS ARE ON THE LOWER SIDE OF THE ENSEMBLE SUITES OF THE GEFS AND SREF. PLEASE CONTINUE TO MONITOR THE FORECAST FOR UPDATES AS THE EVENT GETS CLOSER. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ530>543.
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&& $$ SYNOPSIS...KRW NEAR TERM...KRW SHORT TERM...ADS/HAS LONG TERM...ADS AVIATION...ADS/KRW MARINE...ADS/KRW HYDROLOGY...JE

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