Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 271958
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
258 PM EST FRI FEB 27 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVERHEAD THROUGH SATURDAY. THE HIGH WILL
MOVE OFF THE COAST SUNDAY AND ANOTHER COLD FRONT WILL PASS THROUGH
THE AREA SUNDAY NIGHT. A WARM FRONT AND LOW PRESSURE WILL CROSS
THE AREA TUESDAY AND WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE WILL APPROACH FROM THE OHIO VALLEY BEHIND THE COLD
FRONT LATE THIS AFTERNOON. A NORTHWEST FLOW AHEAD OF THE HIGH
WILL USHER IN COLD CONDITIONS.

HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT...BRINGING DRY AND COLD
CONDITIONS. HIGH CLOUDS WILL INCREASE AS AN UPPER-LEVEL
DISTURBANCE MOVES INTO THE AREA FROM THE SOUTHWEST. HOWEVER...THE
CLOUD DECK SHOULD BE THIN ENOUGH TO ALLOW FOR RADIATIONAL COOLING.
THEREFORE...THE MIN TEMP FORECAST LEANS TOWARD OR EVEN A LITTLE
BELOW THE COLDEST GUIDANCE. MIN TEMPS ARE FORECAST TO RANGE FROM
BELOW ZERO IN THE ALLEGHENY HIGHLANDS...TO THE SINGLE DIGITS AND
LOWER TEENS ACROSS MOST OTHER LOCATIONS...TO THE MID AND UPPER
TEENS IN WASHINGTON AND BALTIMORE.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
HIGH PRESSURE WILL REMAIN OVERHEAD SATURDAY WHILE SHORTWAVE ENERGY
PASSES THROUGH IN THE SOUTHWEST FLOW ALOFT. A BKN DECK OF HIGH AND
MID-LEVEL CLOUDS ARE EXPECTED DUE TO THE SHORTWAVE ENERGY...BUT IT
WILL REMAIN DRY. THE HIGH WILL CONTINUE TO BRING COLD CONDITIONS
TO THE AREA. MAX TEMPS WILL RANGE FROM THE LOWER 20S IN THE
MOUNTAINS TO THE MID AND UPPER 20S ACROSS MOST OTHER LOCATIONS.

HIGH PRESSURE WILL SHIFT EAST OFF THE MIDDLE ATLANTIC COAST SATURDAY
NIGHT. WINDS WILL SHIFT AROUND TO THE EAST AND SOUTHEAST OVERNIGHT
WHICH WILL HELP DRAW LOW LEVEL MOISTURE INTO THE FORECAST AREA. MOST
OF SATURDAY NIGHT WILL LIKELY REMAIN DRY...EXCEPT OVER THE WESTERN
SLOPES OF THE ALLEGHENY FRONT WHERE SOME SNOW SHOWER ACTIVITY COULD
DEVELOP. CLOUDS WILL BE ON THE INCREASE FROM WEST TO EAST BUT
OVERNIGHT LOW TEMPERATURES WILL BE COLD WITH READINGS FALLING BACK
TO THE TEENS TO LOWER 20S AREAWIDE.

CHALLENGING FORECAST FOR SUNDAY INTO MONDAY. LOW PRESSURE WILL
APPROACH FROM THE WEST AND WARMER AIR WILL OVERRUN A COLDER
AIRMASS LEADING TO PRECIPITATION DEVELOPING FROM WEST TO EAST
ACROSS THE MIDDLE ATLANTIC REGION. THE 12Z NAM IS MORE BULLISH
WITH PRECIPITATION AND KEEPS THE COLD AIR IN PLACE WITH
SUBFREEZING TEMPS ACROSS MUCH OF THE REGION INTO SUNDAY NIGHT. THE
GFS AND ECMWF CONTINUE TO SHOW THE PRECIPITATION COMING IN LATER
AND WITH WARMER TEMPERATURES. THIS MAKES FOR A PROBLEMATIC
FORECAST WITH REGARD TO P- TYPE AND TIMING. COLD AIR TYPICALLY
HOLDS IN LONGER THAN MODELS INDICATE AND HAVE THUS GONE WITH A
CHANCE FOR SNOW TO START ON SUNDAY THEN GRADUALLY CHANGE THE
PRECIPITATION OVER TO S/ZR/IP FROM SOUTH TO NORTH WITH PRECIP
CHANGING TO RAIN OVER CENTRAL AND SOUTHERN PORTIONS OF THE
FORECAST AREA INCLUDING DC/NOVA AND POINTS SOUTH. THIS REMAINS A
HIGHLY UNCERTAIN FORECAST AND DETAILS WILL NEED TO BE REFINED OVER
THE NEXT COUPLE OF DAYS.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
UPPER LEVEL RIDGE BUILDING OVER REGION DURING FIRST HALF OF
PERIOD WILL MOVE OFFSHORE WEDNESDAY NIGHT. WEAK PVA WILL CROSS
REGION. UPPER LEVEL TROF WILL CROSS REGION THURSDAY. STRONGEST OF
ENERGY WILL STAY NORTH OF AREA. FLOW BECOMING ZONAL FRIDAY.

SURFACE HIGH WILL BUILD OVER THE AREA MONDAY BEFORE MOVING
OFFSHORE TUESDAY. MOISTURE AND WARM AIR WILL ADVECT ACROSS THE
AREA FROM SOUTHWEST TO NORTHEAST AS THE HIGH MOVES OFFSHORE.
THERMAL PROFILES INDICATE THAT PRECIPITATION MAY START OFF AS A
WINTRY MIX BEFORE WARMER AIR WORKS ITS WAY INTO THE AREA...CAUSING
PRECIPITATION TO CHANGE TO RAIN TUESDAY NIGHT. ALL RAIN WILL FALL
WEDNESDAY AND IT MAY TURN OUT QUITE WARM AS SOUTHERLY WINDS USHER
IN WARMER AIR FROM THE SOUTH. THE COLD FRONT ASSOCIATED WITH THE
LOW WILL PASS THROUGH WEDNESDAY NIGHT INTO THURSDAY. PRECIPITATION
MAY END AS A PERIOD OF SNOW DURING THIS TIME...BUT DETAILS ARE
UNCERTAIN. HIGH PRESSURE WILL BUILD TOWARD THE AREA LATE NEXT
WEEK.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
VFR CONDITIONS ARE EXPECTED THROUGH SATURDAY. NORTHWEST WINDS WILL
BECOME LIGHT AND VARIABLE TOWARD SUNSET. LIGHT WINDS WILL CONTINUE
THROUGH SATURDAY.

VFR CONDITIONS EXPECTED SATURDAY NIGHT INTO THE FIRST
PART OF SUNDAY FOLLOWED BY MVFR TO IFR CONDITIONS SUNDAY LATE
MORNING INTO THE FIRST PART OF MONDAY. A PERIOD OF SNOW/ZR/IP WILL
BE POSSIBLE AT ALL THE TERMINAL SITES...ESPECIALLY KBWI/KMTN/KMRB
AND KIAD. IMPROVING CONDITIONS WILL FOLLOW FROM WEST TO EAST LATER
MONDAY. LOW PRESSURE AND ITS ASSOCIATED COLD FRONT WILL IMPACT THE
TERMINALS LATER TUESDAY AND WEDNESDAY.

&&

.MARINE...
HIGH PRESSURE WILL BUILD OVER THE WATERS THROUGH SATURDAY. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE WATERS THIS
AFTERNOON...BUT IT WILL BE MARGINAL ACROSS THE UPPER TIDAL POTOMAC
RIVER AND NORTHERN PORTION OF THE BAY. THE SMALL CRAFT ADVISORY
CONTINUES TONIGHT FOR THE MARYLAND CHESAPEAKE BAY SOUTH OF POOLES
ISLAND AND THE LOWER TIDAL POTOMAC RIVER. NORTHERLY WINDS OVER THE
RELATIVELY WARMER WATERS WILL INCREASE MIXING ACROSS THESE AREAS.

WINDS WILL BE LIGHT SATURDAY AS HIGH PRESSURE BUILDS OVERHEAD.
WINDS ARE EXPECTED TO REMAIN BELOW SCA LEVELS SATURDAY NIGHT
THROUGH MONDAY. WINTRY PRECIPITATION WILL CAUSE REDUCED
VISIBILITIES ON THE WATERS LATER SUNDAY INTO MONDAY. LOW PRESSURE
AND ITS ASSOCIATED COLD FRONT WILL IMPACT THE WATERS DURING THE
MIDDLE PORTION OF NEXT WEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST SATURDAY FOR ANZ531>534-
     537-539>541-543.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ530-
     535-536-538-542.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL/KRW
LONG TERM...CEM
AVIATION...BJL/KRW
MARINE...BJL/KRW


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