Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 160135 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 935 PM EDT WED APR 15 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER THE REGION TONIGHT BEFORE MOVING OFF THE COAST THURSDAY. A WEAK COLD FRONT WILL PASS THROUGH LATE FRIDAY AND HIGH PRESSURE WILL RETURN FOR SATURDAY AS THE BOUNDARY STALLS TO OUR SOUTH. THE BOUNDARY WILL RETURN NORTH AS A WARM FRONT SUNDAY INTO MONDAY BEFORE A COLD FRONT SWINGS THROUGH MONDAY NIGHT. && .NEAR TERM /THROUGH THURSDAY/... A FAIRLY STRONG SFC HIGH HOLDING ITS GROUND...AT LEAST ON THE SRN FLANK AND PREVENTING PRECIP FROM MARCHING NWD INTO THE CWA. A SFC HIGH AROUND 1030MB CONTINUES TO DRIFT OVER SE CANADA PUSHING COOLER/DRIER AIR AT THE LOW LEVELS DOWN INTO THE NRN EDGE OF A REGIONAL-SIZED UPPER DISTURBANCE OVER THE DEEP SOUTH. IN THE BIGGER PICTURE...A CLOSED UPPER LOW IS SWINGING OVER THE ROCKIES/INNER MTN WEST AND A WEAK UPPER TROUGH IS BEING TIMIDLY GUIDED UP ACROSS THE SRN MS VLY. SOME DISORGANIZED BATCHES OF PRECIP ARE SLIDING OVER THE SRN ATLC STATES...DISSIPATING THE NRN END OF THE SHOWERS ACROSS THE VA/NC BORDER. PLENTY OF RESIDUAL DEBRIS CIRRUS IS BEING PUSHED UP OUR WAY AND WILL CONTINUE TO DO SO...EVEN AS THE HIGH CHEWS AWAY AT THIS MOISTURE FROM THE NORTH. OVERNIGHT LOWS WILL BE MODERATED FOR ANOTHER NIGHT...A COUPLE/FEW DEG COOLER THAN LAST NIGHT BUT STILL RIGHT AROUND AVG FOR MID-APR. MODELS CONTINUE TO DISSIPATE THE OVERHEAD CIRRUS AT LEAST ENOUGH TO MOVE INTO A LESSER CATEGORY...LIKE MOSTLY/PARTLY CLOUDY. NOT MUCH RADIATIONAL COOLING ANTICIPATED EXCEPT OVER THE NERN SECTIONS OF THE AREA...FURTHER AWAY FROM THE INCOMING PRECIP/CLOUDS AND CLOSER TO THE DRY HIGH PRESSURE. THIS WILL CONTINUE TO BE THE STORY HEADING INTO WED...AS THE HIGH ROLLS OFF THE NEW ENGLAND COAST AND KEEPS THE DRY AIR CHEWING INTO THE INCOMING CLOUDS/PRECIP - JUST AT A DIFFERENT ANGLE. THE ERN HALF OF THE CWA WILL REMAIN DRIER LONGER...AS THE HIGH PRES LOSES ITS INFLUENCE ON THE HIGHER TERRAIN OF THE APLCNS LATER IN THE AFTN. EVEN W/ RADAR ECHOES OF PRECIP SLIDING EWD...MUCH OF THIS IN NOT EXPECTED TO REACH THE SFC UNTIL LATER IN THE AFTN/EVE OVER THE ERN HALF OF THE CWA. ANY RAINFALL AMOUNTS WILL BE LIGHT DUE TO WEAK FORCING. MAX TEMPS WILL RANGE FROM THE 50S IN THE CENTRAL SHENANDOAH VALLEY TO THE UPPER 60S/NEAR 70 NEAR WASHINGTON AND BALTIMORE WHERE BREAKS OF SUNSHINE WILL HOLD ON LONGER. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... HIGH PRESSURE DRIFTS EAST FROM THE MID-ATLANTIC COAST TO BERMUDA THURSDAY NIGHT THROUGH FRIDAY. A CAD WEDGE WITH ONSHORE FLOW EXPECTED ON THURSDAY SHOULD GENERALLY SHIFT TO SLY FLOW BY THURSDAY EVENING. THIS IS NOT A BREAK OF THE WEDGE...AS WIDE SCALE ASCENT IN THE RETURN FLOW CONTINUES TO BRING CLOUDS AND INCREASING MOISTURE. BROUGHT INCREASING CHANCES/LIKELIES FOR SHOWERS TO THE AREA THURSDAY NIGHT INTO FRIDAY AHEAD OF A WEAK COLD FRONT CROSSING THE AREA LATE FRIDAY. AN UPR SHORT WAVE TROUGH CROSSES THE NRN MID- ATLANTIC THURSDAY NIGHT. THAT ALLOWED FOCUS FOR TWO INSTANCES OF LIKELY POPS IN THE SHORT TERM...THURSDAY NIGHT PIEDMONT AND WEST AND THEN FRIDAY AFTERNOON AS THE WEAK COLD FRONT CROSSES AN AREA THAT HAS MOISTENED FOR THE PAST DAY DURING PEAK HEATING. ALL PRECIP IN THIS TIME LOOKS LIGHT WITH LITTLE INSTABILITY. POPS QUICKLY DROP OFF FRIDAY EVENING AS HIGH PRESSURE BUILDS IN FROM THE MIDWEST. TEMPERATURES A LITTLE ABOVE NORMAL THURSDAY NIGHT THROUGH FRIDAY NIGHT WITH CLOUDS AND SLY FLOW...MINS GENERALLY LOW TO MID 50S AND MAX TEMPS FRIDAY IN THE LOW 70S. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... MODEL GUIDANCE IS FINALLY COMING INTO BETTER AGREEMENT FOR THE WEEKEND. INCREASING CONFIDENCE IN HIGH PRESSURE NOSING OVER THE AREA ON SATURDAY...LEADING TO MINIMAL CHANCES OF PRECIPITATION AND TEMPERATURES NEAR TO A FEW DEGREES ABOVE NORMAL. A LARGE AND SLOW-MOVING TROUGH WILL SET ITS SIGHTS ON THE AREA DURING THE SECOND HALF OF THE WEEKEND AND INTO EARLY NEXT WEEK. IF PARTS OF THE AREA CAN WARM SECTOR ON MONDAY THEN THERE COULD BE SOME THUNDERSTORMS...AND INCLUDED A SLIGHT CHANCE FOR THIS IN CLIMATOLOGICALLY-FAVORED AREAS /MAINLY SOUTHERN HALF OF THE CWA/. A LARGE UPPER-LEVEL LOW WILL STALL IN THE VICINITY OF THE NORTHERN GREAT LAKES NEXT TUESDAY-WEDNESDAY...WITH LARGE SCALE NORTHWEST FLOW BRINGING IN A SEASONABLY MILD AIRMASS DURING THE MIDDLE PART OF NEXT WEEK. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... VFR CONDITIONS THROUGH THURSDAY. WINDS WILL TURN TO THE SOUTHEAST THURSDAY WITH GUSTS AROUND 15 TO 20 KNOTS POSSIBLE IN THE AFTN. LOW CLOUDS DEVELOP AS RETURN FLOW FROM HIGH PRESSURE OFF THE COAST BRINGS IN MOISTURE TO THE AREA. SOME LIGHT RAIN FOR THE TERMINALS THURSDAY NIGHT (MAINLY WEST FROM DC METROS) AND AGAIN FRIDAY AFTERNOON AS A WEAK COLD FRONT CROSSES THE REGION. VFR RETURNS FRIDAY NIGHT AS HIGH PRESSURE BUILDS FROM THE WEST. WINDS GENERALLY LESS THAN 10 KT THURSDAY THROUGH FRIDAY NIGHT. LIGHT FLOW GENERALLY NLY 10 KNOTS OR LESS SAT-SAT NIGHT W/ MAINLY VFR LIKELY. FLOW BECOMES ELY AROUND 10 KNOTS SUN-MON W/ SUB-VFR INCREASINGLY LIKELY IN -RA. && .MARINE... HIGH PRESSURE WILL REMAIN OVER THE WATERS THROUGH TONIGHT BEFORE MOVING OFF THE COAST THURSDAY. NORTH TO NORTHEAST WINDS ARE EXPECTED THROUGH TONIGHT...BUT WIND SHOULD REMAIN BELOW SCA CRITERIA. WINDS WILL TURN TO THE SOUTHEAST THURSDAY. AN DEEPER MIXING LAYER WILL CAUSE WINDS TO GUST CLOSE TO 20 KNOTS LATE IN THE MORNING AND AFTERNOON. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE WATERS. SLY FLOW THURSDAY NIGHT THROUGH FRIDAY AS HIGH PRESSURE DRIFTS FROM THE MID-ATLANTIC COAST AND A WEAK COLD FRONT APPROACHES. 10 TO 15 KT SLY FLOW EXPECTED...COULD BE SOME LOCAL CHANNELING...SO WILL HAVE TO WATCH FOR 20 KT GUSTS AND REQUISITE STATEMENT OR ADVISORIES. FLOW SHOULD BE GENERALLY LIGHT AS A RIDGE OF HIGH PRESSURE MOVES OVER THE WATERS SATURDAY. WINDS BECOME EASTERLY AND INCREASE SUNDAY INTO MONDAY WITH SMALL CRAFT CONDITIONS BECOMING INCREASINGLY LIKELY DURING THIS TIME. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EDT THURSDAY FOR ANZ530>543. && $$ UPDATE...GMS PREV DISCUSSION...BJL/BAJ/DFH

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