Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 181703 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 103 PM EDT FRI APR 18 2014 .SYNOPSIS... HIGH PRESSURE WILL REMAIN ACROSS THE NORTHEAST U.S. THROUGH SATURDAY...WHILE AN AREA OF LOW PRESSURE DEVELOPS AND MOVES SLOWLY EAST THROUGH THE SOUTHEAST STATES...MOVING OFF THE SOUTHEAST U.S. COAST MONDAY. THIS SYSTEM WILL BRING LIGHT RAIN TO THE SOUTHERN PORTIONS OF THE FORECAST AREA TONIGHT AND SATURDAY. AN UPPER TROUGH AND ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION FROM THE WEST EARLY NEXT WEEK WITH THE NEXT CHANCE FOR SHOWERS AND POSSIBLY THUNDERSTORMS. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1025 AM EDT FRIDAY... THICK CANOPY OF HIGH CLOUDS CONTINUES TO SHEAR NE ACROSS MUCH OF THE REGION THIS MORNING WITH SOME LINGERING LOW CLOUDS ALONG/EAST OF THE BLUE RIDGE UNDER THE WEDGE. PRECIP REACHING THE GROUND WITH THE STRONG SE UPPER LOW REMAINS WELL TO THE SOUTH ATTM WITH MOST SHORT TERM MODELS AND THE LATEST NAM KEEPING MOST OUT OF THE CWA UNTIL THIS EVENING. THEREFORE GIVEN DRY MID LEVELS OFF MORNING SOUNDINGS TRIMMED BACK POPS OVER THE FAR SOUTH THIS AFTERNOON WHILE KEEPING EXTENSIVE CLOUD COVER GIVEN GOING ADVECTION OF MOISTURE FROM THE SOUTH. THIS ALONG WITH AN OVERALL EAST/NE TRAJECTORY WILL LIKELY KEEP HIGH TEMPS EVEN COOLER SO LOWERED A FEW DEGREES MOST AREAS OUTSIDE OF THE FAR WESTERN SLOPES WITH MOST AGAIN STUCK IN THE 50S THIS AFTERNOON. PREVIOUS DISCUSSION AS OF 445 AM EDT FRIDAY... INCREASINGLY COMPLICATED FORECAST THROUGH THE NEAR TERM THANKS TO DEEPENING LOW PRESSURE AREA ALOFT ACROSS THE SOUTHEAST STATES. MODELS IN GENERAL AGREEMENT ON SYNOPTIC PATTERN...BUT QPF AND NORTHWARD EXTENT OF PCPN PROBLEMATIC. GFS BRINGS OVER AN INCH OR RAIN AS FAR NORTH AS SOUTHERN VA OVERNIGHT...WHILE NAM/ECMWF/CANADIAN KEEP PCPN AMOUNTS TO AROUND 1/4 INCH IN SOUTHERN VA AND PERHAPS UP TO 1/2 INCH IN NC COUNTIES. GFS HAS BEEN CONSISTENT LAST SEVERAL RUNS IN DEVELOPING A BAND OF HEAVIER RAIN ACROSS SW/SC VA...BUT THIS HAS NEVER BEEN INDICATED BY THE OTHER MODELS. WPC INDICATES GFS IS ODD SOLUTION AND AS A RESULT HAVE CHOSEN TO DISCARD HEAVIER RAINFALL AND FURTHER NORTHWARD EXTENT...EVEN INTO WV...INDICATED BY GFS. NONETHELESS...ALL MODELS HAVE TRENDED WETTER...FURTHER NORTH...WITH -RA POSSIBLY BEGINNING IN WESTERN NC EVEN LATE THIS AFTERNOON. EXTENSIVE HIGH CLOUD COVER HAS ALREADY OVERSPREAD THE REGION...AND SOME LOW CLOUDS CREEPING INTO EASTERN PIEDMONT COUNTIES. TEMPERATURES WILL RISE VERY LITTLE TODAY AND BE QUITE UNIFORM ACROSS THE REGION THROUGH THE NEAR TERM...MAINLY 50S FOR HIGHS TODAY AND 40S FOR LOW TONIGHT...WITH A FEW LOW 60S POSSIBLE IN FAR SW VA. E-NE FLOW WILL TEND TO KEEP AREAS EAST OF THE ALLEGHANY FRONT COOLER THAN NORMALLY COLDER WESTERN AREAS. MODEL GUIDANCE SIMILAR AND INTERESTING TO NOTE THAT ECMWF GRIDDED OVERNIGHT TEMPS NEAR 45 ACROSS ENTIRE CWA. WITH RESPECT TO FROST ADVISORY...HAVE CANCELLED ALL EXCEPT FOR A FEW OF THE ORIGINAL INCLUDED COUNTIES AS CLOUDS AND EAST FLOW HAVE PREVENTED DECOUPLING. IT NEVER EVEN GOT BELOW 40 AT DAN/LYH AS A RESULT. OPTED TO KEEP THE SOUTHERN SHENANDOAH VALLEY COUNTIES IN THROUGH 8 AM AS MESO OBS SHOW READINGS IN THE LOW 30S THERE YET WITH CALM WINDS...SO FROST QUITE LIKELY THERE. && .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... AS OF 230 AM EDT FRIDAY... SATURDAY MORNING...ONSHORE FLOW IN ASSOCIATION WITH A SLOW MOVING AREA OF LOW PRESSURE OVER GEORGIA IS STILL EXPECTED TO BE BRINGING PATCHY LIGHT RAIN TO THE SOUTHERN THIRD OF THE FORECAST AREA. AS THE DAY PROGRESSES...THE LOW WILL SHIFT SLOWLY EASTWARD...AND LIKEWISE WILL THE PRECIPITATION. CLOUD COVER ALSO WILL DECREASE IN COVERAGE FROM NORTHWEST TO SOUTHEAST. BY EARLY SATURDAY EVENING...THE PRECIPITATION IS EXPECTED TO OUT OF THE AREA...WITH THE CLOUD COVER CONTINUING TO EXIT. FOR HIGHS ON SATURDAY...HAVE FAVORED NUMBERS AROUND OR SLIGHTLY COOLER THAN THAT OF THE MAV MOS GIVEN THE NAM HAS SOLUTION WITH LESS CLOUD COVER AND PRECIPITATION. LIKEWISE FOR SATURDAY NIGHT...HAVE LEANED MORE TOWARD THE MAV MOS GUIDANCE. HEADING INTO SUNDAY...THE CLOSED LOW OVER THE SOUTHEAST U.S. CONTINUES ITS PROGRESSION EASTWARD INTO THE ATLANTIC. OVER OUR REGION...HIGH PRESSURE WILL BUILD OVERHEAD CONCURRENT TO AN UPPER RIDGE DEVELOPING OVER THE EASTERN U.S. THE RESULT WILL BE A PRECIPITATION-FREE FORECAST ON SUNDAY AND MONDAY WITH A TREND TOWARD MODERATING TEMPERATURES. && .LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 330 PM EDT WEDNESDAY... MONDAY LOOKS TO BE DRY WITH THE ATLANTIC SYSTEM WELL OUT TO SEA AND A WEAK RIDGE OF HIGH PRESSURE ALONG THE EASTERN SEABOARD AND SEASONAL TEMPERATURES. MODELS BRING A FAIRLY STRONG FRONT THROUGH THE CWA ON TUESDAY WITH GOOD CHANCES FOR SHOWERS AND POSSIBLE THUNDERSTORMS DEPENDING ON MESOSCALE FORCING IN PLACE AT THAT TIME. SKIES SHOULD CLEAR TUESDAY NIGHT INTO WEDNESDAY WITH NORTHWEST FLOW AND COOLER TEMPS BEHIND THE FRONT. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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AS OF 1240 PM EDT FRIDAY... HAVE BROKEN INTO OVERALL VFR EARLY THIS AFTERNOON AND SHOULD MAINTAIN INTO EARLY THIS EVENING WITH EXTENSIVE HIGH CLOUDS ON TOP OF SCTD LOW CLOUDS. STILL EXPECT CIGS TO LOWER OVERNIGHT BUT DEPTH OF MOISTURE REMAINS IN QUESTION UNDER DRY MID LEVELS AND DEVELOPING NE FLOW LATER ON. MODELS REMAIN VARIED ON HOW FAR NORTH TO TAKE LOWER CIGS AND RAINFALL AFTER MIDNIGHT WITH AN ENSEMBLE BLEND PROVIDING A RANGE FROM MOSTLY VFR OVERNIGHT AT LWB TO DEVELOPING IFR ALONG AND EAST OF THE BLUE RIDGE BY DAYBREAK SATURDAY. APPEARS MVFR TO OCNL IFR MOST LIKELY FROM ROA-LYH SOUTH TO DAN WHILE A PERIOD OF MVFR LIKELY AT BCB AND POSSIBLE AT BLF ALTHOUGH LOW CONFIDENCE AT THIS POINT. RAINFALL INDUCED VSBY REDUCTIONS ALSO IFFY WITH MVFR LIKELY AT DAN AND PERHAPS ROA/LYH IF THINGS SATURATE ENOUGH BY EARLY SATURDAY WHICH APPEARS POSSIBLE. ELSW INCLUDING SOME -RA/DZ MENTION AT BCB AND BLF LATE BASED ON LATEST NON NAM GUIDANCE TRENDS. LIGHT/VRBL WINDS TO PERSIST THIS AFTERNOON...THEN BECOMING NORTH/NE TONIGHT WITH SPEEDS INCREASING...PUSHING GUSTS TO 20 KTS OUT EAST BY MORNING. POOR FLYING CONDITIONS COULD PERSIST OVER THE SOUTH AND EAST INTO SATURDAY AFTERNOON WITH THE BELT OF DEEPER MOISTURE UNDER THE UPPER LOW SLOW TO EXIT. PERIODS OF -RA/DZ MAY ALSO LINGER EAST OF THE BLUE RIDGE WHERE ROA/LYH/DAN COULD GET STUCK IN MVFR TO IFR CIGS AND SOME LIMITED VSBY REDUCTION PENDING NORTHWARD EXTENT OF THE RAINFALL ESPCLY THROUGH MIDDAY. EXTENDED AVIATION DISCUSSION... THE UPPER LOW SLOWLY EXITS TO THE EAST SUNDAY AND HIGH PRESSURE RETURNS BRINGING A RETURN TO VFR CONDITIONS INTO EARLY NEXT WEEK. THE NEXT COLD FRONT APPROACHES MONDAY NIGHT WITH MORE SHOWERS AND POSSIBLE THUNDERSTORMS INCLUDING PERIODS OF MVFR. FRONT EXITS TUESDAY NIGHT RESULTING IN A RETURN TO VFR WEDNESDAY EXCEPT FOR MVFR CIGS OVER THE FAR WESTERN SITES IN SE WEST VA.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...RAB NEAR TERM...JH/KK/KM/RAB SHORT TERM...DS LONG TERM...PC AVIATION...JH/RAB

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