Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 181145 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 745 AM 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 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 /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 745 AM EDT FRIDAY... MODELS CONTINUE TO PRESENT CHALLENGES IN THE FORECAST...WHICH HAS NOW TRANSLATED EVEN INTO THE NEAR TERM PORTION OF THE TAF. EARLIER GFS INDICATED THAT LOW CLOUDS ON ESE MARITIME FLOW WOULD WORK THEIR WAY INTO LYH/ROA/DAN THIS MORNING...WHILE NAM/ECMWF GENERALLY DISCOUNTED THIS. IT APPEARS THE GFS WAS RIGHT...AS 09Z-10Z...LOW END MVFR CIGS WORKED THEIR WAY INTO ROA/LYH/DAN. GFS GRIDDED DATA STILL SEEMS TO HAVE A GOOD HANDLE ON THIS...WHILE LATEST GFS MOS DATA DOES NOT. THE AREA OF LOW CLOUDS APPEARS TO BE CONFINED TO A SMALL AREA WITHIN ABOUT 100 MILES E-SE OF THE BLUE RIDGE. MODELS SHOW THIS SHOULD BEGIN TO BREAK UP MID TO LATE MORNING...SO HAVE PLANNED ACCORDINGLY WITH VFR CIGS ALL SITES BY 16Z. LOW CLOUDS SHOULD NOT WORK THEIR WAY INTO LWB/BLF...BUT WILL NEED TO WATCH BLF WITH SE WINDS AND BCB NOW OVC013. AT ANY RATE...EXTENSIVE HIGH CLOUDS WILL CONTINUE ON TOP OF ANY LOW CLOUDS WITH HIGH CLOUD CIGS LOWERING INTO THE 100 RANGE BY 00Z. LOW CLOUDS WILL REDEVELOP...ESPECIALLY EAST OF THE BLUE RIDGE...WITH MVFR CIGS ROA/LYH/DAN/BCB AFT 06Z...POTENTIALLY IFR DAN. HAVE INTRODUCED -RA ROA/DAN/LYH 08Z AND BEYOND WITH -DZ BCB. MOST MEASURABLE RAIN WILL REMAIN EAST OF THE BLUE RIDGE. WINDS ESE 5-10KTS BACKING MORE TOWARD NE BY DAYS END...WITH LOW END GUSTS ALSO DEVELOPING EAST OF THE BLUE RIDGE AFT 06Z. MEDIUM CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... EVENTUALLY -RA AND MVFR TO POSSIBLY IFR CIGS WILL CREEP INTO THE SE PART OF THE CWA SATURDAY. LWB AND POSSIBLY EVEN BLF SHOULD REMAIN VFR MOST OF THIS TIME...BUT SOME MVFR POSSIBLE AT BLF. STILL MANY UNCERTAINTIES REGARDING SE U.S. UPPER LOW AND IMPACT ON AVIATION CONDITIONS ACROSS THE REGION...BUT MAIN IMPACT SHOULD CLEARLY BE FOR DAN/LYH/ROA AT THIS POINT. AS THAT SYSTEM EXITS TO THE EAST SUNDAY AND HIGH PRESSURE RETURNS FOR THE REMAINDER OF THE WEEKEND...EXPECT VFR CONDITIONS TO RETURN. THE NEXT SYSTEM TO BRING MVFR TO POTENTIALLY IFR CIGS AND -SHRA TO THE AREA DOES NOT ARRIVE UNTIL EARLY TO MID PART OF NEXT WEEK.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR VAZ023-024-035- 047. NC...NONE. WV...NONE. && $$ SYNOPSIS...RAB NEAR TERM...KK/KM/RAB SHORT TERM...DS LONG TERM...PC AVIATION...KK/RAB

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