Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 131718 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 118 PM EDT SAT SEP 13 2014 .SYNOPSIS... A COLD FRONT THIS MORNING WILL BRING CANADIAN HIGH PRESSURE ACROSS OUR AREA TODAY. THIS HIGH PRESSURE WILL PASS FROM THE GREAT LAKES TO NEW ENGLAND TONIGHT...AND THEN BUILD SOUTHWARD ACROSS THE MID ATLANTIC FOR SUNDAY...PROVIDING COOLER THAN NORMAL TEMPERATURES. WARMER WEATHER RETURNS FOR MONDAY AS HIGH PRESSURE MOVES OFFSHORE...ALLOWING WINDS TO SHIFT SOUTHWESTERLY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 955 AM EDT SATURDAY... TNB...LWB...BLF AND PSK HAVE SHIFTED TO A NORTHWEST WIND AS A WEAK BOUNDARY CROSSES THROUGH THE AREA. THIS ROUGHLY LINES UP WITH THE BACK EDGE OF THE BETTER COVERAGE OF PRECIPITATION. RADAR TRENDS SINCE 8AM SHOWED THE WESTERN EDGE OF THE PRECIPITATION MOVING NORTHEAST AROUND 30 MPH. AS LONG AS THE BAND OF SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE MOVING AT THIS SPEED AND DIRECTION...THE BULK OF THE PRECIPITATION WILL BE EXITING THE EASTERN COUNTY WARNING AREA AROUND 18Z/2PM. HAVE ADJUSTED PROBABILITY OF PRECIPITATION FOR THESE TRENDS. ONLY MINOR ADJUSTMENTS MADE TO MAXIMUM TEMPERATURES FOR TODAY. NORTHWEST WINDS WILL AIDE IN EXPANDING BREAKS IN THE CLOUD COVER JUST EAST OF THE BLUE RIDGE THIS AFTERNOON. CANADIAN HIGH PRESSURE BUILDING IN BEHIND THE COLD FRONT WILL PUSH ACROSS THE LOWER GREAT LAKES THIS EVENING AND TONIGHT... GRADUALLY SHIFTING WINDS ACROSS OUR AREA FROM NORTHWESTERLY BY SUNSET TO NORTHEASTERLY BY SUNRISE SUNDAY. WHILE MUCH OF OUR AREA WILL BE DRY SATURDAY NIGHT...LOOKS LIKE THERE WILL BE ENOUGH RESIDUAL MOISTURE BEING FORCED UP THE BLUE RIDGE BY SUNDAY MORNING TO SUPPORT LIGHT RAIN ACROSS THE NORTH CAROLINA MOUNTAINS. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... AS OF 345 AM EDT SATURDAY... ON SUNDAY MORNING...HIGH PRESSURE WILL BE IN THE PROCESS OF SHIFTING FROM THE GREAT LAKES INTO NEW ENGLAND...AND WILL THEN BEGIN TO BUILD SOUTHWARD ACROSS THE MID ATLANTIC TO BUTT UP AGAINST THE EASTERN FACE OF THE APPALACHIANS. FORECAST MODELS HAVE BECOME MORE AGGRESSIVE IN PUSHING THE COLD FRONT FURTHER SOUTH OF OUR AREA COMPARED TO MODEL RUNS FROM 24 HOURS AGO...INDICATING THAT DRIER AIR WILL BE IN PLACE FOR SUNDAY WITH LOWER RAIN CHANCES OUR FORECAST REGION. THE CAVEAT TO THAT STATEMENT LIES IN THE NORTH CAROLINA MOUNTAINS...WHERE NORTHEASTERLY WINDS WRAPPING AROUND THE HIGH WILL CARRY MARINE AIR UP THE BLUE RIDGE...SUPPORTING MORNING DRIZZLE AND AFTERNOON SPOTTY SHOWER ACTIVITY THAT MAY BECOME MODERATE IN INTENSITY FOR BRIEF PERIODS OF TIME. WITH HIGH PRESSURE IN PLACE... ALSO CONTINUING THE TREND OF UNDERCUTTING MODEL GUIDANCE FOR AFTERNOON TEMPERATURES...HOLDING HIGHS TO THE MID/UPPER 60S MOST LOCATIONS. THE EXCEPTION MAY BE ACROSS PORTIONS OF THE MOUNTAIN EMPIRE WHICH ARE BUFFERED FROM THE COOL HIGH PRESSURE BY THE HIGHER RIDGELINES. TEMPERATURES WEST OF THESE RIDGES MAY WARM INTO THE MID 70S IF THE SUN BREAKS OUT OF THE CLOUDS. ON MONDAY...HIGH PRESSURE WILL MOVE OFFSHORE...ALLOWING WINDS TO SHIFT SOUTHWESTERLY AS ANOTHER UPPER LEVEL DISTURBANCE AND ASSOCIATED COLD FRONT APPROACH FROM THE MIDWEST. SOUTHWESTERLY FLOW WILL RETURN GULF MOISTURE NORTHWARD ALONG THE APPALACHIAN CHAIN...WHICH WILL PUSH DEWPOINT TEMPERATURES BACK INTO THE 60S ACROSS MUCH OF THE AREA AND PRECIPITABLE WATER VALUES INTO THE 1.1 TO 1.5 INCH RANGE. AND WITH MONDAY AFTERNOON TEMPERATURES WARMING INTO THE MID TO UPPER 70S...BELIEVE WE WILL HAVE ENOUGH INSTABILITY TO SUPPORT SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO MONDAY EVENING AS THE FRONT NEARS OUR AREA. THE COLD FRONT WILL PASS ACROSS OUR AREA MONDAY NIGHT...ALLOWING DRIER AIR TO WORK IN FROM THE GREAT LAKES REGION. INCREASED SUNSHINE ON TUESDAY WILL ALLOW AFTERNOON TEMPERATURES TO REACH THE UPPER 60S/LOW 70S ACROSS THE MOUNTAINS...AND RISE INTO THE MID/UPPER 70S ACROSS THE PIEDMONT. TUESDAY NIGHT LOWS WILL BE GENERALLY IN THE 50S. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 130 PM EDT FRIDAY... A BROAD UPPER TROUGH WILL GRADUALLY DEEPEN ACROSS THE EASTERN STATES NEXT WEEK...ALLOWING A LARGE AREA OF HIGH PRESSURE PASSING ACROSS THE GREAT LAKES TO EVENTUALLY WEDGE SOUTH ALONG THE MOUNTAINS BY NEXT WEEKEND. THIS SHOULD PROMOTE MAINLY DRY WEATHER...ALTHOUGH CANNOT TOTALLY RULE OUT ISOLATED SHOWERS DURING THE SECOND HALF OF THE WEEK OVER THE SOUTH PER ANOTHER PASSING SHORTWAVE...BUT THIS APPEARS REMOTE GIVEN DRY AIR AND LATEST MODEL TRENDS. THUS PLANNING TO KEEP THE END OF THE WEEK MOSTLY DRY OUTSIDE OF AN ISOLATED SHOWER MENTION FAR SOUTH-EAST WEDNESDAY-EARLY THURSDAY. HIGHS MAINLY MID 60S TO AROUND 70 WEST AND 70-75 EAST WITH LOWS MOSTLY 50S...EXCEPT FOR A FEW COOLISH 40S IN THE VALLEYS GIVEN THE SURFACE RIDGE AXIS ABOUT OVERHEAD. && .AVIATION /17Z SATURDAY THROUGH WEDNESDAY/... AS OF 100 PM EDT SATURDAY... WEAK SFC FRONT CONTINUES TO PUSH THROUGH THE AREA AS HIGH PRESSURE BUILDING INTO THE OHIO VALLEY FLOPS OVER THE TOP OF US THROUGH TOMORROW. THIS WILL GIVE US A BIT OF NW FLOW WEATHER EARLY...WITH WINDS ONCE AGAIN BECOMING E/NELY AND SOME MOISTURE RETURN ALONG THE BLUE RIDGE. EAST OF THE BLUE RIDGE FOR KLYH AND KDAN...EXPECT CIGS TO RISE AOA VFR LEVELS DURING THE FIRST PART OF THE TAF PERIOD WITH KDAN TAKING THE LONGEST. OVERNIGHT NELY FLOW RETURNS BUT INDICATIONS ARE THAT LOWER CIGS WILL SKIRT THE AREA. WILL GO OPTIMISTIC AND INDICATE ONLY VFR BUT KDAN STANDS THE BETTER CHANCE OF SEEING SOME MVFR CIGS OVERNIGHT. ALONG THE BLUE RIDGE FOR KBCB AND KROA...EXPECTING SOME IMPROVEMENT TO VFR THIS AFTERNOON. BUT AS LIGHT WIND BECOMES E/NELY MOISTURE RUNNING UP THE SLOPES WILL LIKELY GENERATE A RETURN TO LOWER CIGS. KBCB MAY ALSO SEE SOME DRIZZLE AND -SHRA AS THE MOISTURE LOOKS TO BE GREATER HERE AND WILL COMBINE WITH SOME WAA ALOFT TO SQUEEZE OUT SOME PCPN. WEST OF THE BLUE RIDGE...EXPECT KBLF TO STAY LOCKED INTO LOW CIGS WITH A SLIGHT LIFT FROM IFR TO MVFR THIS EVENING BEFORE GOING BACK TO IFR AS DEEPER MOISTURE AND PREVIOUSLY MENTIONED WAA ARRIVE. KLWB MAY SCATTER OUT THIS EVENING...LEADING TO THE QUESTION OF HOW MUCH RADIATION CAN TAKE PLACE TO GENERATE FOG/STRATUS. IT SEEMS LIGHT NE FLOW WILL ENTER KLWB DURING PRIME FOG TIME SO THIS MAY KEEP THINGS FROM BOTTOMING OUT. WILL INDICATE THIS BUT THE SITUATION COULD GO EITHER WAY. EXTENDED AVIATION DISCUSSION... BUT OVERALL CONDITIONS SHOULD BE MOSTLY MVFR...WITH LESS IFR OR WORSE CIGS/VSBYS. BEYOND SUNDAY...BROAD UPPER TROUGH DEVELOPING ACROSS THE NORTHERN STATES...WITH THE RNK CWA ON THE SOUTHERN EDGE OF THIS BROAD UPPER TROUGH...LEADING TO PRIMARILY CONTINUED ZONAL FLOW. LATEST MODEL TRENDS BEGINNING TO FAVOR POTENTIAL CHANGE TO A MORE NW FLOW ALOFT AS THE WEEK PROGRESSES...WHICH SHOULD ATTEMPT TO PUSH THE PESKY DEEP MOISTURE FURTHER SOUTH AWAY FROM THE REGION. OVERALL...EXPECT MVFR CONDITIONS TO PERSIST INTO MONDAY AS AFOREMENTIONED UPPER TROUGH BRINGS MORE CLOUDS AND SHOWERS TO THE REGION. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...AMS/NF SHORT TERM...NF LONG TERM...JH AVIATION...MBS/NF

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