Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230528 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 128 AM EDT TUE SEP 23 2014 .SYNOPSIS... HIGH PRESSURE SYSTEM WILL MOVE EAST TONIGHT COVERING MUCH OF THE EASTERN UNITED STATES THROUGH WEDNESDAY. LOW PRESSURE WILL DEVELOP ALONG THE SOUTHEAST COAST THURSDAY AND FRIDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 830 PM EDT MONDAY... NOT A LOT OF CHANGE OVERNIGHT WITH LOW CLOUDS ACROSS THE FAR WEST SLOWLY FADING WHILE PERSISTENT AXIS OF HIGH LEVEL MOISTURE CONTINUES TO SHEAR NORTH ACROSS THE REMAINDER OF THE REGION ATTM. MOST GUIDANCE HUMIDITY FIELDS KEEP THIS CANOPY OF HIGH CLOUDS AT LEAST OVER THE EAST THROUGH MORNING WITH THE GFS EVEN BENDING BACK WESTWARD IN RESPONSE TO THE DEVELOPING CUTOFF 5H SYSTEM TO THE SOUTH. HOWEVER APPEARS GIVEN VERY DRY AIR OFF EVENING SOUNDINGS THAT MOST CIRRUS OUTSIDE OF THE PIEDMONT SHOULD STAY THIN ENOUGH TO ALLOW GOOD RADIATIONAL COOLING AS THE SURFACE HIGH SINKS IN FROM THE NORTH OVERNIGHT. LATEST LAV MOS SIMILAR TO EARLIER FORECAST LOWS SO ONLY MAKING SMALL ADJUSTS...MAINLY TO LOWER A BIT IN A FEW MORE OF THE WESTERN VALLEYS WHERE EARLIER COOP MOS WAS THE COLDEST. ALSO ADDED A BIT MORE DEEP VALLEY FROST BUT GIVEN WARM GROUND TEMPS/VEGETATION AND FOG POTENTIAL APPEARS ANY FROST VERY BRIEF AND NOT ENOUGH FOR ANY HEADLINES AT THIS POINT. ALSO GIVEN CURRENT WIDE TEMP/DEWPT SPREAD IN SPOTS...SLOWING DOWN FOG FORMATION A WHILE LONGER TO MOSTLY THE EARLY MORNING HOURS FOR NOW. OTRW CALLING IT CLEAR TO PC THROUGH HIGH CLOUDS WITH LOWS 37-44 FAR WEST...LOW/MID 40S BLUE RIDGE...AND LOW 50S SE WHERE MORE CLOUDS AND HIGHER DEWPOINTS SHOULD NEGATE COOLING TO SOME DEGREE. PREVIOUS VALID DISCUSSION AS OF 230 PM EDT MONDAY... HIGH PRESSURE TO MOVE OVER THE MID ATLANTIC LATE TONIGHT. CLOUDS THIS AFTERNOON WILL ERODE IN THE MOUNTAINS TONIGHT BUT AT THE SAME TIME AS UPPER LEVEL SYSTEM MOVES ACROSS THE WESTERN CAROLINAS AND CLOSES OFF...EXPECT THE UPPER LEVELS TO MOISTEN UP AND SEND SOME CIRRUS NORTH ACROSS THE EASTERN HALF OF THE FORECAST AREA...THOUGH NOT TOO CONFIDENT ON DENSITY OF THE CIRRUS...BUT THINK THE SKY WILL BE PARTLY CLOUDY. BIG ISSUE TONIGHT WILL BE TEMPS...AS WINDS DECOUPLE...AND SKY IN THE WEST TO BE CLEAR. THINK TEMPS WILL BE DROPPING INTO THE MID TO UPPER 30S ACROSS THE VALLEYS OF BATH AND GREENBRIER WITH MOST STAYING ABOVE 37F. PATCHY FROST IN THE VALLEYS APPEARS POSSIBLE SO HIGHLIGHT BATH AND GREENBRIER IN THE HWO FOR PATCHY FROST. NOT ENOUGH COVERAGE TO WARRANT A FROST ADVISORY BUT EVENING SHIFT CAN TAKE ANOTHER LOOK AT TRENDS IN TEMP/DEWPOINT/WIND/SKY IN CASE THREAT OF MORE FROST INCREASES. NONETHELESS THE COOLEST NIGHT WE HAVE HAD SINCE LATE MAY...WITH UPPER 30S/LOWER 40S MOUNTAINS...TO MID 40S-50 EAST. DURING THE DAY TUESDAY...UPPER LOW/TROUGH STAYS OVER THE CENTRAL PORTIONS OF THE CAROLINAS...AND MAINLY KEEPING A STREAM OF HIGH CLOUDS SITUATED OVER THE PIEDMONT. HIGH WILL BE MILD WITH UPPER 60S TO LOWER 70S ACROSS MUCH OF THE CWA. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... AS OF 240 PM EDT MONDAY... STILL LOOKING DRY TUESDAY NIGHT BUT MODEL DIFFERENCES SHOW UP IN TERMS OF THIS UPPER TROUGH INTO WEDNESDAY...AND HOW MUCH MOISTURE SPREADS WEST FROM THE EAST FLOW AROUND THE WEDGE. THE ECMWF HAS BEEN PERSISTENT IN SHOWING THIS AND THE 12Z NAM IS COMING INTO THIS TREND AS WELL...WITH THE GFS STILL DRIER. THINK THE DRY LOW LVLS WILL TAKE A WHILE TO MOISTEN UP BUT LATE WED NIGHT-THU SHOULD SEE ENOUGH BETWEEN THE HIGH OVER THE NE/MID ATLANTIC AND A COASTAL TROUGH/FRONT/LOW TO BRING A SLIGHT CHANCE TO LOW CHANCE OF RAIN TO THE EASTERN HALF OF THE CWA...WITH CLOUDS INCREASING. THE WEDGE IN PLACE WILL MAKE FOR A COOLER DAY THURSDAY...THAN WEDNESDAY. HIGHS WEDNESDAY WITH MORE SUN WILL WARM INTO THE UPPER 60S TO MID 70S...THEN WITH CLOUDS AND LIGHT RAIN THURSDAY EXPECT MID TO UPPER 60S WHERE ITS CLOUDY WITH RAIN CHANCES...WITH LOWER TO MID 70S ACROSS THE FAR SW VA CORRIDOR HEADING WEST OF MARION AND TAZEWELL. LOWS WILL ALSO MODIFY DURING THIS PERIOD...BUT STILL COOL WED MORNING WITH LOWER 40S MOUNTAIN VALLEYS...TO MID TO UPPER 40S MOST LOCATIONS...EXCEPT LOWER 50S SOUTHEAST. LOWS THURSDAY MORNING WILL BE IN THE 50 TO 55 DEGREE RANGE. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
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AS OF 300 PM EDT MONDAY... CONSIDERABLE UNCERTAINTY EXISTS IN THE EXTENDED PERIOD AS A FAIRLY COMPLEX UPPER LEVEL PATTERN DEVELOPS BY THE WEEKEND WITH HIGHLY AMPLIFIED UPPER RIDGE OVER THE NORTH CENTRAL U.S. EXTENDING INTO CANADA WITH TROUGHING OVER THE WESTERN ATLANTIC AND ACROSS THE WESTERN STATES. THE 12Z EURO IS MUCH FURTHER WEST WITH ATLANTIC TROUGH WITH RESULTANT SURFACE LOW MEANDERING ALONG THE MID- ATLANTIC COAST FRI-SAT BUT NOT FAR ENOUGH WEST FOR PRECIP THIS FAR INLAND. BUT WOULD LIKELY SEE SUBSTANTIAL CLOUDINESS FROM THIS ALONG WITH THE CAD-LIKE EFFECTS FROM A VERY SLOW-MOVING SURFACE HIGH OVER THE NORTHEAST. IN FACT THE UPPER RIDGE TO THE NORTH RETARDS THE NORTHWARD MOVEMENT OF THIS COASTAL SYSTEM WELL INTO SUNDAY. GFS IS MUCH LESS DEVELOPED WITH ANY COASTAL SYSTEM WITH DRY HIGH PRESSURE IN CONTROL THROUGH WEEKEND. ELECTED TO REFLECT MORE OPTIMISTIC GFS SOLUTION AT THIS POINT WITH MORE SUN. TEMPS NEAR TO ABOVE NORMAL WITH MAINLY 70S AND 50S FOR HIGHS/LOWS. BOTH GFS/EURO SHOW SURFACE LOW OR INVERTED TROUGH DEVELOPING OVER THE LOWER MISSISSIPPI VALLEY BY EARLY NEXT WEEK WITH GRIDS SHOWING CLOUDS SPREADING IN FROM SW TO NE AS EARLY AS SUNDAY NIGHT.
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&& .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 125 AM EDT TUESDAY... EXPECTING VFR CONDITIONS TO PREVAIL OVERNIGHT AT KROA/KLYH/KBLF AND KDAN. SCATTERED TO BROKEN HIGH CLOUDS WILL MUCH OF CENTRAL AND EASTERN VIRGINIA AND NORTH CAROLINA TODAY AND TONIGHT. GOOD RADIATIONAL COOLING WILL LEAD TO PATCHY RIVER BOTTOM FOG. THIS WILL RESULT IN A FEW HOURS OF LIFR CONDITIONS AT KLWB. MVFR/IFR CONDITIONS POSSIBLE AT KBCB FOR AN HOUR OR TWO RIGHT AROUND DAWN. BY 14Z/10AM TUESDAY ALL TAF LOCATIONS WILL BE VFR AND HIGH CONFIDENCE THAT CONDITIONS WILL STAY VFR THROUGH THE REMAINDER OF THE TAF PERIOD. EXTENDED AVIATION DISCUSSION... HIGH PRESSURE AND DRIER AIR IN THE REGION THROUGH WEDNESDAY WILL RESULT IN MAINLY VFR CONDITIONS. RIVER VALLEY FOG WILL STILL BE POSSIBLE AT NIGHT AS WINDS DIMINISH AND COOL AIR MASS DECOUPLES. THERE IS STILL SOME MODEL DIFFERENCES REGARDING A LOW PRESSURE SYSTEM FORMING FROM THE GULF COAST LATER THIS WEEK. SEVERAL MODELS SHOW MOISTURE INCREASING OVERNIGHT WEDNESDAY THROUGH THURSDAY EVENING WHICH MAY RESULT IN PERIODS OF IFR/MVFR CEILINGS AND VSBYS. APPEARS HIGH PRESSURE WILL AGAIN RE-ESTABLISH OVER THE REGION LATE IN THE WEEK RESULTING IN RETURN TO WIDESPREAD VFR BY THE WEEKEND.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...JH/WP SHORT TERM...WP LONG TERM...PC AVIATION...AMS/JH

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