Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 202347 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 747 PM EDT SUN APR 20 2014 .SYNOPSIS... SLOW MOVING LOW PRESSURE OFF THE CAROLINAS WILL DRIFT EAST AND OFFSHORE TONIGHT. STRONG HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA FROM OFF THE MID ATLANTIC COAST OVERNIGHT AND REMAIN IN PLACE INTO MONDAY. A COLD FRONT ARRIVES LATER TUESDAY WITH THE NEXT CHANCE OF SHOWERS AND STORMS. && .NEAR TERM /THROUGH MONDAY/... AS OF 711 PM EDT SUNDAY... SMALL ADJUSTMENTS WERE MADE IN TEMPS IN THE NEW RIVER AND ROANOKE VALLEYS... DROPPING THEM A COUPLE DEGREES. CLOUD COVER WAS REDUCED FROM 22Z TO 06Z MONDAY TO FIT THE TRANSITION AS THE LOW MOVES OUT TO SEA. DEWPOINT TEMPERATURES WERE MODIFIED ACCORDING TO SURFACE OBSERVATION TREND. AS OF 215 PM EDT SUNDAY... LOW PRESSURE OFFSHORE THE CAROLINAS WILL FINALLY GET BUMPED EAST OVERNIGHT ALLOWING STRONG SURFACE HIGH PRESSURE OFF NEW ENGLAND TO BUILD SW AND BE PARTIALLY OVERHEAD BY MORNING. THIS ALONG WITH ANOTHER FLUX OF DRY AIR UNDER INCREASING SHORTWAVE RIDGING SUPPORTS GOING CLEAR OVERNIGHT WITH JUST SOME HIGH CLOUDS AROUND MAINLY SE EARLY. GIVEN THE LOW DEWPOINT AIR IN PLACE AND POTENTIAL FOR ALL EXCEPT THE RIDGES AND PIEDMONT TO DECOUPLE UNDER CLEAR SKIES...SHOULD SEE QUITE A DIURNAL SWING WITH LOWS GOING DOWN CLOSE TO IF NOT BELOW THE COOLER MAV MOS IN SPOTS. LIKELY TO EVEN SEE A FEW 20S IN THE VALLEYS WHILE SOME CONCERN FOR AT LEAST SCTD/PATCHY FROST IN THE EAST WHERE THE GROWING SEASON HAS STARTED. HOWEVER APPEARS TEMPS THERE WONT FALL OFF TOO FAST UNTIL LATE WHEN WINDS FADE...WHILE DRYNESS PER DEWPOINT DEPRESSIONS...DOESNT SUPPORT MUCH FROST EVEN IF TEMPS DROP INTO THE LOWER 30S IN THE BOTTOMS. THUS ONLY ADDING IN SOME PATCHY FROST FOR AN HOUR OR TWO IN THE EAST LATE INCLUDING HWO MENTION FOR THE OUTLYING AREAS TOWARD DAWN. OTRW CHILLY OVERNIGHT WITH LOWS MOSTLY IN THE 30S EXCEPT 40S RIDGES SIMILAR TO THE PREVIOUS EC MOS. RIDGING BOTH SFC/ALOFT WILL GRADUALLY START TO WEAKEN MONDAY WITH THE APPROACH OF THE UPSTREAM 5H TROF/COLD FRONT. HOWEVER DRY AIR WILL STILL PREVAIL UNDER NORTH/NW TRAJECTORIES ALOFT AS THE FLOW REMAINS MUCH WEAKER DESPITE A QUICK SURGE IN 85H WARMING. COULD SEE SOME MID/HIGH CLOUDS INVADE THE WEST WELL AHEAD OF THE FRONT LATE BUT NOT ENOUGH TO DETER A MAINLY SUNNY DAY. TEMPS SHOULD GET ANOTHER BOOST WITH HEATING ALTHOUGH ONLY LIGHT MIXING MAY KEEP VALUES JUST BELOW THE VERY WARM MAV MOS FOR NOW WITH 70S MOST SPOTS. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 245 PM EDT SUNDAY... MONDAY NIGHT...MOISTURE WILL CONTINUE TO POOL INTO THE AREA IN ADVANCE OF AN APPROACHING COLD FRONT. ANTICIPATE MILDER LOW TEMPERATURES THAN THOSE OF SUNDAY NIGHT...WITH MID TO UPPER 40S COMMON ACROSS MOST OF THE AREA. ISOLATED TO SCATTERED SHOWERS IN ADVANCE OF THE FRONT ARE EXPECTED WEST OF THE BLUE RIDGE BY SUNRISE TUESDAY. THE FRONT WILL CROSS THE AREA DURING THE DAY ON TUESDAY WITH THE FOCUS FOR THE BEST COVERAGE BEING IN THE CENTRAL AND WESTERN PARTS OF THE AREA DURING THE MORNING. BY THE AFTERNOON... THE FOCUS JUMPS TO THE PIEDMONT. NORTHWEST WINDS BEHIND THE FRONT WILL YIELD A QUICK CLEAR OUT OF THE PRECIPITATION AND CLOUDS TUESDAY EVENING...WITH THE POTENTIAL FOR SOME ISOLATED SE WV UPSLOPE SHOWERS THROUGH MIDNIGHT. WHILE INSTABILITY FACTORS OFFER THE POTENTIAL FOR SOME ISOLATED THUNDERSTORMS ON TUESDAY...CONFIDENCE ON SEVERE STORMS IS LOW. WINDS WILL BE GUSTY IN THE WAKE OF THE DEPARTING COLD FRONT AND THE APPROACH OF HIGH PRESSURE. ACROSS THE HIGHER TERRAIN...GUSTS OF 20 TO 30 MPH WILL BE COMMON TUESDAY AFTERNOON AND NIGHT. ON WEDNESDAY...DRIER AND COOLER HIGH PRESSURE WILL STARTING BUILDING INTO THE AREA FROM THE NORTHWEST. WHILE NOT AS STRONG AS TUESDAY NIGHT...ENOUGH OF A PRESSURE GRADIENT WILL STILL BE IN PLACE TO WARRANT GUSTS IN THE MOUNTAINS APPROACHING 20 MPH. AREAS EAST OF THE BLUE RIDGE WILL BE NOTABLY WEAKER. WEDNESDAY NIGHT...THE CENTER OF THE SURFACE HIGHS MOVES OVER...AND THEN EAST OF THE REGION BY THURSDAY MORNING. EXPECT A RETURN OF LOW TO MID 30S FOR LOWS ACROSS THE MOUNTAINS WITH UPPER 30S TO LOWER 40S EAST OF THE BLUE RIDGE. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 1245 PM EDT SUNDAY... A RIDGE OF HIGH PRESSURE WILL BECOME CENTERED OVER THE REGION ON THURSDAY...AND START TO SHIFT TO THE COAST BY FRIDAY MORNING. THE RESULT WILL BE PROGRESSIVE MODERATING TEMPERATURES AS LOW LEVEL WINDS STRENGTHEN FROM THE SOUTHWEST AND WARM AIR ADVECTION PREDOMINATES. AS THE RIDGE MOVES EAST...A COLD FRONT WILL APPROACH THE AREA FRIDAY MORNING AND BE EAST OF THE AREA BY FRIDAY EVENING. SCATTERED SHOWERS AND SOME ISOLATED THUNDERSTORMS WILL ACCOMPANY THE FRONT. BEHIND THE FRONT...MODEL GUIDANCE DEVIATES ENOUGH TO PROVIDE UNIQUELY DIFFERENT WEATHER PATTERN SOLUTIONS FOR OUR REGION OF THE COUNTRY. THE GFS SOLUTION DEEPENS THE PARENT LOW OF THE COLD FRONT AND BRINGS IT SOUTH TO CAPE COD BY SUNDAY MORNING. THIS KEEPS A PREVAILING NORTHWEST FLOW WHICH IS DRY AND PROGRESSIVELY COOLER ACROSS THE AREA. THE ECMWF DOES NOT DEEPEN THE COLD FRONT/S PARENT LOW...AND EJECTS ITS QUICKLY EASTWARD MORE AS AN OPEN WAVE. THIS ALLOWS FOR A QUICKER RETURN OF ZONAL FLOW TO THE AREA THAT HAVE THE POTENTIAL TO BRING CENTRAL U.S. SYSTEMS INTO OR TOWARD THE AREA BY THE END OF THE WEEKEND...ALONG WITH HAVING A MILDER PATTERN. OUR FORECAST WILL REFLECT THE GUIDANCE PROVIDED BY WPC WHICH LEANS MORE CLOSELY TO THE ECWMF SOLUTION. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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AS OF 745 PM EDT SUNDAY... VFR CONDITIONS EXPECTED TO CONTINUE THROUGH THE TAF VALID PERIOD. SLOW MOVING CLOSED UPPER LOW OFF THE SC/NC COAST WILL CONTINUE TO DRIFT SLOWLY EAST THROUGH THE PERIOD. NEXT UPSTREAM SYSTEM DEVELOPING THROUGH THE MID-SECTION OF THE U.S. IN BETWEEN...RIDGE OF HIGH PRESSURE FROM THE MID-SOUTH INTO THE MID-ATLANTIC REGION WILL DOMINATE THE WEATHER THROUGH THE TAF VALID PERIOD. HIGH CLOUDS WILL BE ON THE INCREASE AFTER DAYBREAK MON AS MID-U.S. SYSTEM MOVES TOWARD THE REGION...BUT CIGS WILL REMAIN VFR THROUGH THE TAF VALID PERIOD. NO ISSUES WITH VSBYS THROUGH THE TAF VALID PERIOD EITHER. WINDS...TO START...NE ACROSS THE PIEDMONT...E-SE WEST OF THE BLUE RIDGE. AS LOW PRESSURE MOVES AWAY TO THE EAST AND HIGH PRESSURE DRIFTS OVER THE REGION...EXPECT WINDS TO BECOME VARIABLE OVERNIGHT/EARLY MON...THEN TRANSITION TO THE SW BY MON AFTERNOON. SPEEDS WILL REMAIN AOB 10KTS THROUGH THE TAF VALID PERIOD...BUT SOME LOW END GUSTS ARE POSSIBLE THROUGH THE EVENING ACROSS THE PIEDMONT. HIGH CONFIDENCE IN VFR CIGS/VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN WIND SPD/DIR THROUGH 12Z...THEN LOW CONFIDENCE IN WIND DIR...MEDIUM TO HIGH CONFIDENCE IN WIND SPD. EXTENDED AVIATION DISCUSSION... THE NEXT COLD FRONT APPROACHES MONDAY NIGHT WITH MORE SHOWERS AND POSSIBLE THUNDERSTORMS...WITH LOCALIZED MVFR FLIGHT RESTRICTIONS ON TUESDAY. THE FRONT EXITS TUESDAY NIGHT...RESULTING IN A RETURN TO VFR WEATHER AND GUSTY NW WINDS ON WEDNESDAY...EXCEPT FOR THE POTENTIAL OF SOME MVFR CIGS OVER THE FAR WESTERN UPSLOPE SITES IN SE WEST VA. HIGH PRESSURE BUILDS IN FOR THURSDAY...WITH WIDESPREAD VFR LIKELY. ANOTHER FAST MOVING COLD FRONT ARRIVES FOR FRIDAY WITH A PERIOD OF MVFR POSSIBLE IN SHOWERS/ISOLATED STORMS INTO FRIDAY EVENING.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/PH NEAR TERM...JH/KK SHORT TERM...DS LONG TERM...DS AVIATION...JH/RAB

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