Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 030136 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 936 PM EDT SUN AUG 2 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN ACROSS THE AREA TONIGHT INTO MONDAY KEEPING MAINLY DRY WEATHER IN PLACE. A COLD FRONT DROPS SOUTHEAST INTO THE REGION BY TUESDAY BEFORE STALLING OUT DURING MIDWEEK. LOW PRESSURE WILL RIDE ALONG THE FRONT BRINGING A BETTER CHANCE FOR MORE WIDESPREAD SHOWERS AND STORMS THURSDAY INTO FRIDAY. && .NEAR TERM /THROUGH MONDAY/... AS OF 930 PM EDT SUNDAY... NO MAJOR CHANGES ARE BEING MADE TO THE FORECAST FOR THE OVERNIGHT PERIOD. THE AREA STILL LOOKS TO HAVE A RELATIVELY COOL NIGHT WITH A MIX OF MID TO UPPER 50S ACROSS THE MOUNTAINS...AND AROUND 60 TO LOWER 60S ACROSS THE PIEDMONT. PATCHY FOG IS EXPECTED TO DEVELOP LATE TONIGHT INTO EARLY MONDAY MORNING. HAVE MADE SOME MINOR ADJUSTMENTS TO THE TEMPERATURE...DEW POINT AND SKY COVER THROUGH THE NEXT FEW HOURS BASED UPON THE LASTEST OBSERVATIONS AND EXPECTED TRENDS. AS OF 630 PM EDT SUNDAY... HEADING INTO THE EVENING HOURS...THE FORECAST IS ON TRACK FOR WINDS TO BECOME CALM WITH DECREASING CLOUD COVER. BY 1000 PM...TEMPERATURES WILL FALL INTO THE MID TO UPPER 60S ACROSS THE MOUNTAINS AND THE LOWER 70S ACROSS THE PIEDMONT. NO PRECIPITATION IS EXPECTED. AS OF 310 PM EDT SUNDAY... HIGH PRESSURE OVER THE REGION WILL BRING QUIET WEATHER TO THE REGION ONCE AGAIN TONIGHT. EXPECTED LIGHT WINDS...SCANT CLOUD COVER...AND LOW DEW POINTS WILL MAKE FOR GOOD RADIATIONAL COOLING AND A REPEAT OF CHILLY TEMPERATURES BY DAYBREAK MONDAY. MOST GUIDANCE FROM THE 12Z RUN SEEMS TOO WARM BASED ON THE LOWS THAT OCCURRED UNDER SIMILAR CONDITIONS LAST NIGHT...SO WILL BE USING MOS GUIDANCE FOR TONIGHT WHICH IS NOTABLY COOLER THAN OTHER SOLUTIONS. EXPECT UPPER 50S/LOWER 60S EAST OF THE BLUE RIDGE WITH LOW/MID 50S WEST AND SOME COOLER READINGS IN THE COLDEST VALLEYS. ALSO EXPECT SOME VALLEY FOG TO DEVELOP WEST OF THE BLUE RIDGE AND BECOME LOCALLY DENSE NEAR THE RIVERS BY DAYBREAK. THE REGION WILL BE GETTING SQUEEZED BETWEEN SYSTEMS ON MONDAY AS A COLD FRONT APPROACHES FROM THE NORTHWEST AND A TROF/FRONTAL BOUNDARY TO OUR SOUTHEAST GETS A PUSH BACK IN OUR DIRECTION AS LOW PRESSURE DEVELOPS OVER THE CAROLINAS. BEST CHANCE FOR ORGANIZED STORMS WILL BE WITH BETTER DYNAMICS OUTSIDE OF OUR AREA TO THE NORTH AND TIMING OF FRONT IS LATE SO SLGT/LOW CHANCE POPS FOR A LATE DAY THUNDERSTORM ACROSS SOUTHEAST WV SHOULD BE SUFFICIENT. SWLY FLOW EAST OF THE BLUE RIDGE WILL ALLOW FOR HIGHER DEWPOINTS TO MOVE IN AND HELP GENERATE SOME INSTABILITY DURING THE AFTERNOON. WHILE THE OVERALL ENVIRONMENT FEATURES WEAK DYNAMICS...OROGRAPHIC FORCING JUST EAST OF THE RIDGE COMBINED WITH CONVERGENCE ASSOCIATED WITH THE TROF/FRONTAL BOUNDARY WILL BE ENOUGH TO JUSTIFY MORE SLGT/LOW CHC POPS FOR A THUNDERSTORM TO THE EAST. THE END RESULT WILL BE DRY EARLY WITH THE CHANCE FOR A LATE DAY THUNDERSTORM MAINLY EAST OF THE BLUE RIDGE AND ACROSS SOUTHEAST WV. IT WILL ALSO BE WARMER AS TEMPERATURES REBOUND INTO THE LOWER 90S EAST WITH GENERALLY MID 80S WEST. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 230 PM EDT SUNDAY... LINGERING UPPER TROUGH WELL TO THE NORTH WILL SWING ANOTHER COLD FRONT TOWARD THE REGION FROM THE NW MONDAY NIGHT WITH THIS BOUNDARY BASICALLY JUMPING TO THE EASTERN LEE TROUGH ON TUESDAY. FRONT LIKELY TO BE PRECEDED BY A BROKEN BAND OF CONVECTION JUST NW OF THE CWA EARLY MONDAY EVENING BEFORE LIKELY SPLITTING/WEAKENING UPON CROSSING THE WESTERN RIDGES INTO DRIER AIR DURING LOSS OF HEATING. HOWEVER WITH GUIDANCE SHOWING SOME LEFTOVER INSTABILITY NW COUNTIES AND POTENTIAL FOR MOMENTUM TO CARRY CONVECTION A BIT FARTHER TO THE SE PENDING ORGANIZATION...INCLUDING SOME LOW CHANCE POPS NW THIRD TUESDAY NIGHT BUT DRY ELSEWHERE. GUIDANCE SHOWING MUCH OF THE AREA IN A SUBSIDENCE REGION TUESDAY INTO TUESDAY NIGHT ALONG/BEHIND THE FRONT AIDED BY DEEP WESTERLY FLOW AND LITTLE FOCUS. CANT TOTALLY RULE OUT ISOLATED SHRA/TSRA FAR WEST/SW WITH THE LOW LEVEL CONVERGENT FLOW AND HIGHER THETA-E...AS WELL AS THE FAR EASTERN PERIMETER WHERE WILL BE CLOSER TO THE BETTER INSTABILITY NEAR THE LEE TROUGH. THIS AREA ALSO WHERE MAY BE FAR ENOUGH REMOVED FROM DOWNSLOPING AND BETTER MIXING IN THE EVENING TO POP A SHOWER OR TWO SO RUNNING WITH 20ISH POPS IN THESE LOCATIONS. OTRW PARTLY/MOSTLY SUNNY BUT QUITE WARM/HOT VIA COMPRESSION TUESDAY WITH HIGHS MID/UPPER 80S WEST AND LOW/MID 90S EAST. NEXT RATHER STRONG SHORTWAVE WILL APPROACH FROM THE MIDWEST WEDNESDAY AND ATTEMPT TO LIFT THE BOUNDARY BACK NORTH THROUGH THE REGION WEDNESDAY NIGHT AS WARM FRONT AS THE WAVE PASSES TO THE NW. BEST INSTABILITY AND DEEPER MOISTURE WILL BE OVER THE FAR WEST LATER WEDNESDAY WITH MORE OVERRUNNING OF THE FRONT POSSIBLE WEDNESDAY NIGHT PENDING JUST HOW FAR WEST THIS WAVE ENDS UP TRACKING. LATEST MODELS SUGGEST COULD BE TOO FAR REMOVED FOR MUCH MORE THAN MID RANGE CHANCE POPS FAR NORTH-WEST FROM LATER WEDNESDAY INTO WEDNESDAY NIGHT WITH LACK OF DEEP CONVECTION PER ONLY WEAK LIFT/INSTABILITY. HOWEVER FOR NOW WILL LEAVE IN SOME CHANCES ACROSS THE REGION AND SEE HOW LATER RUNS EVOLVE GIVEN SUCH UNCERTAINTY. SHOULD AGAIN BE QUITE WARM/MUGGY WEDNESDAY WITH THE 850 MB BOUNDARY SLIDING BACK NORTH ALLOWING MORE OF A SW TRAJECTORY WHICH SHOULD AT LEAST HOLD HIGHS A CATEGORY OR SO BELOW VALUES SEEN ON TUESDAY. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 1245 PM EDT SUNDAY... TRANSITION TO MORE ZONAL FLOW ALOFT WILL OCCUR EARLY IN THE PERIOD AS THE REGION GETS CAUGHT UNDER THE SURFACE-850 MB BAROCLINIC ZONE AND WITHIN A NEARBY FRONTAL ZONE STRETCHED BACK INTO THE MIDWEST. A COUPLE OF SHORTWAVES RIDING ALONG THESE FEATURES TO AID CONVECTIVE CHANCES...ESPCLY NORTH/WEST THURSDAY INTO THURSDAY NIGHT AS DECENT LOW PRESSURE PASSES JUST NORTH...SUPPORTIVE OF HIGH CHANCE/LOW LIKELY POPS. STRONGER ENERGY ALOFT DROPPING OVER THE CENTRAL STATES UPPER RIDGE WILL THEN START TO DIG OUT ANOTHER RATHER STRONG 5H TROUGH TO THE NW FRIDAY...WITH AN ASSOCIATED SURFACE WAVE HELPING TO DRIVE THE NEXT COLD FRONT THROUGH THE REGION BY FRIDAY EVENING. EARLIER MODELS AGREED ON QUITE A BIT OF DEEP MOISTURE BEING PULLED NORTH AHEAD OF THE FRONT/WAVE ON FRIDAY WITH GOOD DYNAMICS AND JET FEATURES ALOFT. THIS WOULD SUPPORT MORE WIDESPREAD SHOWERS/STORMS FRIDAY UNLESS THE FRONT IS FASTER SIMILAR TO THE LATEST GFS WHICH WOULD TREND THE BEST COVERAGE THURSDAY INTO THURSDAY NIGHT. THUS HAVE TRENDED THE HIGHEST CHANCE TO LIKELY POPS LATE THURSDAY INTO THURSDAY NIGHT WHILE KEEPING HIGH CHANCES FRIDAY FOR CONSISTENCY AND LINE WITH THE CURRENT CMC AND EARLIER ECMWF. WILL BE A BIT COOLER BUT STILL HUMID PER MORE CLOUDS/SHRA WITH HIGHS MOSTLY 80S THURSDAY... LOWERING TO 70S WEST TO MID 80S EAST FRIDAY. SIMILAR TO THE LAST WEEK OR TWO...APPEARS ANOTHER SURGE OF MUCH DRIER/COOLER AIR LIKELY BEHIND THE FRONT NEXT WEEKEND AS YET ANOTHER 5H TROUGH CARVES ITSELF OUT ACROSS THE EAST. GUIDANCE EVEN COOLER ALOFT WITH THIS SYSTEM GIVEN PROGGED 850 MB TEMPS AS COOL AS +12C MOUNTAINS BUT MAY BE TOO COOL THAT FAR OUT. HOWEVER STILL ENOUGH TO DROP HIGHS BACK IN THE 70S MOUNTAINS AND ONLY LOW/MID 80S OUT EAST AS HIGH PRESSURE BUILDS/WEDGES IN FROM THE NORTH. RESIDUAL POPS A BIT TRICKY TOWARD DAYS 6/7 BUT SHOULD BE DRIER WITH PERHAPS SOME LEFTOVER UPSLOPE SHOWERS WEST SATURDAY AND ONLY ISOLATED FAR SOUTHWEST ON SUNDAY. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... AS OF 745 PM EDT SUNDAY... GENERALLY VFR CONDITIONS EXPECTED THROUGH THE TAF VALID PERIOD AS A RELATIVELY DRY AIR MASS REMAINS OVER THE REGION. LOW-LEVEL MOISTURE WILL SLOWLY BE INCREASING THROUGH THE PERIOD ON THE HEELS OF SOUTHWEST FLOW EXPECTED TO EVOLVE MORE EARNESTLY ACROSS THE REGION MONDAY AS SFC HIGH PRESSURE DRIFTS TO THE SOUTHEAST OF THE REGION AND A TROUGH OF LOW PRESSURE TRACKS EASTWARD THROUGH THE GREAT LAKES. AN ASSOCIATED FRONTAL BOUNDARY WILL BE APPROACHING FROM THE NORTHWEST LATE IN THE DAY. CONVECTION IS EXPECTED TO ACCOMPANY THE FRONT INTO EASTERN KY...FAR WESTERN WV...BEFORE DISSIPATING AS THE ACTIVITY ATTEMPTS TO CROSS THE MOUNTAINS DURING THE EVENING AND INTO A MUCH MORE STABLE AIR MASS IN OUR REGION. HAVE NOT ADVERTISED ANY PRECIPITATION THIS TAF VALID PERIOD. FOG CONCERNS ARE MINIMAL AS AIR MASS IS VERY DRY. HOWEVER...AS IS OFTEN THE CASE FOR LWB IN THE GREENBRIER VALLEY...RADIATIONAL COOLING SHOULD SUPPORT FOG DEVELOPMENT LATE TONIGHT/EARLY MONDAY MORNING AND THUS HAVE ADVERTISED A PERIOD OF 1/4SM FG VV001. ELSEWHERE...CONFIDENCE IN ANY FOG IS LOW...PERHAPS A PERIOD OF MVFR BR AND BCB/LYH. WINDS...MOSTLY CALM OVERNIGHT...BECOMING SOUTHWEST MONDAY MID- MORNING AND INCREASING INTO THE 7-8KT RANGE MOST SITES BY LATE MORNING. SOME LOW END GUSTS POSSIBLE BLF AND ROA...BUT HAVE NOT INCLUDED THOSE IN THE TAF JUST YET. HIGH 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 FORECAST... MOSTLY VFR OUTSIDE OF ANY CONVECTION THROUGH THE PERIOD. A FRONT WILL SET UP IN THE MID ATLANTIC WHICH COULD BRING A FEW SHRA/TSRA BY TUESDAY...WITH PERHAPS A BIT MORE COVERAGE LATER WEDNESDAY AT THIS POINT. THUS THE THREAT OF SUB-VFR REMAINS LOW UNTIL AROUND MIDWEEK...EXCEPT FOR THE TYPICAL FOG POTENTIAL AT KLWB/KBCB EACH MORNING BETWEEN 09-13Z. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...DS/MBS SHORT TERM...JH LONG TERM...JH AVIATION...MBS/RAB

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