Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 272246 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 646 PM EDT SUN JUL 27 2014 .SYNOPSIS... UPPER DISTURBANCES WILL CONTINUE TO WORK ACROSS THE AREA THIS EVENING IN ADVANCE OF A STRONG COLD FRONT THAT WILL BE ARRIVING FROM THE NORTHWEST AFTER MIDNIGHT. THESE FEATURES MAY TRIGGER STRONG TO POTENTIALLY SEVERE THUNDERSTORMS INTO EARLY TONIGHT. THE COLD FRONT WILL MOVE ACROSS THE REGION BY EARLY MONDAY...RESULTING IN COOLER WEATHER INTO THE MIDDLE OF THE WORK WEEK. && .NEAR TERM /THROUGH MONDAY/... AS OF 645 PM EDT SUNDAY... TORNADO WATCH 448 ISSUED FOR A SMALL PART OF SW VA AND MOST OF OUR NW NC COUNTIES UNTIL 1 AM EDT. NOT ENTIRELY CONFIDENT THAT MUCH OF THE CWA WILL SEE SEVERE THREAT...SO IN DISCUSSION WITH SPC AM HOLDING OFF ON ANY FURTHER WATCHES UNTIL WE SEE IF ONE IS NEEDED FURTHER EAST ACROSS THE PIEDMONT. TIMING OF FRONT SUGGESTS THAT WE SHOULD BE ABLE TO CANCEL MUCH...IF NOT ALL OF THIS WATCH 448...BEFORE 1 AM EDT. NO OTHER SIGNIFICANT CHANGES TO THE ZONES AT THIS TIME AS POP AND TEMP TRENDS LOOK GOOD. AS OF 200 PM EDT SUNDAY... EXTENSIVE CLOUD SHIELD IN THE WAKE OF THE EARLIER IMPULSE SLOWLY ERODING IN SPOTS MAINLY SOUTH AND EAST BUT HAS ACTED TO KEEP A LID ON INSTABILITY SO FAR GIVEN OVERALL LACK OF HEATING. THIS EVIDENCED VIA THE SPECIAL 18Z SOUNDING WHICH SHOWS QUITE A CAP ALOFT WHICH WILL TAKE A LOT MORE HEATING OR DYNAMICS LATER TO OVERCOME. OTRW NEXT MCS INDUCED WAVE ROLLING SE OUT OF KY THE MAIN PLAYER INTO LATE AFTERNOON/EARLY THIS EVENING AS IT JETS SE IN ADVANCE OF THE UPSTREAM COLD FRONT CURRENTLY BACK IN THE MIDWEST. LATEST GUIDANCE CONTINUES TO NOT HANDLE THE ONGOING SCENARIO VERY WELL...ALTHOUGH THE LATEST NSSL WRF TAKES THIS CONVECTION SE INTO OUR FAR SW COUNTIES WHERE GUIDANCE SHOWS BETTER THETA-E RIDGING AND SOMEWHAT BETTER LOW LEVEL THERMODYNAMIC SUPPORT WITHIN A BETTER SW JET ALOFT. OTHER AREA TO WATCH WILL BE OVER THE FAR WEST THIS EVENING INTO EARLY TONIGHT AS THE ACTUAL COLD FRONT AND UPPER COLD POOL DYNAMICS ARRIVE ACROSS THE FAR WEST. HOWEVER WINDS WILL BE VEERING MORE WESTERLY BY THEN AND ANY INSTABILITY WANING WHICH SHOULD PUT THE BEST FOCUS ALONG THE WESTERN SLOPES WHERE MODEL CONSENSUS HAS THE BETTER COVERAGE. THIS ACTIVITY LIKELY TO HAVE A HARD TIME SPILLING EAST BUT KEPT IN CHANCE POPS THROUGH THE EVENING EAST WHILE GOING LIKELYS TO LOW END CAT FAR WEST EARLY ON. 85H FRONT WILL FINALLY SURGE ACROSS THE MOUNTAINS AFTER MIDNIGHT...REACHING THE PIEDMONT TOWARD DAYBREAK MONDAY. MUCH DRIER AIR ARRIVING ALOFT SHOULD CUT INTO ANY LEFTOVER SHRA COVERAGE WITH ONLY SOME LOW CLOUDS AND SPOTTY SHOWERS REMAINING IN THE UPSLOPE REGIONS OVERNIGHT. WINDS WILL TURN GUSTY ON THE RIDGES FROM THE NW BEHIND THE FRONT BUT SHOULD REMAIN BELOW ANY ADVISORY LEVELS ALTHOUGH QUITE BLUSTERY FOR LATE SUMMER. KEPT LOWS MORE IN LINE WITH THE WARMER MET MOS EAST AND TOOK A BLEND WEST WHERE COOL ADVECTION MAY BE OFFSET BY MIXING. 5H TROF CROSSES EAST OF THE AREA MONDAY ALLOWING HIGH PRESSURE TO START BUILDING IN FROM THE WEST DURING THE AFTERNOON. HOWEVER ANOTHER SHORTWAVE ROUNDING DOWN THE BACK OF THE COOL POOL MAY HELP TO ENHANCE THE SHOWERS AS IT COINCIDES WITH THE COLDEST 85H TEMPS AND MAX HEATING. THUS BOOSTED POPS WESTERN SLOPES TO A PERIOD OF LOW LIKELYS MONDAY AFTERNOON WITH A QUICK CUTOFF TO SHRA BLUE RIDGE AND POINTS EAST WHERE DOWNSLOPING SHOULD ALLOW FOR LESS CLOUDS. OTRW WILL BE A BREEZY AND COOL DAY FOR LATE JULY OVER THE MOUNTAINS WHERE MAY STRUGGLE TO GET OUT OF THE 60S WHERE CLOUDS PERSIST AND ALONG HIGHER ELEVATIONS. SHOULD BE ABLE TO GET WELL INTO THE 80S UNDER DRY DOWNSLOPE PIEDMONT BUT ONLY 75-82 BLUE RIDGE. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 215 PM EDT SATURDAY... WEST TO NORTHWEST UPPER FLOW WILL PERSIST OVER THE BLACKSBURG FORECAST AREA THROUGH THE SHORT TERM PERIOD AS SERIES OF WEAK SHORT WAVE TROFS EMBEDDED IN UPPER FLOW HELP ANCHOR PIN-WHEELING UPPER TROF OVER THE GREAT LAKES. COOLER AIR ALOFT...WEAK FORCING FROM INITIAL SHORT WAVE...AND WEAK UPSLOPING MAY SUPPORT ISOLATED TO WIDELY SCATTERED SHOWERS ACROSS THE WESTERN FLANKS OF THE APPALACHIANS ON MONDAY NIGHT...AND PERHAPS DIURNALLY DRIVEN EVEN INTO TUESDAY. HOWEVER...DESPITE ADDITIONAL WEAK STREAM ENERGY...ARRIVAL OF SURFACE RIDGE AND AMPLIFICATION OF SUBSIDENCE INVERSION SHOULD BE SUFFICIENT TO LIMIT THREAT FOR ANY ADDITIONAL SHOWER ACTIVITY TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. UPSLOPING CLOUDS ACROSS THE WEST SHOULD MAINTAIN UNSEASONABLY COOL TEMPERATURES IN THE MOUNTAINS...WITH DAYTIME HIGHS NOT LIKELY TO CLIMB OUT OF THE 60S ON EITHER TUESDAY OR WEDNESDAY ACROSS THE HIGHEST TERRAIN. EAST OF THE BLUE RIDGE...ANY INFLUENCE OF COLD ADVECTION WILL BE OFFSET BY DOWNSLOPING/COMPRESSIONAL HEATING AND GOOD INSOLATION SUCH THAT HIGHS REACH INTO THE LOWER TO MID 80S...YET STILL ~5F LOWER THAN CLIMATOLOGICAL AVERAGES. NIGHTTIME LOWS WILL BE LARGELY GOVERNED BY EXTENT OF MIXING AND CLOUD COVER. HIGHER ELEVATIONS WHERE/IF CLOUDS CAN CLEAR...AND ESPECIALLY THE MOUNTAIN VALLEYS WHERE BOUNDARY LAYER DECOUPLING WILL MORE READILY OCCUR...SHOULD EXPERIENCE AT LEAST SPOTTY READINGS DOWN INTO THE 40S. READINGS EAST OF THE BLUE RIDGE WILL BE A BIT MILDER...MAINLY 50S...YET STILL 5-10F BELOW CLIMATOLOGICAL AVERAGES. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 1200 PM EDT SUNDAY... A SURFACE HIGH THURSDAY OVER SOUTHERN MICHIGAN WILL SHIFT EAST TOWARDS NEW ENGLAND BY FRIDAY AND SATURDAY. AT THE MID LEVELS A PERSISTENT TROUGH IS SET UP OVER THE EASTERN US WITH A RIDGE OVER THE WESTERN US. THURSDAY LACKS LOW AND MID LEVEL MOISTURE SO EXPECT THE DAY TO BE DRY. MOISTURE AND INSTABILITY INCREASE FOR FRIDAY AND THROUGH THE REST OF THE PERIOD AS SEVERAL DISTURBANCES PIVOT ACROSS THE REGION AROUND THE BASE OF THE TROUGH. EXPECT SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP EACH AFTERNOON/EVENING AND TAPER OFF TO JUST SCATTERED SHOWERS DURING THE EVENING. FOCUS OF THE HIGHEST CHANCE POPS ARE OVER THE MOUNTAINS WHERE THE BEST CONVERGENCE WILL BE LOCATED...WITH LOWER CHANCE POPS OUT EAST. THURSDAY WILL BE THE WARMEST DAY OF THE PERIOD WITH 850MB TEMPS AROUND +16C. THIS WILL CORRESPOND TO SURFACE HIGH TEMPS IN THE MID 80S OUT EAST AND NEAR 80 ACROSS THE MOUNTAINS. AS THE HIGH SHIFTS EAST ON FRIDAY THE WINDS WILL SHIFT FROM N/NW TO AN EASTERLY DIRECTION. THIS WILL WEDGE THE AREA IN THROUGH THE REMAINDER OF THE PERIOD. WITH THE INCREASED LOW/MID LEVEL MOISTURE EXPECT CLOUDY CONDITIONS. THIS ALONG WITH EXPECTED SCATTERED PRECIP AND 850MB TEMPS FALLING TO +11-14C...SURFACE HIGH TEMPS WILL BE 5-10 DEGREES BELOW NORMAL FRIDAY THROUGH SUNDAY. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... AS OF 1235 PM EDT SUNDAY... BAND OF SHALLOW CONVECTION CONTINUES TO WORK EAST OF THE BLUE RIDGE AND SHOULD EXIT THE KLYH AREA IN THE NEXT HOUR. ONCE THIS PASSES...MOST AREAS WILL START TO SEE CIGS GRADUALLY LIFT ALLOWING A PERIOD OF VFR ACROSS THE REGION INTO MID AFTERNOON...AND PERHAPS LONGER ACROSS THE EASTERN SITES. CONFIDENCE NOW LOWER IN REGARDS TO THE DEGREE OF WIDESPREAD ADDITIONAL CONVECTION THAT WILL DEVELOP TO THE WEST AND PUSH EAST ACROSS THE AREA INTO THIS EVENING. COMBO OF RESIDUAL CLOUD COVER AND BEST SUPPORT BEING WELL TO THE WEST SUGGESTS WILL SEE MORE SCATTERED SHRA/TSRA WITH THE BETTER CONCENTRATION ALONG THE WESTERN SLOPES FROM KBLF TO KLWB ONCE THEY BECOME MORE UNSTABLE LATER THIS AFTERNOON. THUS WILL GOING WITH MORE MVFR IN PREVAILING SHRA/TSRA AT THESE SPOTS...AND VICINITY MENTION WITH EMBEDDED TEMPO GROUPS FOR STRONGER STORMS ELSW INTO EARLY THIS EVENING. A COLD FRONT PASSES LATER TONIGHT...LEAVING VFR CONDITIONS FROM THE BLUE RIDGE EAST AND LINGERING MVFR WITH UPSLOPE FLOW IN THE FAR WEST WHERE A FEW SHOWERS MAY ALSO LINGER. WINDS TURN GUSTY FROM THE NORTHWEST BEHIND THE FRONT AFTER MIDNIGHT INTO EARLY MONDAY WITH GUSTS PERHAPS REACHING 25-30 KTS AT TIMES LATE. EXTENDED AVIATION DISCUSSION... THREAT OF SUB VFR THROUGH MONDAY OR MONDAY NIGHT EXPECTED ACROSS SE WEST VA PER NW FLOW...BUT LESS ELSEWHERE GIVEN DOWNSLOPE. PERIODIC SHOWERS MAY ALSO DEVELOP ALONG THE NW SLOPES ESPCLY MONDAY AFTERNOON BUT GIVEN ISOLATED NATURE WILL LEAVE OUT MENTION FOR NOW. DRIER AIR PUSHING IN FOR TUESDAY-WEDNESDAY WILL BRING MAINLY VFR CONDITIONS...BUT CANNOT RULE OUT LATE NIGHT FOG KBCB/KLWB ALTHOUGH THE LOW LEVELS MAY STAY DRY ENOUGH FOR LESS FOG COVERAGE. VARIABLE CIGS EXPECTED UNDER ANOMALOUS UPPER LOW THROUGHOUT THE REST OF THE WEEK. A FEW -SHRA NOT COMPLETELY OUT OF THE QUESTION ACROSS EASTERN WV...ALONG WITH OCCASIONAL MVFR CIGS. TYPICAL FOG POTENTIAL LESS THAN NORMAL FOR THIS TIME OF YEAR THROUGHOUT THE WEEK BECAUSE OF TURBULENT MIXING AND PREVAILING CYCLONIC FLOW. TOWARD THE END OF THE WEEK...AS THE UPPER LOW RETROGRADES JUST WEST OF THE REGION...INCREASING POTENTIAL FOR SHRA/TSRA BUT MAINLY SW OF THE TAF SITES INTO FRIDAY. && .EQUIPMENT... THE WEATHER RADIO AT HINTON WEST VA TRANSMITTING ON FREQUENCY 162.425 MHZ REMAINS OFF THE AIR LIKELY DUE TO PHONE LINE PROBLEMS. TECHNICIANS ARE WORKING ON THE PROBLEM BUT TIME OF RESTORATION REMAINS UNKNOWN AT THIS TIME. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/NF NEAR TERM...JH/RAB SHORT TERM...WERT LONG TERM...CF AVIATION...JH/PH EQUIPMENT...JH

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