Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 011747 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 147 PM EDT WED JUL 1 2015 .SYNOPSIS... A FRONTAL ZONE WILL REMAIN DRAPED ACROSS THE AREA FOR THE NEXT SEVERAL DAYS. WAVES MOVING ALONG THIS FRONTAL ZONE WILL KEEP A CHANCE OF SHOWERS AND THUNDERSTORMS IN OUR FORECAST THROUGH THE WEEKEND. HIGH PRESSURE MOVING IN FROM THE UPPER MIDWEST ON SUNDAY MAY FINALLY NUDGE THE FRONT FAR ENOUGH TO OUR SOUTH AND EAST TO BRING SOME DRIER WEATHER TO THE REGION FOR THE FIRST PART OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF NOON EDT WEDNESDAY... MODIFIED MORNING SOUNDING SUGGESTS SBCAPE OF 1200 J/KG THIS AFTERNOON OVER THE REGION. FORECAST AREA REMAINS IN A LULL BETWEEN UPPER WAVES. HAD A FEW SHOWERS MOVE NORTH OF GREENBRIER COUNTY THIS MORNING...AND RADAR IS NOW CLEAR OF PRECIP. HIGH-RES AND 12Z NAM SUGGEST THE DEVELOPMENT OF SHOWERS AND STORMS EAST OF THE BLUE RIDGE BY EARLY AFTERNOON...WITH LITTLE OR NONE BETWEEN THE BLUE RIDGE AND THE WV/VA/ BORDER...WITH MORE ACTIVITY ARRIVING/DEVELOPING OVER THE MTN EMPIRE INTO THE NC MTNS MID AFTERNOON...AS UPSTREAM WAVE AND MCS OVER WRN TN MOVES SE TOWARD THE SOUTHERN APPALACHIANS. ADJUSTED POPS TO LOWER IN THE NORTH AND CENTRAL PART OF THE FORECAST AREA INTO THE PIEDMONT WITH LOW/SLIGHT CHANCE AT BEST. KEPT HIGHER POPS OVER THE MTN EMPIRE INTO THE NC MTNS THOUGH. HIGH TEMPS WILL BE STILL BE WARM/NEAR NORMAL FROM NEAR 90 SOUTHEAST TO UPPER 70S/LOWER 80S WEST. PREVIOUS VALID DISCUSSION... AN UPPER LEVEL TROF WILL REMAIN OVER THE EASTERN US AS IMPULSES OF SHORT WAVE ENERGY ROTATE THROUGH THE FLOW. THIS WILL DRIVE A LOW PRESSURE SYSTEM FROM THE GREAT LAKES REGION IN TO CANADA AND KEEP A FRONTAL ZONE MEANDERING ACROSS THE REGION. BELIEVE ACTIVITY WILL START TO TAPER OFF AFTER SUNSET...BUT MODEL GUIDANCE IS KEEN ON THE IDEA OF SLIDING ANOTHER IMPULSE ALONG THE FRONTAL ZONE AND INTO THE AREA LATE TONIGHT. WHILE WATER VAPOR IMAGERY DOES INDEED SUPPORT THE NOTION OF A SERIES OF SHORT WAVES...CONFIDENCE IS LOW AS TO WHETHER OR NOT ONE OF THESE WILL KICK OFF AN MCS THAT WILL BRING WIDESPREAD SHOWERS/THUNDER TO THE REGION TONIGHT. FOR NOW WILL GO WITH A WETTER SOLUTIONS AND RAISE POPS BACK UP TO HIGH CHC/LOW LIKELY WEST OF THE BLUE RIDGE IN ANTICIPATION OF AN MCS REMNANT MOVING IN. WILL HAVE TO TAKE A LOOK AT THE MESO MODELS LATER TODAY TO SEE IF THESE POPS CONTINUE TO LOOK VALID. EXPECTING TEMPS TO BE RIGHT AROUND NORMAL WITH READINGS UPPER 60S EAST/LOWER 60S WEST FOR LOWS TONIGHT. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... AS OF 415 AM EDT WEDNESDAY... BROAD TROUGHING CONTINUES THROUGH THE PERIOD WITH NUMEROUS EMBEDDED DISTURBANCES TRACKING THROUGH THE BASE OF THE TROUGH ROUGHLY ON A PERSISTENT TRAJECTORY FROM THE NORTHERN PLAINS SOUTHEASTWARD THROUGH THE MO/TN VALLEY INTO THE SOUTHERN APPALACHIANS AND SOUTHEAST STATES. THIS PATTERN WILL CERTAINLY SUPPORT CONTINUED MESOSCALE CONVECTIVE COMPLEXES AS IT HAS THE PAST COUPLE OF DAYS. HOWEVER...THERE ARE SUBTLE DIFFERENCES AMONG THE MODELS AS TO THE EXACT TRACK AND TIMING OF THE PROJECTED MESOSCALE CONVECTIVE...WHICH LEADS TO LOW CONFIDENCE IN THE POP FORECAST AND TO A LESSER EXTENT THE TEMPERATURE FORECAST. IN ADDITION...MODELS PROJECT ASSOCIATED RAINFALL/QPF AT ALL HOURS OF THE DAY AND NIGHT...WHICH IS MOST LIKELY NOT THE SCENARIO THAT WILL PLAY OUT. GIVEN THE TIME OF YEAR...DIURNAL HEATING AND THE NORMAL DIURNAL CYCLE OF PRECIPITATION CAN BE EXPECTED DESPITE THE MODEL PROJECTIONS. IT DOES APPEAR MORE LIKELY THAT THE SOUTHWEST PART OF THE CWA HAS A BETTER CHANCE OF SEEING REPEATED MCS ACTIVITY THROUGH THE PERIOD THAN DOES THE NORTHEAST...BUT A SLIGHT CHANGE IN THE PATH/TIMING WOULD RENDER THIS THEORY LESS ACCURATE. OVERALL...THERE IS A TENDENCY FOR THE BAROCLINIC ZONE TO SHIFT SOUTH MORE INTO AL/GA/SC BY THE WEEKEND. AT THIS POINT...THE BEST DYNAMICS AND INSTABILITY APPEAR TO TRACK ACROSS THE REGION FRIDAY...WHICH CORRESPONDS WITH THE ONLY PERIOD IN WHICH SPC CURRENTLY HAS MORE THAN JUST A TINY CORNER OF THE CWA IN A MARGINAL RISK. BOTH THURSDAY AND FRIDAY THERE APPEARS TO BE SOME CHANCE FOR A REMNANT MCS TO BE DRIFTING INTO THE REGION AT DAYBREAK...WHICH LEAVES CONSIDERABLE QUESTION AS TO HOW MUCH INSTABILITY AND REDEVELOPMENT OF CONVECTION WILL TAKE PLACE LATER IN THE DAY IF CLOUD COVER...PRECIPITATION...AND COOLER TEMPERATURES LINGER. INSTABILITY PROGS ARE MEAGER AT BEST THROUGH MUCH OF THE PERIOD AND THE BEST SHEAR AXIS REMAINS TO OUR SOUTHWEST. SO OVERALL...CONFIDENCE IS QUITE LOW IN THE POP FORECAST OTHER THAN TO SAY THAT PRECIPITATION AND CONVECTION IS LIKELY WITHIN AT LEAST 12 HOUR BLOCKS EACH DAY. TRACK AND TIMING WILL ONLY BE POSSIBLE AS THESE EVENTS MOVE INTO THE NEAR TERM. FOR THIS REASON...HAVE GENERALLY CAPPED POPS IN THE 50-60 PERCENT RANGE DAYTIME AND 30-40 PERCENT RANGE NIGHTTIME...WITH THE HIGHEST POPS THROUGH MUCH OF THE TIME FRAME FOCUSED ACROSS THE SOUTHWEST...MORE LIKELY TO BE WITHIN THE PATH OF PROJECTED CONVECTIVE COMPLEXES. 850MB TEMPS HOVER IN THE +12C TO +16C RANGE NORTH TO SOUTH THROUGH MOST OF THE PERIOD. THIS...COMBINED WITH THE EXPECTED CLOUD COVER AND PRECIPITATION WILL HOLD MAX TEMPS SLIGHTLY BELOW NORMAL...BUT MIN TEMPS ABOVE NORMAL. && .LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 430 AM EDT WEDNESDAY... THE PERSISTENT UPPER TROUGH DURING THE SHORT TERM PERIOD BEGINS TO SHEAR OUT AND LIFT NORTHEAST DURING THE LONG TERM AS UPPER HEIGHTS BEGIN TO RISE IN RESPONSE TO BROAD UPPER RIDGING EXTENDING FROM THE SOUTHWEST/SOUTH CENTRAL U.S. INTO THE NORTHEAST U.S. THE TAIL END OF THE PRIOR UPPER TROUGH APPEARS DESTINED TO BECOME CUTOFF ACROSS THE SOUTHEAST STATES. THIS PERIOD SHOULD BE CHARACTERIZED BY A GENERAL DECREASE IN CONVECTION...CERTAINLY LESS MCS ACTIVITY AS THE PATTERN BECOMES CONSIDERABLY LESS FAVORABLE FOR SUCH THROUGH THE PERIOD...AND A SLIGHT INCREASE IN TEMPERATURES. THE INCREASE IN MAX TEMPS...ESPECIALLY...WILL BE A RESULT OF THE ENHANCED UPPER RIDGING...500MB HEIGHTS RISING INTO THE 588-590DM RANGE AND INEVITABLY POCKETS OF 850MB TEMPS +20C TO +21C APPEARING...ESPECIALLY ACROSS THE PIEDMONT. THIS WILL ALLOW SOME MAX TEMPS IN THE LOW 90S TO REAPPEAR ACROSS THE SOUTHEAST...E.G. KDAN. ALTHOUGH HEIGHTS ARE RISING AND THERE IS LESS POTENTIAL FOR MESOSCALE COMPLEXES...WEAK NORTHWEST FLOW ALOFT PERSISTS AND WILL STILL SUPPORT A THREAT FOR CONVECTION. HOWEVER...POPS MORE IN THE 20-40 PERCENT RANGE APPEAR MORE REASONABLE DURING THIS PERIOD THAN THE 50-60 POPS ADVERTISED THROUGH MUCH OF THE SHORT TERM. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 135 PM EDT WEDNESDAY... HAVE VFR THROUGH THE AFTERNOON WITH LIMITED CONVECTION. HIGH-RES MODELS ARE FAVORING SHOWERS AND STORMS TO FORM BETWEEN LYH/DAN BUT THE CONFIDENCE IS LOW TO EVEN ADD VCTS AT THOSE TERMINALS. TOWARD EVENING THERE IS A POTENTIAL CONVECTION NOW OVER TN/KY TO MOVE INTO BLF/TRI AREA...AND THIS WILL BE MAINLY AFTER 21Z...SO HAVE VCTS AT BLF. MODELS SHOW THIS ACTIVITY INCREASING TONIGHT WITH MORE OF A SRN CWA TRACK...WHERE LYH/ROA MAY NOT SEE ANYTHING...BUT ENOUGH CONFIDENCE TO HAVE PREDOMINANT SHRA AT BLF/LWB/BCB LATE. GIVEN MORE CLOUDS THINK THE FOG THREAT WILL BE LIMITED...SO KEPT IT MORE IFR/MVFR. WINDS WILL BE ON THE LIGHT SIDE WITH SOME LOW END GUSTS EARLY THIS AFTERNOON. EXTENDED AVIATION DISCUSSION... THE REGION WILL BE IN A GENERAL NORTHWEST FLOW PATTERN THROUGH SATURDAY. WHILE ISOLATED TO SCATTERED SHOWERS AND STORMS CANNOT BE RULE OUT ANY OF THESE DAYS...THE BEST POTENTIAL WILL BE ON THURSDAY...THEN AGAIN LATER FRIDAY...FOLLOWED BY A THIRD POTENTIAL INCREASE IN COVERAGE ON SATURDAY AS SEPARATE SHORTWAVE TROUGHS PROGRESS TROUGH THE NORTHWEST FLOW. VFR CONDITIONS ARE EXPECTED FOR MOST OF THE AREA MUCH OF THE TIME. THE EXCEPTIONS WILL COME AS TEMPORARY DECREASES WITHIN ANY HEAVIER RAIN SHOWERS OR THUNDERSTORMS...AND THEN LATE AT NIGHT AND EARLY MORNING DUE TO RIVER OR MOUNTAIN VALLEY FOG...ESPECIALLY IN AREAS THAT RECEIVED PRECIPITATION THE DAY BEFORE. SUNDAY INTO MONDAY HEIGHTS RISE BUT THERE REMAINS AN UPPER TROUGH MOVING OVER THE MID ATLANTIC DURING THIS TIME SO STORMS ARE NEVER OUT OF THE FORECAST. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...MBS NEAR TERM...MBS/WP SHORT TERM...RAB LONG TERM...RAB AVIATION...JM/WP

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