Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 050046 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 846 PM EDT TUE AUG 4 2015 .SYNOPSIS... A WEAK COLD FRONT WILL STALL ACROSS THE CAROLINAS WEDNESDAY. THIS WILL BRING A CHANCE OF SHOWERS AND THUNDERSTORMS TO OUR FORECAST THROUGH MIDWEEK. AN AREA OF LOW PRESSURE IS EXPECTED TO FORM ALONG THE FRONT THURSDAY AND MOVE NORTHEAST ACROSS THE MID ATLANTIC REGION FRIDAY... WITH A MUCH BETTER CHANCE FOR WIDESPREAD THUNDERSTORMS THROUGH THE END OF THE WORKWEEK. && .NEAR TERM /THROUGH WEDNESDAY/...
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AS OF 815 PM EDT TUESDAY... ISOLATED CONVECTION CONTINUES TO DEVELOP ALONG REMNANT OUTFLOW BOUNDARIES DRIFTING IN FROM THE WEST. HAVE TWICE MASSAGED POPS TO ADJUST TO THE LATEST TRENDS. CAPE/INSTABILITY REMAINS QUITE HIGH WITH TEMPERATURES STILL WELL IN THE 80S AND DEWPOINTS IN THE 60S TO LOW 70S AND THERE HAS BEEN NO GENERAL WORKOVER OF THE AREA TODAY FROM ANY WIDESPREAD CONVECTION. THUS...WOULD EXPECT ISOLD SHRA/TSRA TO CONTINUE TO POP UP ACROSS MUCH OF THE CWA THROUGH THE EVENING HOURS EVEN UP UNTIL MIDNIGHT. FURTHERMORE...A WEAK FRONTAL BOUNDARY/BAROCLINIC ZONE EXTENDS FROM SOUTHERN IL THROUGH KY/TN INTO NORTHERN NC. THIS WILL FURTHER SERVE TO AID IN ISOLD-SCT CONVECTION THROUGH THE EVENING. ADDITIONAL MODIFICATIONS WILL LIKELY BE REQUIRED THROUGH THE EVENING. TEMPERATURES AND DEWPOINTS WERE GENERALLY ON TRACK...WITH ONLY MINOR MODIFICATIONS MADE SOME MINOR ADJUSTMENTS TO CLOUD COVER. AS OF 330 PM EDT TUESDAY... CONVECTION HAS DEVELOPED AHEAD OF A COLD FRONT APPROACHING FROM THE NORTHWEST. THIS ACTIVITY WILL CONTINUE TO DEVELOP AND MOVE ACROSS THE REGION THIS EVENING WITH THE GREATEST COVERAGE OF STORMS EXPECTED TO BE EAST OF THE BLUE RIDGE WHERE THE INSTABILITY IS GREATEST. SEVERE PARAMETERS ARE MARGINAL SO EXPECT SOME STRONGER STORMS TO PULSE UP AND PRODUCE HAIL AND GUSTY WINDS. THIS ACTIVITY WILL TAPER OFF WITH THE LOSS OF HEATING AFTER SUNSET. THE FRONT WILL NOT PASS CLEANLY THROUGH THE REGION AND WILL SERVE AS A TRIGGER FOR ANOTHER ROUND OF SCATTERED THUNDERSTORMS TOMORROW AFTERNOON AS UPPER LEVEL SHORT WAVE ENERGY APPROACHES FROM THE WEST. INSTABILITY AND DYNAMICS ARE LIMITED TOMORROW SO EXPECTING GENERAL THUNDERSTORMS WITH A LOW SEVERE THREAT. TEMPERATURES WILL BE QUITE SIMILAR TO READINGS WE HAVE SEEN OF LATE WITH MINS TONIGHT AROUND 70 EAST OF THE RIDGE TO LOW/MID 60S WEST...AND HIGHS WEDNESDAY LOWER 90S EAST TO MIDDLE 80S WEST.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... AS OF 430 AM EDT TUESDAY... BY THURSDAY MORNING...SHORT WAVE WILL BE COMING OUT OF THE MID MISSISSIPPI VALLEY. THIS FEATURE WILL CROSS THE FORECAST AREA ON THURSDAY NIGHT. SURFACE TO 850 MB BACK TO THE SOUTH AND POSSIBLY THE SOUTHEAST ON THURSDAY AHEAD OF THE LOW PRESSURE SYSTEM TRACKING ALONG THE FRONT. THIS FLOW WOULD BE ADVECTING IN PRECIPITABLE WATER VALUES IN THE 1.5 TO 2.0 INCH RANGE. WILL BE INCREASING PROBABILITY OF PRECIPITATION AND FORECAST RAINFALL AMOUNTS. BY FRIDAY MORNING...THE LOW WILL BE OVER SOUTHEAST VIRGINIA AND THE WINDS WILL BE OUT OF THE NORTHWEST IN OUR COUNTY WARNING AREA. THIS POSITION IS A COMPROMISE BETWEEN THE FARTHER NORTH BUT SLOWER NAM AND THE FASTER...YET FATHER SOUTH GFS AND IS ALSO CLOSER TO ECMWF SOLUTION. DIFFERENCES IN TIMING ALSO SHOW UP IN GUIDANCE FOR TEMPERATURES WEDNESDAY NIGHT THROUGH FRIDAY. WILL STAY CLOSER TO COOLER VALUES IN THE WEST AND NORTH FOR MAXIMUM TEMPERATURES ON THURSDAY AND ACROSS THE FORECAST AREA ON FRIDAY DUE TO ALL THE CLOUDS EXPECTED IN THE MORNING. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 430 AM EDT TUESDAY... OVERALL LARGE SCALE PATTERN DOES NOT CHANGE DURING THIS TIME FRAME. UPPER TROF REMAINS OVER THE EAST. NEXT WEEK THE TROF WILL AMPLIFY AND BRING A COLD FRONT THROUGH THE REGION AROUND DAY 7...TUESDAY. AT THE SURFACE...HIGH PRESSURE BUILD IN BEHIND THE DEPARTING LOW ON FRIDAY NIGHT AND SATURDAY. INCREASING SOUTHWEST FLOW RETURNS ON MONDAY NIGHT AHEAD OF THE APPROACHING COLD FRONT. ALSO ANTICIPATING SLIGHTLY WARMER 850 MB TEMPERATURES AHEAD OF THE FRONT ON MONDAY AND TUESDAY. TEMPERATURES THROUGH THE PERIOD LOOK TO BE CLOSE TO NORMAL. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 715 PM EDT TUESDAY... WEAK FRONTAL BOUNDARY DRIFTED INTO THE REGION TODAY ALONG WITH NUMEROUS OUTFLOW BOUNDARIES FROM UPSTREAM CONVECTION. CONSIDERABLE INSTABILITY LEFT ACROSS THE REGION YET THIS EVENING. ALTHOUGH FORCING IS WEAK...WITH THE WEAK BOUNDARY IN THE AREA AND REMNANT INSTABILITY...STILL EXPECT ISOLD SHRA/TSRA TO DEVELOP THROUGH THE EVENING. OTHERWISE...EXTENSIVE HIGH LEVEL CIRRUS DEBRIS FROM WIDESPREAD CONVECTION UPSTREAM IN KY. THIS WILL LINGER ACROSS THE REGION OVERNIGHT...THEN TEND TO SHIFT SOUTH EARLY WED BEFORE MORE WIDESPREAD MID/HIGH CLOUDS SPREAD BACK INTO THE REGION FROM THE WEST LATER IN THE DAY IN ADVANCE OF A MORE WIDESPREAD SYNOPTIC RAIN EVENT PROGGED TO IMPACT THE REGION THURSDAY IN ASSOCIATION WITH AN UPPER TROUGH/BAROCLINIC ZONE/SURFACE LOW PRESSURE AREA DEVELOPING ALONG THE COAST. FOR THIS TAF VALID PERIOD...CIGS SHOULD REMAIN MOSTLY VFR...WITH THE POSSIBLE EXCEPTION OF BLF WHERE UPSLOPE WESTERLY FLOW MAY RESULT IN A PERIOD OF MVFR CIGS OVERNIGHT/EARLY WED. NOT CONVINCED THIS WILL OCCUR ANYWHERE ELSE AT THIS POINT. FOG DEVELOPMENT ALSO QUESTIONABLE BECAUSE OF EXPECTED HIGH CLOUDS. LYH HAD A TSRA TODAY WITH 0.16 RAIN...SO FOG IS A POSSIBILITY THERE...AS WELL AS LWB WHICH WILL LIKELY DECOUPLE AND SEE SOME DECREASE IN THE DENSE CIRRUS LATER TONIGHT. DURING THE DAY WED...MID/HIGH CLOUDS WILL BE ON THE INCREASE DURING THE AFTERNOON...BUT EXPECT CIGS TO REMAIN VFR THROUGH THIS TAF VALID PERIOD. WINDS W-WNW 7KTS OR LESS OVERNIGHT...WNW-WSW AFTER SUNRISE WED INCREASING TO 7-10KTS WITH LOW END GUSTS WEST OF THE BLUE RIDGE. MEDIUM TO HIGH CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION FORECAST... WIDESPREAD MVFR CIGS/VSBYS POSSIBLE THU AS A SYNOPTIC SCALE RAIN EVENT APPEARS IN THE CARDS...MORE THAN THIS AREA HAS SEEN IN OVER A MONTH. NORTHEAST WINDS WILL DEVELOP AS A RESULT OF INDUCED SFC LOW PRESSURE ALONG THE SC/NC COAST AS AN UPPER-LEVEL DISTURBANCE RIDES ALONG A STALLED FRONTAL BOUNDARY TO OUR SOUTH. BEYOND THAT...DRIER CONDITIONS RETURN FOR THE WEEKEND INTO EARLY NEXT WEEK WITH MOSTLY VFR CONDITIONS OUTSIDE OF THE TYPICAL EARLY MORNING FOG IN THE USUAL SPOTS...E.G...LWB/BCB/LYH. THE NEXT SYSTEM TO BRING MORE WIDESPREAD PRECIPITATION IN THE FORM OF SHOWERS AND THUNDERSTORMS WILL ARRIVE MONDAY NIGHT OR TUESDAY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...MBS NEAR TERM...MBS/RAB SHORT TERM...AMS LONG TERM...AMS AVIATION...MBS/RAB

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