Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 310112 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 912 PM EDT SAT AUG 30 2014 .SYNOPSIS... AN UPPER LEVEL SYSTEM MOVES FROM MISSISSIPPI TO THE OHIO VALLEY THROUGH SUNDAY. THE AREA WILL REMAIN IN A TYPICAL SUMMER AIRMASS INTO TUESDAY. A FRONT ARRIVES FROM THE NORTH BY THURSDAY. && .NEAR TERM /THROUGH SUNDAY/...
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AS OF 850 PM EDT SATURDAY... WITH ISOLATED CONVECTION NOW ALL BUT GONE...PLAN TO RUN A FEW HOURS WITHOUT POP INTO THE OVERNIGHT GIVEN LOSS OF HEATING AND BEST LIFT/CONVERGENCE BACK TO THE SW OVER TN/AL. LATEST EVENING SOUNDINGS SHOW A DECENT AMOUNT OF LOW LEVEL INSTABILITY BUT CAPPED OFF ALOFT VIA THE LINGERING INVERSION/DRY AIR. APPEARS BEST MOISTURE TRAJECTORY WILL CONTINUE JUST WEST OF THE MOUNTAINS OVERNIGHT BEFORE A TRAILING TROUGH AXIS ATTEMPTS TO SHIFT EAST LATE UNDER THE PASSING WAVE ALOFT AS SEEN BY A COUPLE SHORT TERM SOLUTIONS. HOWEVER EVEN THIS LOOKS TO ARRIVE LATE WHEN THINGS ARE MORE STABLE...SO ALSO PUSHED POPS BACK WEST A BIT...WITH MAINLY CHANCE COVERAGE SE WEST VA DOWN ALONG THE I-77 CORRIDOR BY DAWN...AND ONLY SLIGHT POPS OUT TOWARD THE BLUE RIDGE. OTRW A GRADUAL INCREASE IN MID/HIGH CLOUDS EARLY ON...THEN MAINLY CLOUDY WESTERN HALF DURING THE EARLY MORNING HOURS WITH MORE PATCHY FOG POSSIBLE EAST WHERE SHOULD STAY CLEAR LONGER. NUDGED UP LOW TEMPS A FEW DEGREES IN SPOTS PER MOISTURE UNDER THE CLOUD CANOPY WHICH SUPPORTS SOME SPOTS STAYING ABOVE 70 EAST AND MOSTLY 60S WEST. SUNDAY...MODELS IN SIMILAR AGREEMENT ON TRACK OF UPPER SHORTWAVE BUT DIFFER ON EASTWARD EXTENT AND AMOUNT OF PRECIP. THE 12Z NAM OVERALL LOOKED TO BULLSEYEISH WITH FINGERS OF HIGHER QPF ACROSS THE NC MTNS INTO SW VA...SO LEANED THE FORECAST TOWARD THE 12Z ECMWF/GFS...WHICH FOR THE MOST PART TAKE THE HIGHER POPS ACROSS THE NW NC/SW VA/SRN WV AREA INTO THE SHENANDOAH VALLEY TOMORROW...WITH LESS THREAT OF SHOWERS AND STORMS EAST OF THE DAN/LYH CORRIDOR. TEMPS WILL BE TEMPERED BY THE CLOUD COVER SO LOOKING AT HUMID CONDITIONS WITH HIGHS RANGING FROM THE UPPER 70S-LOWER 80S MOUNTAINS...TO MID TO UPPER 80S EAST.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 315 PM EDT SATURDAY... SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL PERSIST THROUGH SUNDAY NIGHT INTO MONDAY MORNING...WITH GREATEST RAIN CHANCES FOUND WEST OF INTERSTATE 81...AS AN UPPER LEVEL DISTURBANCE SHIFTS ACROSS THE GREAT LAKES FROM THE OHIO RIVER VALLEY. WITH A VERY MOIST ATMOSPHERE IN PLACE...MAY SEE A FEW AREAS OF EXCESSIVE RAINFALL... BUT BELIEVE THE FLOODING THREAT WILL BE LOW DUE TO A WEEK OF DRY CONDITIONS. MAY SEE A FEW SHOWERS REDEVELOP MONDAY AFTERNOON AS WE APPROACH MAXIMUM HEATING...BUT BELIEVE THIS ACTIVITY WILL BE MORE DISORGANIZED DUE TO DRIER CONDITIONS AS HIGH PRESSURE MOVES IN FROM THE SOUTH...AS WELL AS A LACK OF UPPER LEVEL SUPPORT. RAINFALL WILL DIMINISH QUICKLY AS THE SUN SETS AND SHOULD SEE DRY...ALBEIT WARM AND MUGGY...CONDITIONS PERSIST THROUGH MONDAY NIGHT. RAIN CHANCES WILL INCREASE AGAIN ON TUESDAY AS ANOTHER LOW PRESSURE SYSTEM MOVING ACROSS EASTERN CANADA WILL DRAG A COLD FRONT SOUTH OF THE GREAT LAKES. BETTER CHANCES FOR RAIN WILL BE FOUND ACROSS THE MOUNTAINS...WHERE STRONGER UPPER LEVEL SUPPORT WILL BE LOCATED. BELIEVE MODELS ARE TOO AGGRESSIVE IN PUSHING THE FRONT INTO NORTH CAROLINA PER THE 30/12Z RUNS...AND EXPECT THE COLD FRONT WILL STALL FURTHER NORTH DUE TO THE UPPER LEVEL RIDGING IN PLACE ACROSS THE SOUTHEAST STATES...PERHAPS SOMEWHERE BETWEEN THE INTERSTATE 64 AND HIGHWAY 460 CORRIDORS DURING TUESDAY NIGHT. TEMPERATURES WILL REMAIN SLIGHTLY ABOVE NORMAL FOR THE EARLY HALF OF THE WEEK...WITH HIGHS RANGING FROM THE UPPER 70S/LOW 80S ACROSS THE MOUNTAINS...TO THE LOW 90S ACROSS THE SOUTHSIDE. LOWS WILL FALL INTO THE MID 60S TO LOW 70S. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 330 PM SATURDAY... UPPER LEVEL RIDGING WILL SHIFT NORTHWARD FROM THE SOUTHEAST STATES OVER THE MID ATLANTIC DURING THE SECOND HALF OF THE WEEK...RESULTING IN BOTH WARMER TEMPERATURES AND WEAKER WINDS ALOFT. THIS WILL MAKE FOR MORE STABLE CONDITIONS THAT WILL KEEP SHOWER AND THUNDERSTORM ACTIVITY DISORGANIZED THROUGH THE PERIOD. ANY RAINFALL WHICH DEVELOPS WILL BE DRIVEN MAINLY BY DAYTIME HEATING...WHICH WILL ALLOW THIS ACTIVITY TO FIZZLE AFTER SUNSET. EXPECT WIDELY SCATTERED SHOWERS AND PERHAPS A THUNDERSTORM OR TWO TO DEVELOP WEDNESDAY AFTERNOON ALONG THE STALLED FRONTAL BOUNDARY... WHEREVER IT IS LOCATED. HIGH PRESSURE PASSING ACROSS THE GREAT LAKES SHOULD KEEP THE NORTHERN HALF OF OUR AREA DRY. HIGH PRESSURE WILL PASS OFF THE NEW ENGLAND COAST ON THURSDAY... RESULTING IN A WEAK WEDGING PATTERN WITH EASTERLY FLOW OFF THE ATLANTIC. THIS WILL LIKELY BE THE DRIEST DAY OF THE PERIOD. WINDS WILL SHIFT SOUTHWESTERLY AGAIN ON FRIDAY AS ANOTHER COLD FRONT SINKS SOUTH FROM THE GREAT LAKES. STRONGER FLOW OFF THE ATLANTIC WILL RESULT IN INCREASED MOISTURE...AND WILL EXPECT SPOTTY SHOWER AND THUNDERSTORM ACTIVITY DURING THE AFTERNOON AND EVENING. EXPECT TEMPERATURES TO REMAIN SLIGHTLY ABOVE NORMAL FOR THE PERIOD. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... AS OF 650 PM EDT SATURDAY... OTHER THAN FOR VERY ISOLATED SHRA/TSRA ALONG THE BLUE RIDGE...MOST OF THE AREA REMAINS VOID OF CONVECTION THIS EVENING WITH WIDESPREAD VFR IN PLACE UNDER A SCATTERED TO BROKEN CU FIELD. EXPECT THIS SCENARIO TO PREVAIL THROUGH THE EVENING WITH PERHAPS A FEW MORE POP UP SHRA/TSRA UNTIL THE BOUNDARY LAYER COOLS AFTER SUNSET. OTRW MAIN CONCERNS OVERNIGHT WILL BE WITH BANDS OF SHRA HEADING NORTH FROM THE SE STATES AHEAD OF SHORTWAVE ENERGY EJECTING BY TO THE WEST LATE TONIGHT...AND DEGREE OF FOG COVERAGE. APPEARS SOME OF THE CONVECTION TO THE SW COULD ARRIVE OVER THE FAR WEST WELL AFTER MIDNIGHT AND SLIDE EAST TOWARD THE BLUE RIDGE EARLY SUNDAY BEFORE FADING. THUS INCLUDED A VCSH MENTION OVER THE SE WEST VA LOCATIONS AROUND DAWN AND EXTENDED EAST TO KBCB EARLY SUNDAY. EXPECT SOME FOG AGAIN IN THE VALLEYS GIVEN OVERALL LACK OF CLOUDS EARLY WHILE MODELS INDICATE POTENTIAL FOR LOW CIGS TO REDEVELOP OVER THE SOUTH/SE LATE AS MOISTURE INCREASES. APPEARS BEST SHOT AT MVFR IN FOG OUT EAST AT KLYH/KDAN WITH ONLY SPOTTY/BRIEF NATURE FOG ELSW WITH CLOUDS ARRIVING LATE. RESIDUAL SHRA BAND LIKELY TO DISSIPATE HEADING EAST SUNDAY MORNING AS THE MAIN AREA OF LIFT TAKES SHAPE OFF TO THE WEST WITH THE MAIN SHORTWAVE AXIS THAT WILL BE PASSING TO THE NW SUNDAY EVENING. THIS COULD ALLOW ANY EARLY MVFR CIGS TO FADE INTO MORE OF A SCATTERED/BROKEN VFR CU FIELD WITH HEATING AT ALL SITES DURING THE AFTERNOON BEFORE INSTABILITY AIDED BY WESTERN OROGRAPHICS HELPS POP A FEW SHRA/TSRA LATER SUNDAY. DONT SEE MUCH OF THIS GETTING TOO FAR EAST OF THE BLUE RIDGE SO ONLY INCLUDING A PREVAILING LOWER VSBY IN SHRA AT KBLF/KLWB WITH A VCTS MENTION. ELSW THINK KBCB/KROA WILL BE ON THE EDGE OF THE WESTERN CONVECTIVE SHIELD SO ADDED VCSH AT KBCB AND LEFT KROA AND POINTS EAST DRY FOR NOW. EXTENDED DISCUSSION... SHOWERS AND STORMS LIKELY TO PUSH EAST ACROSS MUCH OF THE AREA...AT LEAST ON A SCATTERED BASIS...SUNDAY EVENING WITH PERIODS OF SUB-VFR POSSIBLE. THIS WILL BE FOLLOWED BY MORE WIDESPREAD FOG SUNDAY NIGHT INTO EARLY MONDAY WITH POCKETS OF MVFR/IFR IN FOG/STRATUS LIKELY. IMPULSE PASSES BY MONDAY LEAVING THE REGION IN BETWEEN THIS EXITING SYSTEM AND THE NEXT UPSTREAM COLD FRONT. THIS SHOULD ALLOW FOR MORE IN THE WAY OF WIDESPREAD VFR ON MONDAY AFTER EARLY FOG FADES WITH ONLY ISOLATED CONVECTION LIKELY DURING THE AFTERNOON INCLUDING SPOTTY MVFR. ANOTHER COLD FRONT IS EXPECTED TO PRODUCE SIMILAR CONDITIONS AS IT APPROACHES FROM THE NW TUESDAY...THEN PERHAPS BETTER COVERAGE OF SHRA/TSRA WEDNESDAY WITH THE FRONT PASSING...AND ACROSS THE SOUTH THURSDAY WHERE THE BOUNDARY LOOKS TO STALL. HOWEVER TIMING AND SOUTHWARD EXTENT OF THE BOUNDARY QUITE LOW CONFIDENCE AT THIS POINT. THUS APPEARS MAINLY VFR FOR NOW TUE-THU OUTSIDE OF AFTERNOON/EVENING CONVECTION AND TYPICAL EARLY MORNING FOG IN THE VALLEYS AND WHERE EARLIER HEAVY RAIN OCCURRED. && .EQUIPMENT... AS OF 730 AM EDT FRIDAY ... THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...JH/WP SHORT TERM...NF LONG TERM...NF AVIATION...AMS/JH/WP EQUIPMENT...AMS

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