Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 220343 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1143 PM EDT THU AUG 21 2014 .SYNOPSIS... A STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE NEAR THE GULF COAST WILL KEEP NORTHWEST FLOW IN PLACE OVER THE REGION THROUGH THE END OF THE WEEK. THIS WILL RESULT IN PERIODIC ROUNDS OF SHOWERS AND STORMS INTO SATURDAY BEFORE A COLD FRONT DROPS THROUGH FROM THE NORTH SATURDAY NIGHT. HIGH PRESSURE FOLLOWING THE FRONT SHOULD BRING DRIER AND COOLER AIR INTO THE AREA BY EARLY NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY/...
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AS OF 1115 PM EDT THURSDAY... IN BETWEEN SYSTEMS ATTM...WITH WEAK SFC HIGH OVER THE ALLEGHANYS...THOUGH HIGHER THETA-E RESULTING IN A FEW SHOWERS ACROSS WV INTO THE VA PIEDMONT. OVERALL MAINLY WATCHING UPSTREAM MCS OVER INDIANA/OHIO...AND MODELS SHARING THAT IN THE MORNING HOURS AFTER 4 AM INTO DAWN...IT WILL BE REACHING OUR SE WV COUNTIES. AT WHAT INTENSITY...WE EXPECT IT TO BE WEAKER GIVEN TIME OF DAY WITH LACK OF ANY INSTABILITY/THERMODYNAMICS. MODELS ALSO FAVOR WEAKENING THE VORT OVERNIGHT AS WELL. MAIN AXIS OF HIGHER THETA-E IS SHIFTING MORE OVER WRN WV/ERN KY SO THIS AREA OF SHOWERS AND STORM MAY DIVE MORE SSE THROUGH THE NEXT FEW HOURS. STILL NOT SEEING ENOUGH OF A THREAT OVERALL FOR FLOODING THOUGH WILL HAVE TO WATCH SOME OF OUR WV/FAR SW VA COUNTIES WHICH RECEIVED A GENEROUS 1-2 INCHES EARLIER TODAY IN SPOTS. RIGHT NOW ISOLATED FLASH FLOODING IS POSSIBLE BUT LOOKS LIKE SYSTEM WILL BE MOVING FASTER...GIVEN BROAD 8H FLOW OF 30 KNOTS. NO CHANGES TO THE FORECAST LOWS WHICH ARE EXPECTED TO BE IN THE MID 60S TO AROUND 70...FROM WEST TO EAST. KEEPING FOG IN AS WELL...MAINLY OUT EAST WHERE SOME CLEARING OUT WILL TAKE PLACE. PREVIOUS VALID DISCUSSION... NEXT WAVE SLIDES DOWN THE RESIDUAL BOUNDARY FRIDAY WITH A POSSIBLE FADING MCS ON THE DOORSTEP ACROSS THE NW EARLY ON BEFORE IT WEAKENS CROSSING THE RIDGES. HOWEVER CONFIDENCE LOW ON THIS OUTCOME GIVEN GUIDANCE UNCERTAINTY BUT DOES APPEAR BETTER COVERAGE IN ORDER ESPCLY NW EARLY AND THEN AGAIN IN THE AFTERNOON AS MAY SEE MORE WIDESPREAD CONVECTIVE BANDS FORM ALONG RESIDUAL OUTFLOW PENDING TIMING. VERY STRONG NW JET ALOFT FOR LATE AUGUST WOULD SUPPORT MORE LINEAR BOWING TYPE STORMS WITH POTENTIAL FOR SOME OF THIS COVERAGE TO CROSS THE BLUE RIDGE DESPITE THE DEEP DOWNSLOPE COMPONENT IF CAN GET ENOUGH BREAKS TO ENHANCE AFTERNOON INSTABILITY. HOWEVER MODELS REMAIN DRIER WITH MORE DEBRIS CLOUDS AROUND IN THE MORNING...AND A MIXED OUT SCENARIO IN THE AFTERNOON WHICH WOULD AGAIN LIMIT POPS TO THE NORTH/NW. THUS TRENDED IN THAT DIRECTION WITH LIKELYS EXTREME NW AND CHANCE ELSW. HIGH TEMPS REMAIN QUITE IFFY AS WARM ENOUGH ALOFT TO ZIP INTO THE 90S EAST GIVEN MORE SUN WHILE COULD GET STUCK IN THE 70S FAR WEST IF SHRA ARRIVES EARLIER AND PERSISTS. FOR NOW USED A BLEND OF THE MAV/MET MOS WITH SUPPORT FROM THE EARLIER SLIGHTLY COOLER EC 2 METER VALUES.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... AS OF 245 PM EDT THURSDAY... SYNOPTIC SCALE PATTERN CHANGING TO A HIGH AMPLITUDE TROF IN THE WEST AND RIDGE IN THE EAST. BY SUNDAY THE 591 DM CENTER OF THE 500 MB RIDGE IS OVER THE TENNESSEE VALLEY. BEST PUSH OF THE COLD FRONT AND DEEPER MOISTURE TO THE SOUTHWEST WILL BE SATURDAY NIGHT AND SUNDAY. UNTIL THEN FORECAST AREA REMAINS IN BAROCLINIC ZONE WITH THE BEST PROBABILITY OF PRECIPITATION DEPENDENT ON UPSTREAM STORMS AND TIMING OF SHORT WAVES. WILL HAVE HIGHEST PROBABILITY OF PRECIPITATION IN FOR FRIDAY NIGHT. AS HIGH PRESSURE BUILDS IN...A SURFACE LOW TRACKS DOWN THE EAST COAST. BY SATURDAY THE LOW WILL BE OVER THE CAROLINA COAST WHICH WILL HELP BRING SURFACE AND LOW LEVEL WINDS OVER THE FORECAST AREA AROUND TO THE EAST. THIS LOW MOVES WELL OFFSHORE AS THE WEDGE STRENGTHENS ON SATURDAY NIGHT AND SUNDAY. SINCE FORECAST AREA WILL BE WELL INTO THE WEDGE ON SUNDAY HAVE KEPT MAXIMUM TEMPERATURES BELOW MOST GUIDANCE. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 1130 AM EDT THURSDAY... SURFACE HIGH PRESSURE WILL BE IN A FAVORABLE LOCATION OVER NEW ENGLAND TO WEDGE WELL DOWN THE EAST SLOPES OF THE APPALACHIANS SUNDAY NIGHT AND MONDAY. SUPPORT FOR THE WEDGE WEAKENS BY TUESDAY. HIGH PRESSURE WILL REMAIN OVER THE FORECAST AREA THROUGH WEDNESDAY. WEDNESDAY NIGHT AND THURSDAY A COLD FRONT WILL APPROACH THE AREA. LARGE 500 MB RIDGE ALOFT WILL COVER MUCH OF THE LOWER MISSISSIPPI VALLEY ACROSS THE EASTERN UNITED STATES THROUGH THE PERIOD. THE DEEPEST MOISTURE SHIFTS SOUTHWEST OUT OF THE FORECAST AREA ON MONDAY AND TUESDAY. WILL HAVE THESE DAYS DRY IN THE FORECAST. THE CHANCE OF PRECIPITATION RETURNS TO THE AREA ON WEDNESDAY AND THURSDAY AHEAD OF THE FRONT. EXPECT MAXIMUM TEMPERATURES TO BE WARMEST ON WEDNESDAY AND THURSDAY WITH THE WEDGE GONE AND MORE POTENTIAL TO MIX DOWN WARM 850 MB TEMPERATURES. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... AS OF 735 PM EDT THURSDAY... STORMS WILL BE OVER DAN AT TAF TIME...AND EXITING GOING ON 0130Z. ELSEWHERE WILL BE MAINLY DRY THOUGH ISOLATED TO SCATTERED SHOWERS ARE POSSIBLE. FOG WILL BE THE MAIN CONCERN OVERNIGHT IF WE GET ENOUGH CLEARING OF THE LOW LVLS. FEEL CONFIDENT ENOUGH TO KEEP LWB LIFR PER PREVIOUS FORECAST AFTER 06Z...BUT WILL SEE MORE CLOUD STREAMING IN AHEAD OF NEXT IMPULSE THAT IS OVER NRN INDIANA THIS EVENING. THIS WILL ALLOW FOG TO ERODE AFTER 09Z...BUT WILL KEEP IFR. WILL ALSO HAVE IFR AT BLF/BCB LATER TONIGHT. MODELS SHOWING MAIN INSTABILITY AXIS AND THETA-E TO HANG OVER THE WV MTNS FRIDAY...AND STORMS SHOULD MOVE IN BY 15-17Z HERE...THEN ISSUE IS LOCATION FURTHER EAST AND COVERAGE. HAVE VCTS AT ALL SITES WITH -SHRA IN BLF/LWB...DELAYING THUNDER UNTIL AFTERNOON EAST OF WV. EXTENDED AVIATION... UPPER LEVEL DISTURBANCES WILL BE MOVING THROUGH PERIODICALLY AND INTERACTING WITH A STATIONARY FRONT OVER THE AREA FOR THE NEXT FEW DAYS...RESULTING IN PERIODS OF SHOWERS AND THUNDERSTORMS. DUE TO THE HIGH MOISTURE CONTENT OF THE AIR...EXPECT STRATUS AND FOG DURING THE OVERNIGHT PERIODS WITH AREAS OF MVFR/IFR MOST PRONOUNCED BETWEEN MIDNIGHT AND 9AM EACH DAY. MODELS ARE INDICATING THAT A DEEPER EASTERLY SORT OF WIND FLOW WILL SETUP FOR THIS UPCOMING WEEKEND. THIS SUGGESTS THAT LOW CIGS MAY PERSIST EVEN DURING THE DAYTIME PERIODS...SATURDAY AND SUNDAY...WITH WIDESPREAD MVFR CONDITIONS ACROSS THE AREA THIS WEEKEND DUE TO MOISTURE BANKING UP AGAINST THE EAST SIDE OF THE APPALACHIANS. BETTER PUNCH OF DRY AIR WITH HIGH PRESSURE BUILDING IN FROM THE NE MAY BE ENOUGH WITH MIXING/HEATING TO ALLOW FOR INCREASING VFR MONDAY INTO TUESDAY UNDER MAINLY DRY CONDITIONS. && .EQUIPMENT... THE ASOS AT LYNCHBURG (LYH) VA REMAINS PARTIALLY INOP DUE TO A BOARD FAILURE. PARTS WILL LIKELY NEED TO BE ORDERED WITH THE RETURN OF COMPLETE SERVICE UNKNOWN AT THIS TIME. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH/WP SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/PM/WP EQUIPMENT...

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