Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 031142 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 742 AM EDT FRI JUL 3 2015 .SYNOPSIS... A LOW PRESSURE SYSTEM WILL MOVE OUT OF THE OHIO VALLEY AND INTO THE MIDDLE ATLANTIC REGION. THIS WILL BRING SHOWERS AND THUNDERSTORMS TO THE AREA...ALONG WITH CONTINUED COOL TEMPERATURES...AS WE CLOSE OUT THE WORKWEEK. UNFORTUNATELY OUR WEATHER WILL REMAIN UNSETTLED...WITH A SERIES OF UPPER LEVEL DISTURBANCES BRINGING A CHANCE FOR SHOWERS AND THUNDERSTORMS THE REGION THROUGHOUT THE HOLIDAY WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM EDT FRIDAY... SHORT WAVE ENERGY ENTERING THE MEAN UPPER TROF OVER THE EASTERN US WILL DRIVE A WAVE OF LOW PRESSURE AT THE SURFACE FROM THE OHIO VALLEY TO THE MID ATLANTIC REGION. THIS WILL TAKE THE FRONTAL BOUNDARY THAT PUSHED SOUTH OF OUR AREA YESTERDAY AND DRAG IT BACK NORTHWARD AS A WARM FRONT WITH WEAK HIGH PRESSURE WEDGING DOWN THE EAST SIDE OF THE APPALACHIANS. EARLY MORNING SATELLITE AND RADAR LOOPS SHOW THAT THINGS ARE BEGINNING TO COME TOGETHER AS THE VIGOROUS CONVECTION OVER TENNESSEE IS BEGINNING TO MOVE MORE TOWARD THE EAST/NORTHEAST...WHICH IS HEADING IN OUR DIRECTION. THIS SYSTEM HAS A LOT GOING FOR IT WITH GOOD DYNAMIC ENERGY AND A VERY MOIST AIRMASS IN PLACE. HODOGRAPHS ARE SMALL BUT SHOW A SIGNIFICANT AMOUNT OF SHEAR AS WOULD BE EXPECTED IN THE VICINITY OF A FRONTAL BOUNDARY. THE MISSING INGREDIENT FOR SEVERE WEATHER TODAY IS INSTABILITY. ABUNDANT CLOUD COVER COMBINED WITH THE SOMEWHAT EARLY ONSET TIME WILL LIMIT DAYTIME HEATING AND MODEL SOUNDINGS IN BUFKIT ARE SHOWING A LONG AND SKINNY CAPE PRESENTATION WHICH DOES NOT FAVOR VIGOROUS UPDRAFTS. BASED ON THESE FACTORS...CURRENTLY ANTICIPATE A SEASONABLE WITH UPPER 60S EAST TO LOWER 60S WEST.EALTHY AREA OF SHOWERS WITH EMBEDDED THUNDER WILL MOVE ACROSS THE AREA FROM WEST TO EAST TODAY WITH ACTIVITY MOVING OUT AND WINDING DOWN THIS EVENING/EARLY TONIGHT. THIS SITUATION WILL BE MONITORED VERY CLOSELY SINCE IF THE CLOUD COVER IS LESS THAN CURRENTLY ANTICIPATED AND WE CAN GENERATE GREATER AMOUNTS OF INSTABILITY...ESPECIALLY ACROSS THE SOUTHERN AND EASTERN PORTIONS OF THE AREA...THE SEVERE THREAT WILL INCREASE. WITH PRECIPITABLE WATER VALUES RUNNING WELL ABOVE NORMAL HEAVY DOWNPOURS CAN BE EXPECTED...BUT THE LACK OF WIDESPREAD SIGNIFICANT RAINFALL ON THURSDAY HAS EASED CONCERN FOR FLOODING A BIT SO WILL NOT BE ISSUING A FLOOD WATCH WITH THIS PACKAGE. WILL CONTINUE TO HIGHLIGHT THE POTENTIAL FOR HEAVY RAIN AND POSSIBLE HYDRO ISSUES IN THE HWO. AS THE LOW MOVES OFF TO OUR NORTHEAST TONIGHT THE FRONTAL BOUNDARY WILL SWING BACK THROUGH THE REGION AS A COLD FRONT. THIS WILL YIELD SOME LINGERING SHOWERS WEST OF THE BLUE RIDGE WITH SOME IMPROVEMENT TO THE EAST HIGH TEMPERATURES TODAY WILL CONTINUE ON THE COOL SIDE WITH READINGS IN THE LOWER 80S EAST OF THE RIDGE TO THE LOWER 70S WEST...AND LOWS TONIGHT RANGE FROM THE UPPER 60S EAST TO LOWER 60S WEST. && .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... AS OF 415 AM EDT FRIDAY... THE BROAD UPPER TROUGH PLAUGING THE EASTERN U.S. WILL UNDERGO SOME SUBTLE MODIFICATIONS DURING THIS PERIOD. SAT-SUN...THE UPPER TROUGH WILL TAKE ON A POSITIVE TILT AS A SHORT WAVE RIDGE BUILDS INTO THE GREAT LAKES/PA REGION. MEANWHILE...THE SOUTHERN END BECOMES CUTOFF ACROSS THE CAROLINAS AND LINGERS ACROSS THAT REGION SUN...THEN GRADUALLY DRIFTS BACK NORTHWARD INTO EASTERN VA MON AND NORTHERN VA TUE. THUS...THE AREA REMAINS UNSETTLED AND WET...BUT WITH A GRADUAL SHIFT OF THE BETTER COVERAGE OF SHOWERS AND THUNDERSTORMS TOWARD THE EASTERN PART OF THE CWA WITH TIME. FOR SATURDAY...YET AGAIN...POTENTIAL FOR WIDESPREAD SHOWERS AND EMBEDDED THUNDERSTORMS TO START OFF THE DAY...JUST AS HAS BEEN THE CASE THE PAST TWO DAYS. HOWEVER...CONFIDENCE IN THIS IS LOW AT THIS POINT AS IT WILL LARGELY BE BASED ON UPSTREAM CONVECTIVE COMPLEXES...TRACK...AND INTENSITY. HOWEVER...FEEL THAT CONFIDENCE IN ONGOING PRECIPITATION AT 12Z IS SLIGHTLY GREATER THAN THE PAST TWO DAYS AS THE UPPER TROUGH SHIFTS EAST MOVING THE CURRENT CORRIDOR OF PRECIPITATION ACROSS THE TN VALLEY EASTWARD INTO OUR REGION. THE EXTENT OF CLOUDS AND PRECIPITATION IN THE MORNING WILL DETERMINE THE DEGREE OF INSTABILITY AND HENCE CONVECTIVE COVERAGE LATER IN THE DAY. UPPER FLOW TENDS TO BECOME MORE SOUTHWEST INSTEAD OF NORTHWEST DURING THIS PERIOD GIVEN THE TRANSITION OF THE WEAK UPPER LOW TO THE SOUTH OF THE REGION. THIS SHOULD BE ENOUGH TO SUPPORT HIGH CHANCE TO LIKELY POPS INTO THE AFTERNOON/EVENING. SPC CURRENTLY ONLY HAS GENERAL THUNDER ACROSS THE REGION GIVEN THE LACK OF INSTABILITY. WITH FAIRLY WET ANTECEDENT CONDITIONS...THE MAIN CONCERN WILL BE HEAVY RAINFALL AND LOCALIZED FLOODING. HOWEVER...IT APPEARS UNLIKELY THAT FFG WILL BE EXCEEDED AS RAINFALL AMOUNTS WOULD NEED TO EXCEED 2-2.5 INCHES IN 1-3 HRS MOST LOCATIONS FOR THIS TO OCCUR. PROJECTED RAINFALL FOR THE THREE DAY PERIOD TODAY THROUGH SUNDAY IS MOSTLY 1.5 TO 2.5 INCHES. FOR SUNDAY...THE WEAK UPPER LOW DRIFTS BACK NORTH INTO THE CWA. WIDESPREAD SHOWERS AND THUNDERSTORMS APPEAR LIKELY...BUT THE EXTENSIVE CLOUD COVER WILL AGAIN LIMIT INSTABILITY. ONCE AGAIN...LOCALIZED HEAVY RAINFALL WILL BE THE MAIN CONCERN...BUT GIVEN THAT THE HEAVIEST RAINFALL SHOULD REMAIN MOSTLY EAST OF THE MOUNTAINS...THIS FURTHER REDUCES CONCERNS OF FLOODING. HOWEVER...THE PATTERN DOES ONCE AGAIN SUPPORT LIKELY POPS ACROSS MUCH OF THE CWA...ESPECIALLY EASTERN SECTIONS. MONDAY PROMISES TO BE YET ANOTHER WET DAY AS THE REMNANT UPPER LOW DRIFTS INTO NORTHERN VA. ONCE AGAIN...THE BEST COVERAGE OF PRECIPITATION SHOULD BE ACROSS THE EASTERN SECTIONS...BUT DIFFERENTIAL HEATING ACROSS THE MOUNTAINS SHOULD RESULT IN AN UPTICK OF AFTERNOON CONVECTION THERE AND FURTHER NORTH COMPARED TO SUN. AGAIN...HIGH CHANCE TO LIKELY POPS APPEAR IN ORDER. INSTABILITY ONCE AGAIN APPEARS MARGINAL AND THE MAIN CONCERN WILL REMAIN THAT OF LOCALIZED HEAVY RAINFALL. MAX TEMPS SHOULD REMAIN WELL BELOW NORMAL THROUGH THE PERIOD THANKS TO CLOUD COVER AND PRECIPITATION...WITH HIGHS MOSTLY IN THE 70S...TO LOWER 80S EAST IF A FEW BREAKS IN THE OVC CAN OCCUR. ON THE OTHER HAND...LOW TEMPERATURES WILL REMAIN ABOVE NORMAL THANKS TO HIGH PWATS/DEWPOINTS AND CONSIDERABLE CLOUD COVER. && .LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 430 AM EDT FRIDAY... BY TUESDAY...THERE IS FAIRLY GOOD AGREEMENT AMONG THE MODELS THAT THE CUT OFF UPPER LOW LINGERING ACROSS THE REGION WILL SPLIT IN TWO...WITH THE PART ACROSS NORTHERN VA LIFTING NORTHEAST TOWARD NY/NEW ENGLAND...AS THE PARENT UPPER LOW SINKS SOUTHWARD TOWARD THE FL PANHANDLE/SOUTH GA. MEANWHILE...A SHORT WAVE AND ASSOCIATED FRONT WILL APPROACH FROM THE NORTHWEST BY TUESDAY...THEN DRIFT INTO THE REGION AND STALL WED-THU. AT THIS POINT...TUE SHOULD BE THE DAY WITH THE LOWEST POPS OVERALL...AND LIKELY LOWER THAN ANY PRIOR DAYS OR SUCCEEDING DAYS. ONCE THE FRONT DRIFTS INTO THE REGION WED AND STALLS...WAVES OF LOW PRESSURE WILL RIDE ALONG THE FRONT AND KEEP GOOD CHANCES OF SHOWERS/THUNDERSTORMS ACROSS THE REGION. HOWEVER...COMPARED TO THE CURRENT WEEK WITH NORTHWEST FLOW...UPPER FLOW WILL BE MORE WEST-SOUTHWEST AS BROAD UPPER RIDGING IS NOTED ACROSS THE SOUTHERN STATES. PRECIPITATION OVERALL SHOULD BE SLIGHTLY MORE DIURNAL IN NATURE...I.E...LESS NOCTURNAL...AS A RESULT AND TEMPERATURES WILL CERTAINLY BE TRENDING WARMER...BUT REMAIN MOSTLY 70S MOUNTAINS AND 80S PIEDMONT AS 850MB TEMPS TOP OUT IN THE +16C TO +18C RANGE. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 730 AM EDT FRIDAY... POOR AVIATION CONDITIONS EXPECTED THROUGH THE TAF VALID PERIOD AS BROAD UPPER TROUGH AND EMBEDDED DISTURBANCES CONTINUE TO TRACK ACROSS THE REGION. CONFIDENCE IS LOW IN TIMING OF CONVECTIVE COMPLEXES AND DEGREE OF INSTABILITY FOR HEAVIER AFTERNOON/EVENING CONVECTION GIVEN WIDESPREAD MORNING SHOWERS. AREA OF SHOWERS AND EVEN A FEW THUNDERSTORMS AT THIS HOUR SPREADING TO THE WESTERN PART OF THE REGION ALREADY. MODELS SHOW THIS TRACKING FROM SOUTHWEST TO NORTHEAST THROUGH THE MORNING...THEN ANOTHER AREA OF CONVECTION...POSSIBLY STRONGER...ARRIVING DURING THE AFTERNOON/EVENING...BEFORE SHIFTING TO THE EAST OF THE CWA BY SATURDAY MORNING. HAVE ADVERTISED WIDESPREAD MVFR CIGS AND VSBYS EAST OF THE BLUE RIDGE IN SHRA AND OCCASIONAL TSRA THROUGH THE EVENING...WITH MVFR-IFR CIGS/VSBYS WEST OF THE BLUE RIDGE THROUGH THE EVENING. OVERNIGHT...HEAVIER PRECIPITATION SHOULD SHIFT EAST...BUT LINGERING SHOWERS WILL REMAIN. IN ADDITION...CONDITIONS APPEAR FAVORABLE FOR WIDESPREAD IFR-LIFR CIGS/VSBYS IN FOG AND LOW CLOUDS...ESPECIALLY BLF/LWB/BCB. WINDS GENERALLY NE-SE 3-7KTS THROUGH THE DAY IN ADVANCE OF A WEAK AREA OF SFC LOW PRESSURE TRACKING ALONG THE QUASI-STATIONARY FRONT DRAPED ACROSS THE REGION. WINDS SHOULD BECOME SSW-SW 3-6KTS BEHIND THE HEAVIER SHRA/TSRA ACTIVITY THIS EVENING. LOW TO MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID PERIOD. LOW TO MEDIUM CONFIDENCE IN THUNDERSTORM POTENTIAL THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN WIND DIRECTION/MEDIUM TO HIGH CONFIDENCE IN WIND SPEED THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... POOR AVIATION CONDITIONS LIKELY TO CONTINUE INTO EARLY NEXT WEEK...BUT WINDOWS OF OPPORTUNITY FOR VFR CONDITIONS INCREASE AS WE MOVE INTO MON/TUE. UPPER LOW/TROUGH WILL LINGER WEST OF THE VA/NC COASTAL PLAIN INTO THE SOUTHEAST STATES THROUGH THE WEEKEND...THEN BEGIN TO DRIFT INTO NORTHERN VA BY MON. MEANWHILE...A COLD FRONT WILL APPROACH FROM THE OH VALLEY BY WED. THIS LEAVES A VERY UNSETTLED/WET PATTERN ACROSS THE REGION THROUGH THE PERIOD. EXPECT WIDESPREAD LATE NIGHT/EARLY MORNING LOW CLOUDS/FOG WITH IFR-LIFR CIGS/VSBYS. OVERALL...CONDITIONS SHOULD IMPROVE TO MVFR-VFR OUTSIDE SHRA/TSRA ACTIVITY DURING THE AFTERNOONS. AT THIS POINT...TUESDAY APPEARS TO OFFER THE BEST OPPORTUNITY FOR MORE WIDESPREAD VFR CONDITIONS.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...RAB LONG TERM...RAB/RCS AVIATION...MBS/NF/RAB

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