Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230824 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 424 AM EDT SAT AUG 23 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD ALONG THE NORTHERN MID-ATLANTIC COAST THROUGH THE WEEKEND PUSHING A BACKDOOR FRONT THROUGH THE REGION FROM THE EAST. SHOWERS AND A FEW THUNDERSTORMS WILL ACCOMPANY THE FRONT AGAIN TODAY WITH WARM...HUMID CONDITIONS CONTINUING. FOR SUNDAY INTO EARLY NEXT WEEK...THE FRONT WILL CONTINUE TO PUSH WEST INTO THE TENNESSEE VALLEY ALLOWING DRIER...COOLER AIR TO FILTER INTO THE REGION FROM THE EAST. THIS AIR MASS WILL REMAIN IN PLACE THROUGH THE MID PART OF NEXT WEEK RESULTING IN INCREASED SUNSHINE...LESS HUMIDITY...COOL NIGHTS AND MILD TO SEASONABLY WARM DAYS. && .NEAR TERM /THROUGH SUNDAY/... THE BAROCLINIC ZONE...PARKED OVER THE REGION FOR THE PAST SEVERAL DAYS...WILL BEGIN TO DRIFT WEST TODAY AS CONFLUENT FLOW ALOFT DEVELOPS ACROSS THE NORTHEAST U.S. THINKS TO A STRONG MID- LEVEL RIDGE BUILDING NORTHEASTWARD FROM THE MS VALLEY AND A BROAD AREA OF LOW PRESSURE ACROSS THE NORTHERN. THIS WILL FINALLY PUSH THE LONG STANDING BAROCLINIC ZONE WEST INTO THE TN VALLEY SUN-MON. IN SO DOING...MORE STABLE MARITIME AIR WILL SPREAD INTO THE REGION FROM THE EAST...BEGINNING LATE TODAY...THEN SPREADING WEST TOWARD THE WESTERN BORDER OF THE CWA BY SUN. FOR TODAY...EXPECT MORE SHOWERS AND THUNDERSTORMS ACROSS THE REGION. ACTIVITY HAS LINGERED IN VARIOUS AREAS OVERNIGHT...MOSTLY JUST NORTH AND SOUTHWEST OF THE CWA...WHERE LOCALLY HEAVY RAINFALL AND FLASH FLOODING HAS BEEN REPORTED. THIS WILL REMAIN A POSSIBILITY THROUGHOUT THE DAY. THE FOCUS FOR HEAVIER RAIN WILL FOCUS MAINLY WEST OF THE BLUE RIDGE BY AFTERNOON AS THE FRONT DRIFTS WEST. WITH PWATS STILL IN THE 1.5-1.9 INCH RANGE FROM NE- SW...LOCALLY HEAVY RAIN CAN STILL BE EXPECTED. HOWEVER...NONE OF THE SHORT RANGE OR LONG RANGE MODELS INDICATE ANY EXCESSIVE RAINFALL BY ANY MEANS OVERALL...WITH ONLY MODEST AMOUNTS ALL LESS THAN 1 INCH FOR THE 24HR PERIOD ENDING 12Z SUN. EARLIER FFA WAS CANCELLED AND FEEL ANY FLOODING ISSUES TODAY...AGAIN MAINLY WEST OF THE BLUE RIDGE...CAN BE HANDLED WITH LOCAL FLOOD ADVISORIES OR IN THE WORST CASE SCENARIOS FLASH FLOOD WARNINGS. WITH RESPECT TO THUNDERSTORMS...HAVE INDICATED AT LEAST ISOLD TSRA ALL AREAS TODAY...BUT THE MOST LIKELY AREA WILL BE WEST OF THE BLUE RIDGE...AND ESPECIALLY FAR SW VA/NW NC/SE WV WEST OF THE FRONTAL BOUNDARY WHERE AFTERNOON CAPES EXCEED 1000 J/KG. SPC DOES NOT HAVE ANY AREA INDICATED FOR SEVERE...HOWEVER...AN ISOLD WET DOWNBURST CANNOT BE RULED OUT...ESPECIALLY NEAR THE FRONTAL BOUNDARY. AGAIN...THE MAIN CONCERN WOULD BE LOCALLY HEAVY RAIN WEST OF THE BLUE RIDGE AND ESPECIALLY AREAS WEST OF I-77. OVERNIGHT INTO EARLY SUN...WOULD EXPECT INCREASING LIKELIHOOD OF -DZ DEVELOPING EAST OF THE ALLEGHANY FRONT AS THE MARITIME LAYER DEEPENS. WITH RESPECT TO TEMPERATURES TODAY...A TRANSITION IN THE AIR MASS FROM WARM/HUMID/SUMMERLIKE TO ATLANTIC MARITIME WILL BE TAKING PLACE EAST OF THE BLUE RIDGE...WITH WESTERN AREAS REMAINING VERY WARM AND HUMID UNDER THE INFLUENCE OF THE UPPER RIDGE. USED A MODEL BLEND FOR TODAY...BUT AFTER TODAY THE GFS MOS JUST LOOKS WAY TO WARM FOR THE SYNOPTIC SITUATION DEVELOPING. MIN TEMPS SUN MORNING SHOULD REMAIN QUITE MILD WITH DEWPOINTS STILL 65-70 IN MANY AREAS. ECMWF MOS SEEMS TO HAVE THE BEST HANDLE ON TEMPS THROUGH SUN. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 300 AM EDT SATURDAY... THIS PERIOD OF THE FORECAST WILL OFFER A TREND TOWARDS DRIER CONDITIONS. A BACKDOOR COLD FRONT WILL BE WELL TO THE WEST AND SOUTH OF THE AREA BY SUNDAY EVENING. BEHIND IT...HIGH PRESSURE WILL START TO NOSE SOUTH ALONG THE SPINE OF THE APPALACHIANS. THE FORECAST WILL REFLECT A TYPICAL COLD AIR DAMMING WEDGE PATTERN WITH MOST AREAS OF THE FORECAST AREA SOCKED IN WITH CLOUDS...PATCHY DRIZZLE...AND SLIGHTLY BETTER ORGANIZED LIGHT RAIN GIVEN THE EASTERLY UPSLOPE COMPONENT OF RESIDUAL LOW LEVEL MOISTURE. MODEL GUIDANCE WANTS TO BRING DRIER AIR INTO THE REGION AS EARLY AS MID-DAY SUNDAY. WHILE IT IS STILL AUGUST...GUIDANCE TENDS TO BE A BIT TOO PROMPT IN CLEARING OUT THE IMPACTS OF THE WEDGE. AS SUCH...THE FORECAST WILL CONTINUE TO HOLD THE WEDGE FAST THROUGH THE DAY SUNDAY...ALL WHILE MAKING ADJUSTMENTS ALONG THE BORDERS WITH OTHER OFFICE TO BETTER BLEND WITH THEIR DRIER AND MILDER FORECASTS. SUNDAY NIGHT INTO MONDAY...WE ARE EXPECTING THE WEDGE AND ASSOCIATED CLOUDS AND DRIZZLE TO GRADUALLY ERODE...BUT LINGER THE LONGEST ALONG THE CREST OF THE BLUE RIDGE FROM ROUGHLY FLOYD VA SOUTHWEST INTO THE NORTHERN MOUNTAINS OF NORTH CAROLINA. BY MONDAY NIGHT...THE FORECAST WILL REFLECT DRY HIGH PRESSURE WINNING OUT ACROSS THE ENTIRE REGION WITH LITTLE IN THE WAY OF CLOUD COVER REMAINING. THIS REGIME IS EXPECTED TO CONTINUE THROUGH AT LEAST TUESDAY NIGHT. HIGH TEMPERATURES WILL GRADUALLY MODERATE AS MORE AND MORE OF THE REGION EXPERIENCES SUNNY SKIES OVER CLOUDY ONES. NIGHTTIME LOWS THOUGH WILL TREND LOWER AS LESS CLOUD COVER...LOWER DEW POINTS...AND LIGHT WINDS YIELD COOLER TEMPERATURES. BY MONDAY AND TUESDAY NIGHTS...LOWS IN THE MID TO UPPER 50S WILL BE COMMON ACROSS THE MOUNTAINS WITH READINGS AROUND 60 ACROSS THE PIEDMONT. HIGH TEMPERATURES BY TUESDAY WILL MODERATE INTO THE UPPER 70S TO AROUND 80 ACROSS MUCH OF THE AREA. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 1145 AM EDT FRIDAY... DEEP UPPER TROF CROSSING THROUGH THE CENTRAL UNITED STATES COMPLETELY FLATTENS THE SOUTHEAST RIDGE ON WEDNESDAY AND THURSDAY. SPREAD OF SOLUTIONS ON MODELS BECOMES QUITE LARGE BY WEDNESDAY. WPC WAS LEANING TOWARD THE LESS AMPLIFIED...MORE PROGRESSIVE ECMWF. THE SURFACE HIGH THAT WEDGES DOWN THE APPALACHIANS STARTS OUT OVER NEW ENGLAND...THEN BY WEDNESDAY THE PARENT HIGH MOVES OFFSHORE. BY THAT TIME THE AMOUNT OF EASTERLY FLOW AND RIDGING WILL BE INFLUENCED BY WHATEVER TROPICAL SYSTEM WILL BE FATHER EAST IN THE ATLANTIC. A COLD FRONT OVER THE GREAT LAKES ON WEDNESDAY WILL APPROACH THE FORECAST AREA LATE ON THURSDAY. MODELS SUGGEST NOT A LOT OF SOUTHWARD PUSH OF THIS FRONT. BOUNDARY MAY STILL BE IN THE AREA ON FRIDAY. AS THE SURFACE WEDGE BREAK DOWN AND THE FRONT APPROACHES...850 MB TEMPERATURES WILL RISE. FORECAST AREA WILL BE DRY AT MID AND UPPER LEVELS MONDAY NIGHT THROUGH WEDNESDAY NIGHT. THEN BY THURSDAY DEEPER MOISTURE COMES BACK INTO THE AREA ALONG THE FRONT. ECMWF EVEN SHOWED DRYING WELL BELOW 850 MB ON TUESDAY. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... AS OF 145 AM EDT SATURDAY... FAIRLY POOR AVIATION CONDITIONS EXPECTED THROUGH THE TAF VALID PERIOD AS BAROCLINIC ZONE...ORIENTED FROM NW-SE...SLOWLY DRIFTS WESTWARD THROUGH THE WEEKEND AS HIGH PRESSURE MOVES TOWARD THE NORTHERN MID-ATLANTIC REGION SETTING UP A FAIRLY CLASSIC WEDGE PATTERN UNDERNEATH A BUILDING UPPER RIDGE. THIS PATTERN WILL CONTINUE TO RESULT IN VARIABLE CLOUD CONDITIONS...ALONG WITH SCT SHRA AND SOME TSRA WESTERN AREAS DURING THE AFTERNOON. UNTIL THE BAROCLINIC ZONE DRIFTS FURTHER WEST...CANNOT RULE OUT -SHRA FROM TIME TO TIME...SO HAVE RETAINED MENTION OF VCSH MOST HOURS AT MOST SITES. CIGS WILL VARY FROM VFR AT TIMES...MAINLY LATE MORNING THROUGH LATE AFTERNOON...TO MOSTLY MVFR AT NIGHT...LOCALLY IFR- LIFR IN FOG/LOW CLOUDS. VSBYS MOSTLY VFR OUTSIDE SHRA/TSRA AREAS AND LATE NIGHT/EARLY MORNING FOG. THE USUAL DENSE RADIATION FOG AT LWB/BCB...NOT A DEFINITE OCCURRENCE BECAUSE OF THICK MID CLOUDS...BUT THERE IS POTENTIAL GIVEN THE HIGH PWAT AND SATURATED GROUND FROM RECENT HEAVY AND REPEATED HEAVY RAINFALL. AS THE BACKDOOR FRONT/WEDGE EVOLVES THROUGH THE DAYTIME...EXPECT WINDS TO TRANSITION TO THE NE-ENE EAST OF THE BLUE RIDGE...WITH WNW-NW WINDS CONTINUING TO THE WEST...BECOMING VARIABLE WEST OF THE BLUE RIDGE AFT 00Z. WITH WEDGE DEVELOPING AND DRY AIR STILL WELL UPSTREAM THROUGH THE TAF VALID PERIOD...EXPECT MVFR CIGS/VSBYS IN BR/-DZ AFT 00Z EAST OF THE BLUE RIDGE...WITH POTENTIAL GROUND FOG DEVELOPING WEST OF THE BLUE RIDGE BECAUSE OF SATURATED GROUND AND LATE DAY -SHRA. LOW TO MEDIUM CONFIDENCE IN CIGS/VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND/SPD THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN TSRA POTENTIAL WEST OF THE BLUE RIDGE AFT 18Z. EXTENDED AVIATION... EXPECT FLYING CONDITIONS TO SLOWLY IMPROVE SUNDAY AS HIGH PRESSURE CONTINUES TO BUILD IN FROM THE NORTHEAST. WILL SEE A FEW SHOWERS DEVELOP SUNDAY AFTERNOON...MAINLY WEST OF THE BLUE RIDGE...HOWEVER THE MAIN CONCERN WILL BE EARLY MORNING FOG AND STRATUS. STRATUS WILL BE SLOW TO BURN OFF THROUGH THE DAY...ALTHOUGH BREAKS WILL DEVELOP DURING THE AFTERNOON. A BETTER PUNCH OF DRY AIR WITH HIGH PRESSURE BUILDING IN FROM THE NORTHEAST MAY BE ENOUGH WITH MIXING/HEATING TO ALLOW FOR INCREASING VFR CONDITIONS MONDAY INTO TUESDAY UNDER MAINLY DRY CONDITIONS. && .EQUIPMENT... THE ASOS AT LYNCHBURG (LYH) VA REMAINS PARTIALLY INOP DUE TO A BOARD FAILURE. PARTS HAVE BEEN ORDERED WITH THE RETURN OF COMPLETE SERVICE UNKNOWN AT THIS TIME. THE NOAA WEATHER RADIO AT WYTHEVILLE VA...WZ2500...BROADCASTING ON A FREQUENCY OF 162.450 MHZ IS OFF THE AIR. VERIZON HAS BEEN CONTACTED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...RAB NEAR TERM...RAB SHORT TERM...DS LONG TERM...AMS AVIATION...NF/RAB EQUIPMENT...RAB/WP

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