Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 290538 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 138 AM EDT MON SEP 29 2014 .SYNOPSIS... HIGH PRESSURE CENTERED JUST NORTH OF THE REGION WILL WEAKEN TONIGHT. LOW PRESSURE DEVELOPING ALONG THE CENTRAL GULF COAST WILL MOVE NORTHEAST TONIGHT INTO MONDAY...BRINGING WIDESPREAD CLOUD COVER AND A PERIOD OF LIGHT RAIN. FOR OUR REGION RAINFALL FROM THIS SYSTEM IS EXPECTED TO BE LESS THAN A QUARTER OF AN INCH. THE HEAVIER RAINS WILL FALL TO OUR SOUTH. && .NEAR TERM /THROUGH TODAY/... AS OF 100 AM EDT MONDAY... WEAK HIGH PRESSURE REMAINS SITUATED OVER US WITH LIGHT RAIN SHOWERS MOVING NWD INTO THE NC FOOTHILLS...ALONG WEAK THETA-E GRADIENT. FORECAST UPDATED TO REFLECT LOWER POPS NORTH OF THE VA/NC BORDER AND SLIGHTLY HIGHER IN THE NC FOOTHILLS/MOUNTAINS THROUGH DAWN. NO OTHER MAJOR CHANGES MADE TO THE FORECAST WITH THIS UPDATE. PREVIOUS VALID DISCUSSION... A STATIONARY FRONT WHICH HAS BEEN OVER THE GULF OF MEXICO THE LAST COUPLE OF DAYS WILL BE THE FOCUS FOR DEVELOPING LOW PRESSURE. MODELS ARE IN AGREEMENT THIS SURFACE LOW WILL TRACK EAST-NORTHEAST PASSING OFF THE FLORIDA/GEORGIA COAST MONDAY NIGHT...AND NEVER GAINING MUCH LATITUDE. AS SUCH...FOR OUR FORECAST AREA THIS MEANS LESS RAINFALL THAN ANTICIPATED WITH AN OVERALL DOWNWARD TREND IN QPF COMPARED TO PREVIOUS FORECASTS. STILL THINK THERE WILL BE AN OPPORTUNITY FOR LIGHT RAIN MONDAY...JUST NOT A LOT OF QPF...GENERALLY A TENTH OF AN INCH OR LESS ON THE AVERAGE. FOR TONIGHT...CLOUDS WILL CONTINUE TO INCREASE AND THICKEN AS THE STORM SYSTEM GETS MORE ORGANIZED ALONG THE GULF COAST. DEEPER MOISTURE WILL BE FLOWING NORTH WITH TIME...RAIN OVERSPREADING THE SOUTHEAST STATES DURING THE OVERNIGHT. THE WEDGE OF DRY AIR WHICH HAS BEEN DRIVEN DOWN THE EAST SIDE OF THE APPALACHIANS WILL LIKELY RESULT IN A FORK SHAPE TO THE DEVELOPING PRECIPITATION FIELD WITH RAIN DEVELOPING TO OUR WEST UP THROUGH THE TENNESSEE VALLEY...AND RAIN DEVELOPING TO OUR SOUTHEAST UP THROUGH THE PIEDMONT. BY DAYBREAK MONDAY...EXPECTATION IS FOR LIGHT RAIN IN OUR FAR WESTERN AND SOUTHWEST CWA. FOR THE DAY MONDAY...A BRIEF PERIOD OF SATURATION OF THE LOW LEVELS PROVIDING A PERIOD OF LIGHT RAIN TO THE AREA. THE HEAVIER RAINS WILL BE SKIRTING OUR REGION TO THE SOUTH...THE DEEPER MOISTURE MOVING FROM THE GULF COAST TO ALONG THE SOUTHEAST ATLANTIC BEACHES MONDAY NIGHT. GENERALLY FOLLOWED MOS TEMPS TONIGHT...BUT UNDERCUT THE HIGH TEMPERATURES MONDAY DUE TO DENSE CLOUD COVER. COOLEST READINGS && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... AS OF 345 PM EDT SUNDAY... SOME DRAMATIC CHANGES WITH THE 12Z MODELS COMPARED TO 24 HOURS AGO. MODELS HAVE LEANED TOWARDS THE GFS SOLUTION FOR MONDAY-MONDAY NIGHT WITH HEAVY RAIN POTENTIAL REMAINING SOUTH IN THE CAROLINAS. MODELS ARE TRACKING THE GULF DISTURBANCE EAST INSTEAD OF NORTHEAST AS A WEAK UPPER LEVEL TROUGH IS NOW FOLDED OVER THE NORTHERN MID ATLANTIC REGION SOUTH INTO THE TENNESSEE VALLEY. ALSO OVER THE FORECAST AREA IS A WEAK AREA OF HIGH PRESSURE WITH A WEDGE BOUNDARY CLOSER TO THE NC/SC BORDER. CONVECTION ALONG THIS BOUNDARY WILL MOVE EAST WHILE FLOW ALOFT IS RELATIVELY WEAK FURTHER LIMITING MOISTURE FROM ADVANCING NORTH. POPS FOR MEASURABLE RAINFALL ARE STILL VALID BUT THE AMOUNT AND DURATION OF RAIN WILL BE GREATLY REDUCE MONDAY NIGHT INTO TUESDAY MORNING. FROM TUESDAY INTO WEDNESDAY NIGHT...MODELS HAVE LEANED IN THE DIRECTION OF THE EURO...TRACKING A CLOSED LOW FROM THE GREAT LAKES TO OFF THE NEW ENGLAND COAST. THIS NORTHERN STREAM CLOSED LOW WILL PHASE WITH THE SOUTHERN STREAM GULF DISTURBANCE WEDNESDAY NIGHT...WELL OFF THE EAST COAST. SINCE BULK OF THE MOISTURE WILL BE WRAPPED CLOSE TO EACH LOW...RAIN CHANCE OVER THE FORECAST AREA ARE LOW. HOWEVER...MOISTURE WILL REMAIN ABUNDANT WITH A THETA-E RIDGE OVER THE REGION. LOW CLOUDS LIKELY TO REMAIN OVER THE AREA AND AS WINDS TURN TO THE EAST AS ANOTHER WEDGE OF HIGH PRESSURE BUILDS SOUTH...LIGHT RAIN/DRIZZLE IS POSSIBLE ALONG AND EAST OF THE BLUE RIDGE WEDNESDAY NIGHT INTO THURSDAY. DRIER WEATHER MEANS WARMER AFTERNOON TEMPERATURES. SINCE THE MODELS ARE KEEPING A WEDGE/EASTERLY FLOW IN THE AREA...BELIEVE MOS TEMPERATURES ARE TOO WARM. BOTH TUESDAY AND WEDNESDAY AFTERNOON...THE AREA SHOULD SEE UNIFORM TEMPERATURES IN THE 70S...JUST AT OR SLIGHT WARMER THAN NORMAL. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 345 PM EDT SUNDAY... SURFACE HIGH PRESSURE AND EASTERLY FLOW WILL REMAIN OVER THE REGION THURSDAY INTO FRIDAY MORNING. AN AXIS OF HIGH PRESSURE ALOFT MAY HELP SCOUR CLOUDS THURSDAY AFTERNOON AND EVENING...BEFORE THEY SPREAD BACK IN THURSDAY NIGHT. WITH AN EASTERLY FLOW AND MOISTURE...AREAS OF DRIZZLE AND/OR FOG IS POSSIBLE INTO FRIDAY MORNING. THE WEDGE WILL ERODE AND BREAK THROUGH THE DAY FRIDAY AS A COLD FRONT APPROACHES THE AREA LATE FRIDAY. PREFRONTAL SHOWERS WILL ENTER THE MOUNTAINS FRIDAY AFTERNOON THEN MOVE EAST OF THE BLUE RIDGE FRIDAY EVENING. MAJORITY OF THE RAIN /0.25/ WILL FALL OVER THE MOUNTAINS WITH LIGHTER AMOUNTS /0.10/ EAST OF THE BLUE RIDGE. WE DO EXPECTED SHOWERS TO ADVANCE EAST OF THE BLUE RIDGE AS WINDS BACK TO THE SOUTH AHEAD OF THE FRONT. INSTABILITIES ARE NOT LOOKING STRONG...THEREFORE MOSTLY SHOWERS WITH A FEW RUMBLES OF THUNDER FROM ELEVATED CONVECTION WITH THE FRONTAL PASSAGE. MODELS ARE ALSO MOVING THIS FRONT FASTER ACROSS THE REGION...CLEARING THE PIEDMONT BY EARLY SATURDAY MORNING. A STRAY MOUNTAIN SHOWERS IS POSSIBLE SATURDAY AFTERNOON AS AN UPPER LEVEL TROUGH/SHORT WAVE PIVOT ACROSS THE SOUTHERN OHIO VALLEY. WITH LITTLE TO NO GREAT LAKES TRAJECTORY...WE WILL JUST CALL SATURDAY A RAIN FREE DAY. HIGH PRESSURE BUILDS IN FROM THE SOUTHWEST SUNDAY. A WEAK PRESSURE GRADIENT WILL BRING BREEZY AND GUSTY CONDITIONS TO THE AREA OVER THE WEEKEND. SEASONAL TEMPERATURES THURSDAY WILL WARM ABOVE NORMAL ON FRIDAY...AHEAD OF THE COLD FRONT. ONCE THE FRONT PASSES EAST...SATURDAY AND SUNDAY HIGHS WILL RUN 5F-10F COOLER THAN NORMAL. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... AS OF 118 AM EDT MONDAY... THE MOISTURE SPREADING NWD INTO OUR AREA WILL BE MAINLY IN VFR IN TERMS OF CIGS. MODELS ARE KEEPING A HEAVIER QPF/RAIN TO THE SOUTH BUT STRETCH SOME LIGHT RAIN INTO THE AREA THIS MORNING ENDING BY LATE IN THE DAY OUT EAST. MOST TERMINALS WILL LIGHT RAIN TODAY BUT OBSCURATION TO VSBYS WILL BE MAINLY 6SM OR GREATER. UNTIL THEN THE HIGH CLOUDS MAY THIN OUT SOME IN LWB TO ALLOW FOR FOR DEVELOPMENT EARLY THIS MORNING...BUT CONFIDENCE ONLY MODERATE FOR MVFR. THROUGH THE DAY...CIGS WILL LOWER BUT STAY GENERALLY VFR...THOUGH BLF COULD DROP TO MVFR AFTER 17Z. WINDS WILL REMAIN LIGHT AND VARIABLE THROUGH THE PERIOD. MOST OF THE RAIN MOVES OUT MONDAY EVENING WITH POTENTIAL FOR FOG FORMATION LATE IN THE TAF PERIOD AT LWB/BLF...PERHAPS BCB. EXTENDED AVIATION DISCUSSION... LOW LVL MOISTURE ACROSS THE MOUNTAINS MONDAY NIGHT MAY LEAD TO SUB VFR CIGS AND VSBYS. IMPROVEMENT CAN BE EXPECTED TUESDAY- WEDNESDAY...THOUGH SOME LIGHT EASTERLY FLOW COULD LEAD TO SUB VFR CIGS/VSBYS ALONG/EAST OF THE BLUE RIDGE MIDWEEK. A COLD FRONT IS EXPECTED TO REACH US BY THE END OF NEXT WEEK WITH A THREAT OF SHOWERS AND POTENTIAL SUB VFR CONDITIONS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...AMS/PM/WP SHORT TERM...RCS LONG TERM...RCS AVIATION...NF/PM/WP

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