Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 232327 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 727 PM EDT WED JUL 23 2014 .SYNOPSIS... A COLD FRONT WILL APPROACH THE AREA FROM THE NORTHWEST TONIGHT AND CROSS THE MID ATLANTIC REGION THURSDAY. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE FRONTAL PASSAGE. DRIER AIR WILL MOVE INTO THE AREA BEHIND THE FRONT FRIDAY WITH A DAY OR TWO OF DRY WEATHER...FRIDAY INTO SATURDAY. MOISTURE WILL QUICKLY RETURN OVER THE WEEKEND WITH HEAT AND HUMIDITY HELPING TO TRIGGER MORE THUNDERSTORM ACTIVITY. A STRONG FRONT IS EXPECTED TO CROSS THE AREA LATE SUNDAY INTO MONDAY. && .NEAR TERM /THROUGH THURSDAY/... AS OF 445 PM EDT WEDNESDAY... SCATTERED THUNDERSTORMS DEVELOPING MAINLY ALONG THE BLUE RIDGE LATE THIS AFTERNOON IN THE WARM AND HUMID AIR MASS WITH SURFACE DEWPOINTS NEARING 70F AND PLENTY OF INSTABILITY. A FEW STORMS COULD BE SEVERE ALONG WITH BRIEF HEAVY RAINFALL WITH ATTENDANT LOCAL RUNOFF ISSUES. SHOULD SEE CONVECTION DIMINISH WITH LOSS OF HEATING LATER THIS EVENING. NEXT QUESTION WILL BE PRECIPITATION CHANCES LATER TONIGHT AND INTO TOMORROW IN ASSOCIATION WITH APPROACHING COLD FRONT AS UPPER TROUGH AMPLIFIES OVER THE GREAT LAKES. FRONTAL BOUNDARY WILL MAKE ITS WAY TOWARD THE WESTERN CWA BY THU MORNING...AND MODELS DEVELOP FAIRLY WIDESPREAD COVERAGE OF PRECIP ACROSS THE WEST EARLY TOMORROW AND SPREADING EAST ACROSS THE PIEDMONT AS THE DAY PROGRESSES. THUNDER MAY BE LIMITED BY CLOUD COVER AND LACK OF INSTABILITY ESPECIALLY ACROSS THE WESTERN HALF OF THE CWA BUT OVERALL CHANCES FOR CONVECTION WILL INCREASE OVER THE PIEDMONT LATER IN THE DAY WITH POSSIBLY SOME HEATING AND MORE INSTABILITY. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE AS WELL WITH STILL VERY HIGH PWATS AHEAD OF THE FRONT. CLOUD COVER AND HIGH DEWPOINTS WILL KEEP LOWS TONIGHT WELL ABOVE NORMAL RANGING FROM MID 60S TO LOWER 70S...WITH DIURNAL RANGE LIMITED TOMORROW AS WELL. HIGHS SHOULD BE 5 TO 8F LOWER THAN TODAYS WARM VALUES. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... AS OF 500 PM EDT WEDNESDAY... SURFACE COLD FRONT IS EXPECTED TO SLIP SOUTHEAST OF OUR AREA THURSDAY NIGHT BEFORE STALLING ALONG THE CAROLINA COAST FRIDAY. MODELS MAINTAIN CONTINUITY WITH DRY HIGH PRESSURE BUILDING INTO THE FORECAST AREA FROM THE NORTH. IN SPITE OF THE DRY AIR...THICKNESSES DO NOT FALL THAT MUCH...SO DO NOT EXPECT MUCH IN THE WAY OF A TEMPERATURE CHANGE. IF ANYTHING...INCREASED SUNSHINE WILL HELP BOOST SURFACE TEMPERATURES TO AT LEAST OUR JULY NORMALS FRIDAY...THEN BEGIN WARMING BACK UP SATURDAY AS SOUTHERLY FLOW INCREASES BEHIND THE DEPARTING SURFACE HIGH. FOR SATURDAY...MOISTURE WILL BEGIN TO RETURN TO THE FORECAST AREA FROM THE SOUTH AND SOUTHWEST. CAN`T RULE OUT A LATE AFTERNOON POPUP SHOWER OVER THE MOUNTAINS...BUT THINK MOST AREAS WILL REMAIN DRY UNTIL THE ARRIVAL OF A FRONT LATE IN THE WEEKEND. WILL HAVE TO MONITOR THIS UPSTREAM FRONT CLOSELY AS IT MAY CAST SOME PREFRONTAL SHOWERS AND STORMS OUR WAY AS EARLY AS SATURDAY NIGHT. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 515 PM EDT WEDNESDAY... STRONG COLD FRONT IS SLATED TO CROSS THE FORECAST AREA LATE SUNDAY INTO MONDAY...ASSOCIATED WITH A VIGOROUS SHORT WAVE TROUGH THAT WILL BE MOVING ACROSS THE GREAT LAKES AND OHIO VALLEY. THIS PARTICULARLY STRONG DISTURBANCE...NOTED BY ALL THE MODELS...PROMISES TO AMPLIFY THE EASTERN LONG WAVE TROUGH...A PATTERN THAT WILL NET COOLER THAN NORMAL TEMPERATURES FOR SEVERAL DAYS NEXT WEEK. DURING THE TRANSITION SUNDAY INTO MONDAY...INCREASED INSTABILITY AHEAD OF THE FRONT ALONG WITH STRONG DYNAMIC FORCING WILL RESULT IN POTENTIAL FOR STRONG TO SEVERE STORMS. THE OPPORTUNITY WILL EXIST FOR ORGANIZED DEEP CONVECTION WITH POTENTIAL FOR A MESOSCALE CONVECTIVE SYSTEM (MCS) TO CROSS THE FORECAST AREA FROM THE WEST. ATTM WILL MAINTAIN THE BEST CHANCE FOR SHOWERS/STORMS SUNDAY...WITH THE THREAT LINGERING INTO MONDAY UNTIL THE SURFACE FRONT CAN COMPLETELY CLEAR THE FORECAST AREA. GENERALLY FOLLOWED HPC GUIDANCE THROUGH THE PERIOD TRENDING POPS DOWNWARD AFTER THE EARLY WEEK FROPA. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... AS OF 725 PM EDT WEDNESDAY... WIDELY SCATTERED CONVECTION IS BEGINNING TO WEAKEN WITH THE LOSS OF HEATING. FOR THE VERY SHORT TERM...THROUGH 01Z...STORMS MAY MOVE OVER KDAN. OTHERWISE...VCTS WAS CARRIED FOR THE OTHER TAF SITES. MEANWHILE...AN UPPER LEVEL SHORT WAVE MOVING ACROSS THE LOWER OHIO VALLEY HAS TRIGGERED A CLUSTER OF STORMS ACROSS EASTERN KENTUCKY THIS EVENING. THIS AREA OF SHOWERS AND STORMS WILL GRADUALLY DIMINISH THIS EVENING...BUT NOT COMPLETELY DISSIPATE. AS A RESULT...WIDELY SCATTERED STORMS MAY MOVE BACK INTO OUR AREA LATE TONIGHT...BEFORE DIMINISHING DURING THE PRE-DAWN HOURS. PATCHY FOG IS AGAIN POSSIBLE AT KLWB AND KBCB LATE TONIGHT WITH ABUNDANT LOW LEVEL MOISTURE AND LIGHT WINDS. THE COVERAGE OF THE FOG SHOULD BE WIDESPREAD DUE TO A BLANKET OF VFR CLOUDS. STORMS WILL RE-DEVELOP EARLY TOMORROW AS A COLD FRONT MOVES THROUGH THE AREA. THE COVERAGE OF THE CONVECTION IS NOT EXPECTED TO BE WIDESPREAD ENOUGH TO INCLUDE IN THE TAF SITES...BUT DID ADD A VCTS AT ALL TAF SITES. THREAT FOR PRECIPITATION SHOULD END EARLY IN THE AFTERNOON IN THE WEST AS THE FRONT EXITS THE FORECAST AREA BETWEEN 18Z THUR AND 00Z FRI...LEAVING VFR CONDITIONS. EXTENDED AVIATION DISCUSSION... AIRMASS WILL DRY OUT BEHIND THE FRONT GOING INTO FRIDAY- SATURDAY. OVERALL EXPECT SUB VFR AT TIMES THURSDAY WITH SHRA/TSRA AND MAYBE SOME FOG THU NIGHT...FOLLOWED BY VFR FRI- SAT OUTSIDE OF ANY VALLEY FOG AT KLWB/KBCB EACH MORNING. && .EQUIPMENT... AS OF 715 PM EDT WEDNESDAY... KFCX RADAR IS BACK UP AND IS OPERATING AT FULL STRENGTH. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...PC/WP SHORT TERM...PM LONG TERM...PM AVIATION...PC/PH EQUIPMENT...PM

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