Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 241746 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 146 PM EDT THU JUL 24 2014 .SYNOPSIS... A COLD FRONT ACROSS THE AREA TODAY WILL SHIFT SLOWLY SOUTHEAST BY LATE TONIGHT. HIGH PRESSURE OVER THE MIDWEST WILL BUILD ACROSS THE MID-ATLANTIC THROUGH FRIDAY. OVER THE WEEKEND THE PATTERN SETS UP FOR POTENTIAL UPPER DISTURBANCES MOVING INTO THE REGION ON A NORTHWEST FLOW. A STRONG FRONT IS EXPECTED TO CROSS THE AREA MONDAY. && .NEAR TERM /THROUGH FRIDAY/... AS OF 130 PM EDT THURSDAY... FAIRLY WIDESPREAD CONVECTION DEVELOPING ABOUT ON SCHEDULE EARLY THIS AFTERNOON. ACTIVITY SHOULD CONTINUE FOR NEXT SEVERAL HOURS AS SHORT-WAVE CROSSES THE MOUNTAINS AND COLD FRONT REMAINS DRAPED ACROSS THE CWA. WITH UNSTABLE AND WARM MOIST AIR IN PLACE A FEW STORMS COULD BECOME SEVERE WITH WIND AND HAIL THREAT. PREVIOUS VALID DISCUSSION... AS OF 1000 AM THURSDAY... HIGH-RES WRF HAD DECENT HANDLE ON INITIALIZATION WITH BULK OF EARLY MORNING LOCATED ACTIVITY EAST OF THE CWA AND SHOWING ADDITIONAL FAIRLY WIDESPREAD COVERAGE BEGINNING AROUND 18Z. RAMPED UP POPS TO LIKELY MOST AREAS BY THEN 18-19Z BUT MODEL SHOWS PRECIP SHIFTING EAST FAIRLY RAPIDLY AS THE FRONT SAGS FURTHER SOUTHEAST. HPC QPF GENERALLY 0.25 TO 0.50 INCHES BUT VERY UNEVEN AS USUAL WITH A FEW AREAS GETTING BRIEF HEAVY DOWNPOURS AND OTHERS NONE AT ALL. SPC ALSO SHIFTED SLIGHT RISK OF SVR BACK INTO PORTIONS OF SOUTHERN CWA...WHICH MIGHT DEPEND ON GETTING SOME BREAKS IN OVERCAST TO HELP GENERATE MORE INSTABILITY ALONG WITH WHATEVER THE FRONT CAN PROVIDE IN THE WAY OF A TRIGGER. FRONTAL BOUNDARY ANALYZED ACROSS THE NORTHERN CWA AT THIS MORNING WITH 14Z OBS NORTH OF THE BOUNDARY SHOWING A SUBTLE WIND SHIFT TO NORTHERLY BUT WITH DRIER AIR IS STILL WELL BACK TO THE WEST ACROSS THE OH RIVER VALLEY WHERE MID-50S DEWPOINTS CAN BE FOUND. STILL UPPER 60S TO LOWER 70S DEWPOINTS ACROSS THE CENTRAL AND SOUTHERN CWA. THIS FRONT COULD BECOME THE FOCUS FOR STORM DEVELOPMENT LATER TODAY...ALONG WITH RESIDUAL OUTLFOW BOUNDARIES WHICH MAY EXIST. FORECAST HIGHS TODAY BASICALLY UNCHANGED WITH READINGS RANGING FROM THE MID 70S WEST TO MID 80S EAST. PREVIOUS VALID DISCUSSION... AS OF 330 AM THURSDAY... TONIGHT...THE MAIN AXIS OF LIFT AND MOISTURE SHIFTS EAST OF AREA WITH SKIES STARTING TO CLEAR IN THE WEST. WILL KEEP HIGH CHANCE EARLY IN THE EAST THEN DRY IT OUT BY MIDNIGHT/EARLY OVERNIGHT...WHEN MAIN TROUGH AXIS AT 5H SHIFTS ACROSS. LESS HUMID AIR WILL PUSH INTO THE MOUNTAINS AT LEAST THOUGH PROXIMITY OF FRONT THAT STALLS OVER ERN NC/SC MAY INHIBIT THE LOWER DEWPOINTS REACHING THE SE CWA UNTIL FRIDAY. LOWS ARE GOING TO RANGE FROM THE MID 50S ACROSS THE HIGHER MTNS TO MID 60S SOUTHEAST. FRIDAY WILL BE DRY AND LESS HUMID WITH HIGH PRESSURE NOSING IN FROM THE MID ATLANTIC TURNING WINDS AROUND MORE TO THE NE-E. HIGHS RANGING FROM THE UPPER 70S MTNS TO LOWER 80S ROANOKE TO MID 80S EAST CAN BE EXPECTED. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... AS OF 350 AM EDT THURSDAY... 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 MONDAY. 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 /18Z THURSDAY THROUGH TUESDAY/... AS OF 135 PM EDT THURSDAY... FAIRLY WIDESPREAD CONVECTION AFFECTING ALL MOUNTAIN TAF SITES EARLY THIS AFTERNOON WITH VCTS OT TEMPO COVERAGE. CONVECTION MOVING EAST AT 10-15 MPH BUT CONDITIONS WILL BE HIGHLY VARIABLE OVER THE NEXT SEVERAL HOURS. SHOULD EXIT THE MOUNTAINS BY 22-23Z AND DAN/LYH BY 00-01Z. FOG LIKELY TO BE AN ISSUE AT MOST SITES OVERNIGHT DEPENDING ON LOCAL RAINFALL AND SPEED OF DRY AIR ARRIVAL. THINK LWB/BCB WILL HAVE DENSE FOG BEFORE SUNRISE FOR A FEW HOURS AND REDUCED VSBYS AT OTHER SITES POSSIBLE. EXTENDED AVIATION DISCUSSION... AIRMASS WILL DRY OUT BEHIND THE FRONT GOING INTO FRIDAY- SATURDAY. VFR FRI- SAT OUTSIDE OF ANY VALLEY FOG AT KLWB/KBCB EACH MORNING. ANOTHER FRONT AND ASSOCIATED UPPER IMPULSES COULD BRING A GOOD THREAT OF STORMS IN THE SUN-MON TIME FRAME. DURING THIS TIME MAINLY VFR...EXCEPT IN TSRA AND FOR ANY LATE NIGHT FOG. && .HYDROLOGY... U.S. DROUGHT MONITOR ISSUED THIS MORNING AND VALID THROUGH 12Z TUESDAY JULY 22 SHOWED EXPANSION OF THE EXISTING ABNORMALLY DRY CONDITIONS INTO MOST OF OUR SE WV COUNTIES AND FAR WESTERN VA...MAINLY THE UPPER JAMES RIVER BASIN. 30-DAY RAINFALL DEFICITS IN MUCH OF THIS AREA ARE RUNNING 2 TO 3 INCHES OR ONLY 25 TO 50 PERCENT OF NORMAL AND 60-DAY RAINFALL NUMBERS NOT MUCH BETTER. JULY IS CLIMATOLOGICALLY THE WETTEST MONTH IN OUR CWA WITH AN AVERAGE OF RANGING FROM 4 TO 5 INCHES. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...PC/WP SHORT TERM...PM/WP LONG TERM...PM AVIATION...PC/WP HYDROLOGY...PC

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