Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300708 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 308 AM EDT SAT MAY 30 2015 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL MAINTAIN A VERY WARM AND HUMID AIRMASS ACROSS THE REGION TODAY INTO SUNDAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE IN THE WEEKEND...BEFORE PUSHING SOUTH OF THE AREA BY MONDAY...RESULTING IN MORE WIDESPREAD SHOWERS AND THUNDERSTORMS LATER SUNDAY INTO MONDAY AFTERNOON. COOLER WEATHER UNDER HIGH PRESSURE WILL BUILD IN BY THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 222 AM EDT SATURDAY... ISOLATED SHOWERS HAVE FINALLY ALL BUT FADED ACROSS THE REGION EARLY THIS MORNING LEAVING MORE PATCHY FOG AND LOW/MID CLOUDS TO INIT. HOWEVER AGAIN EXPECTING THIS MOISTURE TO QUICKLY BURN OFF THIS MORNING LEADING TO ANOTHER RATHER HOT AND HUMID AFTERNOON AS UPPER HEIGHTS ACTUALLY RISE JUST A BIT FROM THE EAST DURING THE DAY. THIS SHOULD ALLOW AN AREA OF WEAK SUBSIDENCE THAT WAS TO THE SE ON FRIDAY TO PUSH NORTH/NW AND PUT MORE OF A LID ON CONVECTION GIVEN FORECAST DRYING ALOFT OFF SOUNDINGS. LATEST GUIDANCE ALSO SHOWING A DROP IN PWATS THIS AFTERNOON WITH MORE OF A SOUTHERLY TRAJECTORY DEVELOPING AHEAD OF THE NEXT 5H TROUGH TO THE WEST. APPEARS BEST WEAK CONVERGENCE TO TAKE PLACE OVER THE NW WHERE SLIGHTLY BETTER RESIDUAL MOISTURE UNDER A LEFTOVER WEAKNESS ALOFT MAY ACT TO ENHANCE LIFT A BIT MORE TO PRODUCE A SCATTERING OF CONVECTION. THIS IN LINE WITH MOST SOLUTIONS AND ESPCLY THE LATEST NCAR ENSEMBLE AND HRRR BUT STILL NO MORE THAN CHANCE POPS AT BEST. ELSEWHERE CANT TOTALLY RULE OUT AT LEAST ISOLATED SHRA/TSRA PER HEATING...DECENT INSTABILITY...AND HIGH 85H THETA-E WITH BEST CHANCES MOUNTAINS WHERE AIDED BY OROGRAPHICS ESPCLY BLUE RIDGE. SHOULD BE ONE OF THE WARMEST DAYS SO FAR THIS SEASON GIVEN A WARM START AND LESS EXPECTED CLOUDS/TSRA THIS AFTERNOON. AGAIN APPEARS MOS A BIT COOL AS SEEN OVER THE PAST COUPLE OF DAYS AS THICKNESS SUGGESTS HIGHS CLOSE TO 90 SE...WITH LOW/MID 80S ELSEWHERE OUTSIDE OF THE HIGHEST ELEVATIONS. ANY EVENING CONVECTION MAY LINGER ESPCLY MOUNTAINS AN HOUR OR TWO AFTER SUNSET BEFORE LOSS OF HEATING AND LACK OF FORCING CAUSE SHOWERS TO FADE SO WILL KEEP SOME LOW POPS GOING THIS EVENING MAINLY FAR WEST. UPSTREAM PRE-FRONTAL SHRA/TSRA WILL THEN BE THE MAIN CONCERN OVERNIGHT BUT APPEARS MUCH OF THIS TOO FAR WEST TO REACH THE REGION BY DAYBREAK SUNDAY. HOWEVER RETURN OF DEEPER MOISTURE AHEAD OF THE TROUGH/FRONT AS SEEN IN MODEL PWATS LATE SUPPORTS INCLUDING SOME ISOLATED TO LOW CHANCE POPS MAINLY WESTERN THIRD LATE. OTHERWISE MAINLY PC WITH ADDED PATCHY FOG BY MORNING. TEMPS TO REMAIN ON THE WARM/MUGGY SIDE WITH MOST SPOTS ONLY FALLING INTO THE 60-66 RANGE. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... AS OF 245 AM EDT SATURDAY THE MEDIUM RANGE MODELS ARE ALL IN CONSENSUS THAT A SFC COLD FRONT.. ASSOCIATED WITH AN UPPER TROUGH MOVING THROUGH THE EASTERN GREAT LAKES INTO NEW ENGLAND...MOVES THROUGH OUR FORECAST AREA MONDAY. HOWEVER...THE MORE NOTICEABLE DRIER AIR AND COOLER TEMPS ARRIVE MONDAY NIGHT/EARLY TUESDAY ONCE SOUTHERN STREAM ENERGY AND ASSOCIATED SFC WAVE LIFT EAST. THE FORECAST AREA WILL REMAIN FIRMLY ENTRENCHED IN THE WARM SECTOR SUNDAY. WHILE INSTABILITY WILL INCREASE AS HIGHER PWAT AIR RETURNS...BEST SHEAR AND UPPER LEVEL DYNAMICS REMAIN NORTH AND WEST OF THE FORECAST AREA THROUGH SUNDAY. WHILE AN ISOLATED SEVERE STORM IS POSSIBLE...GREATER CONCERN MAY BE WITH LOCALLY HEAVY DOWNPOURS. WITH THE SLOWER ARRIVAL OF THE FRONT...PUSHED UP TEMPS A COUPLE OF DEGREES FOR HIGHS...ESPECIALLY IN THE EAST. KEPT POPS GOING AFTER SUNDOWN SUNDAY WITH FORCING FROM SFC BOUNDARY MOVING INTO THE AREA. WENT ABOVE GUIDANCE FOR LOWS SUNDAY NIGHT DUE TO CLOUDS AND SOME MIXING. PRECIPITATION MAY BE MORE WIDESPREAD MONDAY...ESPECIALLY IN THE SOUTHERN HALF OF THE FORECAST AREA...AS SFC BOUNDARY SLOWS SOMEWHERE IN THE EASTERN PORTION OF THE FORECAST AREA DUE TO A SFC WAVE FROM SOUTHERN STREAM ENERGY DEVELOPING IN NC. EXPECT MORE CLOUD COVER AND SLIGHTLY COOLER TEMPS ON MONDAY...AS A RESULT...LOWER INSTABILITY. THE EXCEPTION WOULD BE IN ADVANCE OF THE FRONT...IN THE FAR EASTERN PORTION OF THE FORECAST AREA WHERE AN ISOLATED SEVERE STORM CANNOT BE RULED OUT. DRIER/COOLER AIR FINALLY SURGES INTO THE FORECAST AREA MONDAY NIGHT AND TUESDAY. LEANED TOWARD THE COOLER GUIDANCE VALUES DURING THIS PERIOD. WHILE THE SFC BOUNDARY PUSHES SOUTH OF THE FORECAST AREA BY TUESDAY...850MB THETA-E AXIS LINGERS IN NC AND SOUTHERN VA AND WEAK OVERRUNNING WILL KEEP THE THREAT FOR SHOWERS FOR THIS AREA. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... AS OF 245 PM EDT FRIDAY... THE COLD FRONT WILL WASH OUT OVER OR JUST SOUTH OF THE AREA BY TUESDAY AFTERNOON. AFTER THIS POINT...THE REGION WILL START TO TRANSITION BACK A SOUTHERLY FLOW PATTERN AS A LOW/TROUGH DEVELOPS ACROSS THE LOWER MISSISSIPPI RIVER VALLEY...AND HIGH PRESSURE BECOMES CENTERED AGAIN OFF THE COAST OF THE CAROLINAS. DAYTIME HEATING ALONG WITH PIECES OF ENERGY EJECTING OFF THE LOWER MISSISSIPPI VALLEY LOW WILL HELP YIELD INCREASING CHANCE OF SHOWERS AND STORMS AGAIN BY THURSDAY INTO FRIDAY. TEMPERATURES WILL ALSO START TO TREND MILDER THURSDAY INTO FRIDAY. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... AS OF 1240 AM EDT SATURDAY... STILL SEEING ISOLATED SHRA LINGER ALONG THE BLUE RIDGE GIVEN LEFTOVER INSTABILITY BUT EXPECTING MOST RAINFALL TO DISSIPATE OVER THE NEXT COUPLE OF HOURS WITH COOLING OVERNIGHT. MAY NEED TO INCLUDE A VCSH MENTION PENDING LOCATION OF SHRA AT RELEASE OTRW LEAVING OUT MENTION OVERNIGHT. OTHERWISE...PREVIOUS FORECAST THINKING CONCERNING THE DEVELOPMENT OF MVFR OR IFR FOG LATER TONIGHT IN AREAS THAT RECEIVED RAIN EARLIER TODAY STILL SEEMS REASONABLE...AND THIS SUPPORTED BY LATEST LAMP GUIDANCE. KLWB...KLYH...AND KBCB HAVE THE GREATEST POTENTIAL FOR DEVELOPMENT OF LATE NIGHT VISIBILITY RESTRICTIONS...LESS SO AT KDAN...KBLF...AND KROA. HOWEVER STILL QUITE UNCERTAIN AS TO HOW LOW VSBYS WILL GO GIVEN PATCHY NATURE TO FOG AND LINGERING STRATO-CU/AC THAT COULD HINDER FOG DEVELOPMENT SIMILAR TO LAST NIGHT. FOR NOW ADDED IN BRIEF TEMPO GROUPS FOR LOWER VSBYS AT KBCB/KLWB WHERE COULD SEE A PERIOD OF LIFR AROUND DAYBREAK. SIMILAR TO FRIDAY MORNING...EXPECT MOST LATE NIGHT FOG TO DISSIPATE BY 13Z/9AM...TO BE QUICKLY FOLLOWED BY DEVELOPMENT OF CUMULUS WITH ONSET OF SURFACE HEATING. HOWEVER...UNLIKE FRIDAY...EXPECT SOME SUBSIDENCE NUDGING IN FROM THE SOUTHEAST SUCH THAT ANY DIURNAL REDEVELOPMENT OF SHOWERS/STORMS BY LATE MORNING/EARLY AFTERNOON EXPECTED TO BE LESS IN OVERALL COVERAGE AND MAINLY CONFINED TO SOUTHEAST WEST VIRGINIA. THEREFORE...VCTS COMMENT KEPT AT KBLF AND KLWB TERMINAL FORECAST POINTS AT 17Z/1PM...BUT NOT AT THE REMAINING AVIATION FORECAST POINTS. EXTENDED DISCUSSION... ON SUNDAY...A MOIST UNSTABLE AIR MASS WILL REMAIN IN PLACE ACROSS THE REGION WITH ONLY WEAK FORCING. THIS WILL RESULT IN MAINLY SLOW MOVING DIURNALLY DRIVEN DEEP CONVECTION DURING THE AFTERNOON AND EVENING HOURS FOLLOWED BY STABLE CONDITIONS AND PATCHY MVFR FOG AT NIGHT. A FRONTAL SYSTEM WILL APPROACH FROM THE NORTH SUNDAY NIGHT. THIS BOUNDARY SHOULD FINALLY SINK SOUTH INTO THE REGION BY MONDAY RESULTING IN WIDESPREAD CONVECTION...WITH ADDITIONAL ROUNDS OF SHRA/TSRA INTO AT LEAST MONDAY NIGHT BEFORE THE BOUNDARY SINKS TO THE SOUTH. THIS SHOULD MAKE FOR MORE FREQUENT PERIODS OF SUB-VFR FROM SUNDAY NIGHT INTO TUESDAY MORNING WITH LOWER CIGS/VSBY REDUCTIONS DUE TO SHOWERS/STORMS DURING THE DAY...AND IN FOG OVERNIGHT INTO THE EARLY MORNING HOURS EACH DAY. LOWER MVFR/IFR CIGS ARE LIKELY BEHIND THE FRONT ON TUESDAY AND WEDNESDAY WITH EASTERLY FLOW AND WEDGING IN PLACE RESULTING IN MVFR CEILINGS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/JH NEAR TERM...JH SHORT TERM...PH LONG TERM...DS AVIATION...AMS/JH/WERT

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