Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 040547 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 147 AM EDT WED MAY 4 2016 .SYNOPSIS... COLD FRONT CROSSES WEDNESDAY NIGHT. LARGE UPPER LEVEL LOW BRINGS COOL AND UNSETTLED WEATHER FOR THURSDAY THROUGH FRIDAY. WARM FRONT SATURDAY. ANOTHER COLD FRONT SUNDAY. && .NEAR TERM /THROUGH TODAY/... 1045 PM UPDATE... FCST ON TRACK ALTHOUGH THERE REMAINS A LOT OF UNCERTAINTY AS TO HOW EXTENSIVE BREAKS IN THE CLOUD COVER BECOME OVERNIGHT...AND HOW MUCH FOG FORMS AS A RESULT. FRONT AND ASSOCIATED SHOWERS OVER THE AREA CONTINUE TO DISSIPATE GRADUALLY. 800 PM UPDATE... ALLOWED THE SLIGHT CHANCE FOR SHOWERS ALONG THE FRONT ACROSS CENTRAL PORTIONS OF THE FORECAST AREA OVERNIGHT. PREV DISCN... THE GENERAL UPPER TROUGHING OVER THE OHIO VALLEY IS KEEPING WIDELY SCATTERED TO SCATTERED SHOWERS OVER THE AREA THIS AFTERNOON...BUT THESE ARE MAINLY FOCUSED NEAR THE DISSIPATING COLD FRONTAL BOUNDARY ACROSS CENTRAL WV. ONE DEFINED VORT MAX SEEN IN THE CLOUD FIELDS OVER EASTERN KENTUCKY...IN COMBINATION WITH DIURNAL HEATING...IS MOST LIKELY RESPONSIBLE FOR THE AFTERNOON SHOWERS. THIS FEATURE WILL SLOWLY MOVE EAST THROUGH TONIGHT...BUT WITH THE LOSS OF THE DIURNAL FACTOR...EXPECT SHOWERS TO MOSTLY DISSIPATE THIS EVENING...A BIT LATER IN THE MOUNTAINS. OTHERWISE...STILL LOTS OF MOISTURE HANGING AROUND UNDER THE GENERAL UPPER TROUGHING THROUGH TONIGHT...WHICH WILL LIKELY TRANSLATE INTO WIDESPREAD CLOUDS. FOG LATER TONIGHT WITH THE WET GROUNDS MAY BE ENHANCED BY ANY BREAKS IN THE CLOUDS...AND NEAR CALM WINDS UNDER WEAK HIGH PRESSURE BUILDING OVER THE AREA. IN SUMMARY...WILL END SHOWERS EARLY TONIGHT...KEEP LOTS OF CLOUDS...AND THROW IN SOME RIVER VALLEY FOG LATER TONIGHT. FOR WEDNESDAY...THE HIGH SHIFTS EAST EARLY WITH SOUTHWEST WINDS PICKING UP AHEAD OF AN APPROACHING COLD FRONT. THE GFS IS AGAIN THE FAST OUTLIER...SO WILL ACTUALLY KEEP THE FRONT JUST WEST OF THE AREA UNTIL NEAR 00Z. HOWEVER...A WELL DEFINED BAND OF SHOWERS ALONG AND AHEAD OF THE FRONT WILL MOVE INTO THE WESTERN HALF OF THE AREA DURING WEDNESDAY AFTERNOON. GOING WITH HIGH POPS WITH THIS FEATURE...AND WITH INSTABILITY AND LOWERING FREEZING LEVELS WITH ITS ASSOCIATED UPPER LOW DROPPING SOUTH FROM THE GREAT LAKES...HAVE INSERTED SMALL HAIL FOR THE AFTERNOON IN THE BAND OF SHOWERS/STORMS. FOR NOW...NOT ANTICIPATING WATER PROBLEMS WITH THE COLD FRONT SHOWERS NOR ANY SEVERE THUNDERSTORMS. TEMPERATURES WILL CONTINUE ON THE COOL SIDE WITH THE CHILLY PATTERN. && .SHORT TERM /TONIGHT THROUGH FRIDAY/... REALLY DIFFICULT TRYING TO TRACK THE FORCING AS A LATE SEASON CLOSED UPPER LEVEL LOW PINWHEELS TOWARDS THE CAROLINA COAST. COLD FRONT PASSES AT THE NEAR TERM/SHORT TERM BREAK...AND THEN IT APPEARS A NEW AXIS OF DEFORMATION SHOULD FORM ALONG OR NEAR THE MOUNTAINS THURSDAY AND THURSDAY NIGHT. WITH THE UPPER LOW ROTATING BACK TO THE NORTH INTO NEW ENGLAND...POPS WILL BE SLOW TO ERODE OVER THE EASTERN HALF OF THE CWA INTO THE FRIDAY TIME FRAME. FROM A FORECAST STANDPOINT...THE MAIN CHANGE IS THE INCREASE IN THE POPS TO THE LIKELY RANGE. LEANED ON THE NON CONVECTIVE MODELS FOR THIS SET UP...THAT IS...THE GFS AND ECMWF...AND LEAVE THE NAM OUT GIVEN A SOUTHWARD BIAS TO THE UPPER LOW. HAVE THUNDER IN THE FORECAST...AND GIVEN THE COLD POOL ALOFT WITH 500MB TEMPERATURES WELL BELOW -20C...SMALL HAIL COULD OCCUR IN ANY OF THE THUNDERSTORMS...EVEN IF LOW TOPPED ON THURSDAY. THUNDER POTENTIAL SHOULD BE SOMEWHAT DIURNALLY DRIVEN. PRECIPITABLE WATER VALUES SHOULD BE LOWER THAN 0.80 INCHES...SO THAT SHOULD LIMIT THE QPF A BIT. GOING BELOW GUIDANCE NUMBERS FOR MAX TEMPERATURES THURSDAY AS IT SEEMS THE COLD POOL IS BEING UNDERESTIMATED. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... USED AN BLEND OF THE OPERATIONAL MODELS AND ENSEMBLE MEANS FOR FRIDAY NIGHT INTO SATURDAY. THIS HAS THE UPPER LOW MOVING OFF TO THE EAST FRIDAY NIGHT. A WARM FRONT THEN PUSHES NORTHWARD THROUGH THE AREA ON SATURDAY...FOLLOWED BY ANOTHER COLD FRONT ON SUNDAY. FOR THE BEGINNING OF THE WORK WEEK...TRANSITIONED TO A BLEND OF THE ECMWF...CANADIAN...AND ECMWF ENSEMBLE MEAN. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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CEILINGS ARE STARTING TO FALL TO MVFR AND IN THE AREAS THAT WERE CLEAR WE ARE STARTING TO SEE SOME FOG DEVELOP. EKN HAS CLEARED OUT AND WITHIN AN HOUR THE VISIBILITY STARTED TO DROP...BELIEVE THAT THIS TREND WILL CONTINUE AND THEY WILL END UP WITH LIFR CONDITIONS THERE WITH FOG. MOST OTHER AREAS MAY SEE VSBY DROP TO MVFR OVERNIGHT ALONG WITH THE MVFR CIGS. IF A SOLID OVERCAST PERSISTS...THIS MAY NOT HAPPEN...BUT THE TREND THUS FAR HAS BEEN SIGHTS WAVERING BETWEEN BROKEN TO OVERCAST SKIES. ANY FOG WILL BURN OFF THIS MORNING AFTER SUNRISE...HOWEVER MVFR MORNING CIGS MAY PERSIST UNTIL LATER THIS AFTERNOON...BUT STILL NOT CERTAIN THAT WILL BE THE CASE AS FRONT APPROACHES LATER TODAY. A COLD FRONT WILL BRING SHOWERS AND THUNDERSTORMS BY LATE AFTERNOON AND EARLY THIS EVENING. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z THURSDAY... FORECAST CONFIDENCE: LOW TO MEDIUM. ALTERNATE SCENARIOS: CIGS WILL TEND TO VARY THROUGH THE MORNING HOURS WITH HOLES IN THE STRATOCU LAYER. MVFR FOG MAY NOT FORM AND ON THE OTHER HAND...HOLES IN THE OVERCAST MAY ALLOW IFR FOG TO FORM. FINALLY...HOW LONG MVFR CEILING LAST INTO THE DAYTIME HOURS IS STILL UNCERTAIN AT THIS TIME. THE TIMING OF SHOWERS AND THUNDERSTORMS ARRIVING FROM THE WEST ON THIS AFTERNOON MAY VARY AS MODELS STILL DIFFER. THUNDERSTORMS MAY BRING IFR CONDITIONS AND CONTAIN SMALL HAIL OR GRAUPEL WEDNESDAY AFTERNOON. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE WED 05/04/16 UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 EDT 1HRLY 02 03 04 05 06 07 08 09 10 11 12 13 CRW CONSISTENCY M M M M M M M M M M M H HTS CONSISTENCY H M M M M M M M H H H H BKW CONSISTENCY L L L L L L L L M M M M EKN CONSISTENCY L L L L L L L M M M M H PKB CONSISTENCY M M M M M M M M M M H H CKB CONSISTENCY M M M M M L L M M M M H AFTER 06Z THURSDAY... IFR POSSIBLE IN THUNDERSTORMS INTO WEDNESDAY EVENING AND AGAIN THURSDAY AFTERNOON.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...TRM/RPY/JMV/26 NEAR TERM...TRM/JMV/MPK SHORT TERM...26 LONG TERM...RPY AVIATION...MPK

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