Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 212324 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 624 PM EST SUN DEC 21 2014 .SYNOPSIS... WEAK HIGH PRESSURE EXITS THIS EVENING. SYSTEM CLIPS THE MOUNTAINS MONDAY. STRONG LOW PRESSURE SYSTEM LIFTS NORTHEAST ACROSS THE OHIO VALLEY THROUGH CHRISTMAS EVE. && .NEAR TERM /THROUGH MONDAY/... PREVIOUS FORECAST REMAINS REPRESENTATIVE. NO CHANGES NECESSARY. PREVIOUS DISCUSSION BELOW... HIGH PRESSURE AND LIGHT E FLOW HAD MANAGED TO ERADICATE THE STRATUS ALONG AND E OF THE OHIO RIVER TODAY. THIS HAS ALLOWED FOR DAYTIME HEATING BUT WILL ALSO ALLOW FOR RADIATIVE COOLING THIS EVENING. A WARM WAVE RIDES UP THE SE COAST LATE TONIGHT AND MON. THE QUESTION IS TO WHAT DEGREE THIS FLAT WAVE CAN THROUGH PRECIPITATION BACK INTO THE FCST AREA...AND WHEN WILL SUCH PRECIPITATION REACH THE GROUND GIVEN THE DRY MID LEVEL AIR TO START OUT WITH. MOST OF THE GUIDANCE SUGGESTS TEMPERATURES NEAR OR JUST BELOW FREEZING IN THE NRN WV MOUNTAINS...MAINLY ON THE HIGHER PEAKS AND DOWN THE ERN SLOPES INTO THE GREENBRIER VALLEY. MODELS DEPICT A WARM LAYER ALOFT WITH TEMPERATURES 1-2C IN THE H925-H85 LAYER. THIS SUGGESTS MELTING OF SNOW WHICH MEANS THERE COULD BE SLEET AND SNOW MIXED IN WITH ANY FREEZING RAIN. TEMPERATURES IN CLOUD SUPPORTIVE OF ICE CRYSTALS ARE LOST EARLY ON AS THE MOIST LAYER BECOMES MORE SHALLOW. THIS WOULD TEND THE PRECIPITATION BACK TOWARD FREEZING RAIN OR FREEZING DRIZZLE. THIS LEAVES THE TIMING OF THE ARRIVAL OF PRECIPITATION CRUCIAL AS TEMPERATURES SLOWLY CLIMB ABOVE FREEZING IN THE GREENBRIER VALLEY. CURRENT GRID DEPICTION IS FOR POPS CLIMBING ABOVE 50 YIELDING MEASURABLE QPF AS TEMPERATURES CLIMB. THIS LIMITS ICE ACCRETION TO AT MOST A HUNDREDTH AND NOT VERY WIDESPREAD. THE SREF DOES INTERSECT HIGH POPS WITH POCKETS OF HIGH PROBABILITIES FOR SFC TEMPERATURES AT OR BELOW FREEZING MON MIDDAY INTO THE AFTERNOON. COORD WITH WPC/WWD-PBZ-LWX-RNK ON ISSUANCE ADV FOR FREEZING RAIN POCAHONTAS COUNTY 11-17Z. THE REMAINDER OF THE FCST AREA SEES A RETURN OF CLOUD COVER TONIGHT...SETTING THE STAGE FOR ANOTHER GREY DECEMBER DAY...ALTHOUGH THE CLOUDS DO DECREASE BEHIND THE SYSTEM MON AFTERNOON. USED NEAR TERM...IN PARTICULARLY THE WRFNMM...RUC AND THE HRRR FOR TEMPERATURES TONIGHT AND NAM-BASED VALUES FOR THOSE ON MON...WHICH SHOULD FEATURE A MILDER AFTERNOON. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... 5H TROUGH TO DIG OVER THE MIDWEST WITH SEVERAL WAVES RIDING NWD ALONG THE COAST OF SE US. THIS LEAVES OUR CWA IN THE WARM SECTOR OF BAROCLINIC FORCING THAT WILL BE TAKING PLACE IN VARIOUS PHASES THROUGHOUT THE PERIOD. FIRST WEAKER WAVE DEFTLY EXITS TO THE EAST BY TUESDAY MORNING AND ONLY BROUGHT ISOLD AND LOW CHANCE POPS TO THE EASTERN MOUNTAINS. WAA WILL BE FULL SWING UNDER SOUTH TO SOUTHWEST FLOW AND CHANCES FOR ANY PRECIPITATION OF THE FROZEN VARIETY WILL BE NIL. A SECOND STRONGER WAVE WILL PUSH NORTH TUESDAY NIGHT AND WEDNESDAY. MODELS STILL SHOW POOR PHASING BETWEEN NORTHERN AND SOUTH STREAM SYSTEMS WITH MAIN SFC LOW DEVELOPMENT OCCURRING NORTH OF THE GREAT LAKES. THIS DELAYS FROPA AND ONSET OF CAA AND PLACES CWA SQUARELY IN THE WARM SECTOR THROUGH WEDNESDAY. FRONT WILL FINALLY PUSH THROUGH WEDNESDAY NIGHT WITH PRECIPITATION COMING TO AN END...MOSTLY BEFORE THE COLDER AIR ON BACKSIDE IS ABLE TO MOVE IN. THUS...ONLY HAVE VERY LIGHT SNOW AMOUNTS FIGURED FOR THE MOUNTAINS IN NORTHEASTERN COUNTIES. USED MAINLY SREF FOR TIMING ONSET OF PRECIP DEVELOPMENT. FOR TEMPS...USED BC GRIDS WITH A BLEND TOWARD INHERITED FORECAST TEMPS. && .LONG TERM /THURSDAY THROUGH SUNDAY/... COLD FRONT TO THE EAST OF THE CWA AT THE BEGINNING OF THE PERIOD...WITH A GRADUAL CHANGE OVER TO SNOW FOR CHRISTMAS EVE NIGHT AND CHRISTMAS DAY. AT THIS POINT...REALLY NOT EXPECTING MUCH IN TERMS OF SNOWFALL ACCUMULATIONS. WINDS HOWEVER ON THURSDAY ARE STILL EXPECTED TO BE GUSTY POST FRONTAL. AREA DRIES OUT THURSDAY EVENING AS THE LOW PULLS OFF TO THE NORTHEAST. HIGH PRESSURE THEN BRIEFLY BUILDS IN FOR A BREAK IN PRECIPITATION. ANOTHER COLD FRONT WILL DROP ACROSS THE AREA OVER THE WEEKEND...CREATING A CHANCE FOR LIGHT SNOW SHOWERS...AND WILL USHER IN MUCH COLDER AIR INTO THE REGION. TRENDED TEMPERATURES NEXT WEEKEND DOWN FROM PREVIOUS FORECAST. && .AVIATION /23Z SUNDAY THROUGH FRIDAY/... A WEAK WAVE OF LOW PRESSURE MOVES UP ALONG THE SE COAST OVERNIGHT TONIGHT AND MON...WITH RAIN LIKELY IN THE MOUNTAINS WHERE A WINTRY MIX PCPN IS FORECASTED THROUGH EARLY MONDAY MORNING. CONSEQUENTLY...VFR CONDITIONS EXPECTED TO PREVAIL TONIGHT INTO SUNDAY...WITH THE EXCEPTION OF BKW AND NEARBY CENTRAL MOUNTAINS WHERE LOW STRATUS SHOULD DEVELOP OVERNIGHT. EXPECT IFR CEILINGS SUPPORTED BY THE NAM AND LAV GUIDANCE INDICATING IFR CONDITIONS WITH BETTER CONFIDENCE FROM 15Z TO 18Z. DECIDED TO BRING EARLIER THE LOW STRATUS OVER BKW STARTING AROUND 09Z WHEN THE NAM SHOWS LOWER DEWPOINT DEPRESSION...AND BUFKIT SOUNDINGS SHOWS A MORE PRONOUNCED SATURATED LAYER AROUND 900 FEET. LOW CEILINGS AND IFR VISIBILITIES ALSO POSSIBLE ACROSS THE EASTERN SLOPES OF THE NORTHEAST MOUNTAINS ACCOMPANIED BY DRIZZLE OR FREEZING DRIZZLE OVERNIGHT INTO EARLY SUNDAY. EASTERLY FLOW COULD WILL GRADUALLY INCREASE OVERNIGHT ACROSS THE HIGHER ELEVATIONS AS SHOWN BY MODELS AT H925. FLOW WILL CONTINUE TO INCREASE FROM THE SOUTHEAST ON SUNDAY. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z TUESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING AND LOCATION OF A MVFR STRATUS DECK COULD VARY CONSIDERABLY OVERNIGHT INTO MON. 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. UTC 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07 EST 1HRLY 15 16 17 18 19 20 21 22 23 00 01 02 CRW CONSISTENCY M M H H H H H H H H H H HTS CONSISTENCY M M H H H H H H H H H H BKW CONSISTENCY H H H M M M M M L L L L EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY M M M M M H H H H H H H CKB CONSISTENCY M M M M H H H H H H H H AFTER 00Z TUESDAY... IFR POSSIBLE IN MOUNTAINS INTO EARLY MON EVENING IN A WINTRY MIX. IFR POSSIBLE IN RAIN TUE NT INTO WED...CHANGING TO SNOW SHOWERS WED NT...AS AN INTENSE LOW PRESSURE CENTER PASSES. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...FREEZING RAIN ADVISORY FROM 6 AM TO NOON EST MONDAY FOR WVZ046. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...TRM/RPY/SL/30 NEAR TERM...ARJ/TRM SHORT TERM...KMC LONG TERM...SL AVIATION...ARJ

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