Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 132002 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 302 PM EST SAT FEB 13 2016 .SYNOPSIS... HIGH PRESSURE BUILDS IN FOR OVERNIGHT. BITTER COLD AIR. STRONG WARM AIR ADVECTION SUNDAY INCREASES MOISTURE AND EVENTUALLY SNOW AT SURFACE. CONTINUED SOUTHERLY FLOW CAUSES WINTRY MIX MONDAY AND TUESDAY. && .NEAR TERM /THROUGH SUNDAY/... LINGERING STRATOCUMULUS SHOULD DISSOLVE OVERNIGHT. WITH DIMINISHING WINDS...STILL LIKE OUR IDEA OF COLDER THAN GUIDANCE MINIMUM TEMPERATURES...SINCE ANY MID CLOUDS SHOULD HOLD OFF TILL DAWN IN THE SOUTH. HAVE CLOUDS THICKENING AND LOWERING SUNDAY MORNING...ASSOCIATED WITH THE STRONG WARM AIR ADVECTION. HOWEVER...MOISTURE SOURCE IS LIMITED WITH PRECIPITABLE WATER ONLY AROUND 0.5. SO ALSO KEPT TEMPERATURES DOWN WHERE POPS INCREASE. STILL TOUGH ON WHEN FLAKES WILL REACH THE GROUND AFTER BEING ALOFT FOR SEVERAL HOURS. HAVE SOME LKLY POPS REACHING NE KY AROUND 20 TO 21Z AND SPREADING TOWARD SOUTHERN MOUNTAINS AND BKW BY 22Z. STILL HOLDING CHANCE POPS OFF FOR NORTHERN COUNTIES UNTIL AFTER 21Z. ANY ACCUMULATIONS IN OUR EXTREME WEST AND SOUTH AN INCH OR LESS BY 23Z. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... COMPLEX SYSTEM THIS PERIOD LOOKS JUST A LITTLE COLDER. THE LOWLANDS LOOK TO GET MOST OF THEIR SNOW FROM WARM ADVECTION SUN NT INTO MON WITH HIGH END ADVISORY AMOUNTS POSSIBLE. THE NRN MOUNTAINS ALSO RECEIVE A POUNDING MON NT WHICH WOULD WARRANT WARNINGS IF CURRENT MODEL OUTPUT HOLDS UP. THE CENTRAL AND SRN MOUNTAINS COULD GET ADVISORY CRITERIA ICE AMOUNTS. GIVEN DIFFERENCES AMONG THE MODELS AND FROM RUN TO RUN...IT WAS AGREED AMONG NEIGHBORING OFFICES TO HOLD OFF ON CODING THIS UP AT THIS POINT...ESPECIALLY WITH ONGOING ADVISORIES IN THE NEAR TERM. WILL UPDATE THE HWO TO BETTER REFLECT THESE POSSIBILITIES. THE HIGH PRESSURE SYSTEM REPRESENTING THE CENTER OF THE ARCTIC AIR MASS OVERTAKING THE AREA AT THIS TIME...WILL EXIT THE AREA ON SUNDAY...AND A WARM ADVECTION / OVERRUNNING PATTERN SETS UP LATE SUNDAY THROUGH MON...IN DEEP LAYER S TO SW FLOW VEERING WITH HEIGHT...AHEAD OF UPPER LEVEL S/W TROUGHS APPROACHING FROM THE W. THE FIRST ONE MOVES THROUGH THE GREAT LAKES AND UPPER OHIO VALLEYS SUN NT...WITH INCREASING MOISTURE...CLOUD AND PRECIPITATION OVERRUNNING THE AREA AS A RESULT. WITH THE ANTECEDENT ARCTIC AIR...THE COLUMN REMAINS PROGGED TO REMAIN COLD ENOUGH FOR SNOW THROUGHOUT THE AREA SUN NT...LEADING TO INITIAL ACCUMULATIONS OF GENERALLY 1 TO 3 INCHES LATE SUN AFTERNOON THROUGH SUN NT...THE HIGHEST AMOUNTS S. ONGOING WARM ADVECTION MON EVENTUALLY BRINGS THE COLUMN ABOVE FREEZING FROM H85 DOWN SOMETIME MON AFTERNOON THROUGHOUT MUCH OF THE LOWLANDS. THIS LIMITS SNOWFALL ACCUMULATIONS TO AN INCH OR LESS ACROSS THE LOWLANDS...WHILE ANOTHER 1 TO 3 INCHES ARE POSSIBLE OVER THE NRN MOUNTAINS. A COLD LAYER IS PROGGED TO LINGER BETWEEN H85 AND THE SFC FOR A TIME MON...LEADING TO A PERIOD OF SLEET AND / OR FREEZING RAIN IN THE TRANSITION. THE SECOND S/W TROUGH TRACKS FARTHER S THAN THE FIRST...AS A L/W TROUGH OVER THE ERN U.S BECOMES REESTABLISHED. ONE DIFFERENCE FROM PREVIOUS RUNS IS THAT SFC LOW PRESSURE CENTER GENERATED BY THIS S/W APPEARS TO BE MORE OF A FLAT WAVE AND FARTHER S. AMIDST THE ESTABLISHMENT OF THE L/W TROUGH IN THE E...THIS AMOUNTS TO A COLDER SOLN COMPARED WITH PREVIOUS RUNS...A TREND THAT MAY BE INTERESTING TO FOLLOW. THE S/W APPROACHES MON AND CROSSES MON NT...AS THE SFC WAVE RIDES NEWD JUST E OF THE CENTRAL APPALACHIANS MON NT. ONE LIMITING FACTOR IN A TRANSITION BACK TO SNOW ACROSS THE LOWLANDS MON NT IS THE LACK OF FRESH COLD AIR ARRIVING BEHIND THE SYSTEM. HOWEVER...IT MAY NOT TAKE TOO MUCH FURTHER A TREND TOWARD COLDER TO IMPACT THE PRECIPITATION TYPE FCST FOR MON NT GIVEN THE MARGINAL NATURE OF THE COLUMN TEMPERATURES CURRENTLY PROGGED. AS IS...THE TRACK OF THE SYSTEM AND THE RETURN OF THE COLD AIR ALOFT COULD RESULT IN THE HIGHER ELEVATIONS IN THE MOUNTAINS OF NRN WV GETTING CLOCKED WITH SIGNIFICANT SNOWFALL MON NT. ANOTHER FACTOR IN THIS COMPLEX EVENT IS THE COLD AIR DAMMING IN THE TYPICAL E OF THE MOUNTAINS WEDGE AREA...WHICH COULD RESULT IN AT LEAST ADVISORY CRITERIA ICE ACROSS THE CENTRAL AND SRN MOUNTAINS OF WV AND DOWN INTO SW VA...MAINLY THE ERN SLOPES OR ERN PORTIONS OF THE ERN FLANK COUNTIES OF THE FCST AREA. THE PRECIPITATION WINDS DOWN LATE MON NT INTO TUE AS THE SYSTEM PULLS OUT...ENDING AS RAIN OR DRIZZLE ACROSS THE LOWLANDS TUE AS WE LOSE THE UPPER LEVEL MOISTURE AND WITH IT THE CRYSTAL GROWTH ZONE. USED A NAM AND CONSENSUS BLEND FOR SFC TEMPERATURES AND THE NAM FOR TEMPERATURES ALOFT...AND A NAM/GFS/ECMWF/WPC BLEND FOR QPF. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... BEHIND THE DEPARTING LOW...ANOTHER CLIPPER TYPE SYSTEM EXPECTED TO IMPACT THE AREA...BRINGING A REINFORCING SHOT OF COOL AIR...AND CREATING LIGHT SNOW SHOWERS LATE TUESDAY NIGHT INTO WEDNESDAY. THERE ARE DIFFERENCES BETWEEN THE MODELS WITH THIS SYSTEM...WITH GFS AND NAM INDICATING A STRONGER SYSTEM THAN THE ECMWF. GENERALLY FIGURING AN INCH OR LESS ACROSS THE LOWLANDS...WITH 1 TO 3 ACROSS THE HIGHER TERRAIN. SOME LIGHT SNOW SHOWERS ARE STILL POSSIBLE THROUGH WEDNESDAY EVENING IN THE NORTHWESTERLY FLOW BEHIND THE DEPARTING SYSTEM. DRIER...AND GRADUALLY WARMING WEATHER EXPECTED BEHIND THE CLIPPER...WITH ANOTHER SYSTEM POSSIBLE LATE IN THE WEEK. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... SCATTERED TO BROKEN STRATOCUMULUS AT 2 TO 4 THSD FT AGL. VSBY OCCASIONALLY AROUND 3 TO 5 MILES OVER MOUNTAINS THRU 21Z IN LINGERING SNOW SHOWERS. WINDS DIMINISHING 21Z TODAY THROUGH 02Z SUNDAY. STRATOCUMULUS DISSIPATING OVERNIGHT. SOME SMOKE FROM WOOD BURNING POSSIBLE IN SHALLOW INVERSION IN MOUNTAIN VALLEYS INCLUDING ELKINS TOWARD DAWN SUNDAY. CLOUDS THICKENING AND LOWERING FROM WSW TO ENE ON SUNDAY...BUT STILL AOA 10 THSD UNI-CKB-EKN CORRIDOR THRU 18Z. BY 18Z...SOME LIGHT SNOW MAY START REACHING THE GROUND ALONG WEST VIRGINIA AND KENTUCKY...PLUS ALONG THE KENTUCKY AND VIRGINIA BORDER. CEILINGS 2 TO 4 THSD FT AND VSBY NEAR 3 MILES BY 18Z IN THE EXTREME SOUTHWEST AS SNOW BEGINS. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SUNDAY... FORECAST CONFIDENCE: MEDIUM ALTERNATE SCENARIOS: SNOW MAY REMAIN ALOFT AND NOT REACH THE GROUND THRU 18Z IN SOUTHERN COUNTIES. 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 18 19 20 21 22 23 00 01 02 03 04 05 EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H M M H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY M M M M H H H H H H H H EKN CONSISTENCY L L M M M M M M M M M M PKB CONSISTENCY H H H H H H H H H H H M CKB CONSISTENCY M M M M M M M M M M M M AFTER 18Z SUNDAY... IFR CONDITIONS POSSIBLE IN LIGHT SNOW SUNDAY NIGHT AND MONDAY...TRANSITIONING TO A MIXED PRECIPITATION EVENT FOR MONDAY INTO TUESDAY. WESTERN SLOPES MAY IMPROVE FOR A TIME MONDAY. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...WIND CHILL ADVISORY UNTIL 9 AM EST SUNDAY FOR WVZ032-035>040- 046-047. WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH TUESDAY MORNING FOR WVZ035>038-046-047. WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY AFTERNOON FOR WVZ033-034. OH...NONE. KY...NONE. VA...WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY AFTERNOON FOR VAZ003-004. && $$ SYNOPSIS...KTB/JW/SL NEAR TERM...KTB SHORT TERM...TRM LONG TERM...SL AVIATION...KTB

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