167 FXUS61 KRLX 202036 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 436 PM EDT THU MAR 20 2014 .SYNOPSIS... WARM FRONT TONIGHT INTO EARLY FRIDAY. WEAK COLD FRONT SATURDAY. DISTURBANCE ALOFT PASSES SUNDAY. TURNING COLDER SUNDAY NIGHT AND MONDAY. LOW PRESSURE PASSES SOUTH OF THE AREA TUESDAY. && .NEAR TERM /THROUGH FRIDAY/... MODELS IN VERY GOOD AGREEMENT ON THE MASS AND QPF FIELDS WITH WEAK COLD FRONT THAT DROPS INTO SOUTHEAST OHIO AND NORTHERN WEST VIRGINIA EARLY TONIGHT AND STALLS...BEFORE LIFTING BACK NORTH AS A WARM FRONT FRIDAY MORNING. A RATHER DECENT NORTH TO SOUTH TEMPERATURES GRADIENT SETS UP ACROSS THIS FRONT AROUND 925 MB...WITH THE NAM MORE AGGRESSIVE THAN THE OTHER MODELS...INCLUDING THE GFS...IN SHOWING A COLDER GRADIENT. THIS PLAYS AN IMPORTANT ROLE WITH THE TYPE OF PRECIP THAT WOULD OCCUR IF IT DOES PRECIP TO THE NORTH OF THIS FRONT LATER TONIGHT AND EARLY FRIDAY. WITH AN UPPER DISTURBANCE RIDING EAST SOUTHEAST ALONG THE FRONTAL BOUNDARY LATER TONIGHT...MODELS DO SQUEEZE OUT SOME VERY LIGHT QPF WITH THE FRONT...BUT THE POPS ARE ON THE LOW SIDE. FOR NOW WILL DOWNPLAY THE IMPORTANCE OF THIS FEATURE WITH LOWER POPS. WILL GO WITH THE GFS FOR DETAILS WHICH MEANS GONG WITH A SLIGHTLY WARMER SCENARIO TONIGHT...BUT STILL COLD ENOUGH FOR ANY VERY LIGHT WINTRY MIX THAT WOULD OCCUR ACROSS OUR NORTHERN BORDER. IN ANY CASE...WITH SURFACE TEMPERATURES MARGINAL... WARM GROUND...AND VERY LIGHT QPF IF IT DOES OCCUR...WOULD NOT EXPECT A HAZARD HEADLINE FOR THIS. THE FRONT LIFTS BACK NORTH FRIDAY MORNING WITH ANY PRECIP IN THE FAR NORTH ENDING AS LIGHT RAIN AROUND MID MORNING. SOUTHERLY WINDS INCREASE IN THE WARM SECTOR FOR FRIDAY AFTERNOON. DEWPOINTS WILL BE SLOW TI INCREASE...AND WITH ONE MORE DAY OF DRYING...WE HAVE TO KEEP AN EYE OUT ON FIRE DANGER FRIDAY AFTERNOON...ESPECIALLY IN THE WEST. RIGHT NOW...THINK A POSSIBLE SPS AT BEST IN THE WEST. FOR TEMPERATURES...LEANING TOWARD THE MAV GUIDANCE. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... MAIN CHALLENGE IN OUR DETAILED DETERMINISTIC WEATHER GRIDS IS DAY 3/SUNDAY. CONSENSUS WITH SURROUNDING NWS OFFICES AND WPC IS THAT NAM SOLUTIONS HAVE BEEN TOO AGGRESSIVE. THE NAM SOLUTION HAS NICE MID LEVEL FORCING FROM COUPLED 250 MB JET MAXIMUMS. THOUGH THINKING THE ECMWF MAY BE TOO FAR SOUTH. WE TRENDED FURTHER NORTH WITH THE PRECIPITATION...SO INCREASED POPS FURTHER NORTH. IN ANY CASE THE MAIN FORCING SHOULD BE OF RELATIVELY SHORT DURATION MOSTLY AROUND 6 HOURS. SO SYSTEM SHOULD BE EXITING IN EASTERN COUNTIES LATE IN THE DAY. KEPT TEMPERATURES COOLER THAN MOST MOS GUIDANCE FOR SUNDAY. WITH COOLING ALOFT...WILL ALSO KEEP THE POSSIBILITY OF WET SNOW UP THROUGH AROUND 40 DEGREES. WILL UPDATE THE HAZARDOUS WEATHER POTENTIAL TO NOT RULE OUT SOME WINTER WEATHER ADVISORIES OVER THE CENTRAL AND SOUTHERN MOUNTAIN COUNTIES FOR SUNDAY IF SYSTEM IS STRONGER. OTHERWISE...MAIN ADJUSTMENT TO OUR FORECAST IN FRIDAY NIGHT INTO SATURDAY TIME FRAME WAS TO SLOW DOWN THE FRONT 1 TO 2 HOURS FOR SOME LIGHT RAIN SHOWERS. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... L/W TROUGH SETTLES INTO THE EASTERN CONUS AT THE BEGINNING OF THE PERIOD...AND THEN FLATTENS OUT CONSIDERABLY TOWARD THE END OF THE PERIOD AND WORK WEEK. CONUNDRUM EARLY ON WITH EXITING SOUTHERN STREAM SYSTEM...WHICH CANNOT EXIT IF IT DOES NOT AFFECT THE AREA IN THE FIRST PLACE. THE NAM12 CONTINUES TO BE MOST BULLISH ON THIS SYSTEM AND STRONGLY SUGGESTS PRECIPITATION IS STILL HANGING ON ACROSS EASTERN PORTIONS OF THE FCST AREA AS SUN NT BEGINS. THE GFS AFFECTS MUCH OF THE AREA WITH THIS SYSTEM SUN...THE CANADIAN AND ECMWF CONTINUE TO SHUNT THE SYSTEM TO THE S...HAVING IT GRAZE SOUTHERN AND EASTERN PORTIONS OF THE FCST AREA. THE KEY IS THE NORTHERN STREAM S/W CROSSING THE OHIO VALLEY. THE NAM12 IS SLOWEST WITH THIS FEATURE...HAVING IT BACK OVER IN AT 00Z MON...THE OTHER MODELS HAVING IT OVER OHIO...EVEN THE THE OH/PA LINE BY THEN IN THE CASE OF THE ECMWF. LEFT A SCHC FOR WET SNOW EXTREME E EARLY ON...WHICH THEN GOES AWAY QUICKLY SUN EVE. AFTER HIGH PRESSURE GIVES RISE TO A DRY...CHILLY DAY ON MON...THE NEXT FEATURE ROLLS THROUGH LATE MON NT THROUGH TUE...AS S/W TROUGHS IN THE SOUTHERN AND MIDDLE STREAMS DIG SEWD THROUGH THE OHIO AND TN VALLEYS...INTERACTING TO CARVE OUT THE DEEPENING L/W TROUGH OVER THE EASTERN CONUS. MODELS SHOW RAPIDLY DEEPENING LOW PRESSURE MOVING NEWD OFF THE E COAST TUE AND TUE NT...BUT ALL TRACK THE LOW FAR ENOUGH E TO MITIGATE ITS EFFECTS IN AND ESPECIALLY W OF THE APPALACHIANS. THE CHANCE FOR WET SNOW SNOW TUE IS HIGHEST IN THE E AND ATTRIBUTABLE MAINLY TO COLD ADVECTION UPSLOPE FLOW...AND THE TRAILING NORTHERN STREAM S/W TROUGH...THE OUT AHEAD SOUTHERN STREAM FEATURE CONNECTED TO THE SFC SYSTEM. ARCTIC HIGH PRESSURE DRIFTS BY MIDWEEK...FOLLOWED BY MODERATING TEMPERATURES IN THE S FLOW ON THE BACK SIDE OF THE EXITING HIGH...AND BENEATH RISING HTS ALOFT...DAY 7. ASIDE FROM DAY 7...STAYED ON LOW END OF GUIDANCE FOR HIGHS INCLUDING LOWER THAN PREV ON TUE...NO MAJOR CHANGES ON LOWS. EMPLOYED SOME BIAS CORRECTED VERSIONS OF CONSENSUS MOS AND ECMWFHIRES AS WELL AS SOME WPC WITH NO MAJOR DEVIATIONS FROM THE LATTER. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... 18Z THURSDAY THRU 18Z FRIDAY... WEAK FRONT WILL DROP SOUTH INTO NORTHERN ZONES AND STALL OVERNIGHT...BEFORE LIFTING BACK NORTH ON FRIDAY. VFR SCT-BKN CU FIELD DISSIPATING BY 21Z. MID CLOUDS INCREASE FROM THE NORTHWEST AHEAD OF AN UPPER LEVEL DISTURBANCE RIDING ALONG ALONG THE FRONT. GUSTY WEST WINDS DIMINISH QUICKLY BY 00Z. AFTER 05Z...NORTHERN THIRD OF AREA...BECOMING VFR CEILINGS 3500-5000 FEET WITH A SCATTERED WINTRY MIX. ELSEWHERE...SCT-BKN 5000-7000 FEET AGL. AFTER 12Z...VFR SCT CU FIELD CENTRAL AND SOUTH. NORTHERN THIRD OF AREA...IMPROVING TO VFR SCT-BKN 5000 FEET AGL BY 17Z. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY... FORECAST CONFIDENCE: HIGH...EXCEPT MEDIUM NORTH THIRD OF AREA. ALTERNATE SCENARIOS: CEILINGS COULD OCCASIONALLY DIP INTO IFR IN PRECIP NORTH THIRD OF AREA LATER TONIGHT AND EARLY FRIDAY. 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 EDT 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 CRW CONSISTENCY H H H 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 H H H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H H H H H H H AFTER 18Z FRIDAY... NO WIDESPREAD IFR EXPECTED. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...KTB/TRM/JMV NEAR TERM...JMV SHORT TERM...KTB LONG TERM...TRM AVIATION...JMV