000 FXUS61 KRLX 210821 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 350 AM EDT TUE APR 21 2009 .SYNOPSIS... TODAY THROUGH WEDNESDAY WILL FEATURE MULTIPLE DISTURBANCES WITHIN A COOL MOIST AND UNSTABLE AIR MASS. HIGH PRESSURE WITH DRY WEATHER AND A WARMING TREND THURSDAY THROUGH THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... MODELS IN VERY GOOD AGREEMENT ON LIFTING A WELL DEFINED SHORT WAVE...AND MOVING ITS ASSOCIATED COLD FRONT...ACROSS OUR AREA LATER THIS MORNING AND EARLY AFTERNOON...BEFORE THE COLD UPPER TROUGH WITH ITS DEEP WRAPAROUND MOISTURE MOVES IN FROM THE WEST LATE THIS AFTERNOON AND THIS EVENING. WHILE MOISTURE IS NOT THAT IMPRESSIVE...DYNAMICS ARE STRONG ENOUGH TO SQUEEZE OUT AN ORGANIZED BAND OF SHOWERS WITH THIS FEATURE. ISOLATED THUNDERSTORMS ARE POSSIBLE....ESPECIALLY IN THE EAST THIS AFTERNOON IF WE CAN GENERATE SOME CAPE WITH ANY HEATING. THIS BAND OF SHOWERS WILL EXIT THE WEST THIS MORNING...AND THE MOUNTAINS BY LATER AFTERNOON. THERE WILL BE A RELATIVE MIN OF POPS BEHIND THE FRONT THIS AFTERNOON AND EARLY EVENING BEFORE SHOWERS RETURN TONIGHT IN THE WRAPAROUND FLOW. WITH COLD AIR MOVING IN ALOFT...EXPECT A CHANGEOVER TO SNOW SHOWERS MOSTLY ABOVE 2500 FEET. NO WELL DEFINED FEATURES SEEN ROTATING THRU THE UPPER TROUGH TONIGHT...BUT MODELS HIGH ON POPS. HOWEVER...SHOWERS WILL BE LIGHT GIVEN THE HIGHER PWS WILL BE KICKED OUT WITH THE SHORT WAVE TODAY. SHOWERS WILL TEND TO CONCENTRATE MORE IN UPSLOPE AREAS AS THE NIGHT WEARS ON...BUT EVEN THERE MORE OF A WESTERLY WIND COMPONENT WILL KEEP AMOUNTS LIGHT THERE. STILL...MAYBE AROUND AN INCH OF SNOW ON THE RIDGETOPS BEFORE THE NIGHT IS OVER. FOR TEMPERATURES...AM GOING ABOVE GUIDANCE TODAY SINCE THERE WILL PROBABLY BE MORE BREAKS IN THE CLOUDS THAN MODELS DEPICT BEHIND THE FRONT...AND THE REAL GOOD COLD ADVECTION HOLDS OFF TIL AFTER PEAK HEATING. FOR TONIGHT...GOING ON THE COLDER SIDE OF GUIDANCE IN HIGHER ELEVATIONS...AND ON THE MILDER SIDE OF GUIDANCE IN THE LOWLANDS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... AXIS OF 500MB TROUGH IS SITTING OVER THE CWA AT THE VERY START OF THE PERIOD. ALL MODELS HAVE NOW COME INTO AGREEMENT ON A FINAL SOLID SHORTWAVE PASSING THROUGH THE BACK OF THE TROUGH AS IT STARTS TO LIFT OUT WEDNESDAY. WITH COLD CORE ALOFT...1000-500MB THICKNESSES ONLY IN THE LOWER 530S DECAMETER RANGE...ATMOSPHERE LOOKS TO GET RATHER UNSTABLE. THE SHORTWAVE GOES THROUGH DURING A DIURNALLY FAVORABLE TIME OF DAY FOR CONVECTION. IN ADDITION TO THE INCREASED POPS FOR THE STRONG SHORTWAVE /LIKELY TO CATEGORICAL FOR NORTHERN AND EASTERN ZONES/...I ALSO ADDED CHANCE OF THUNDER FOR MUCH OF THE AREA. WITH FREEZING LEVEL SO LOW...SMALL HAIL WILL BE POSSIBLE EVEN IN THE SHOWERS WITHOUT THUNDER. IT WILL ALSO BE QUITE BREEZY...WITH THE GOOD MIXING AND 850MB WINDS AT 30-40 KNOTS. SOME SNOW IS STILL EXPECTED FOR THE RIDGES GENERALLY ABOVE 3000 FT ELEVATION WEDNESDAY MORNING...AND AGAIN LINGERING WEDNESDAY NIGHT...BUT WARM GROUND AND LIMITED COOLING OF THE BOUNDARY LAYER WILL KEEP ANY ACCUMULATIONS LIGHT. HIGH PRESSURE ARRIVES THURSDAY TO MARK TRANSITION TO A DRY WARMING PATTERN. WITH CLEARING OCCURRING IN THE LOWLANDS DURING PREDAWN HOURS THURSDAY MORNING...WILL HAVE POSSIBILITY OF FROST...ESPECIALLY NORTH OF I-64. IN A PATTERN MORE TYPICAL OF SUMMER...BERMUDA HIGH SETS UP TO OUR SOUTHEAST...PLACING US IN A SOUTHWEST FLOW WITH RISING THICKNESSES AND A CORRESPONDING TEMPERATURE TREND TO ABOVE NORMAL FROM FRIDAY ONWARD. MODELS ARE STARTING TO INDICATE WEAK WAVES WITHIN THAT SOUTHWEST RETURN FLOW...INCLUDING ONE LATE THURSDAY NIGHT INTO FRIDAY MORNING WHICH MAY PRODUCE MORE CLOUDS THAN PREVIOUSLY THOUGHT. AT THIS TIME THOUGH...NOT EXPECTING ANY PRECIPITATION. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... SPRING FINALLY ARRIVES IN FULL FORCE IN THE EXTENDED RANGE AS ALL MODELS SHOW THAT THE SOUTHEASTERN US RIDGE WILL SET UP AND TAKE HOLD OF THE REGION. THE GFS CONTINUES TO HAVE SOME TROUBLE WITH THE RUN TO RUN CONSISTENCY AS IT TRIES TO PERIODICALLY KNOCK DOWN THE RIDGE AND TRY TO GET A NRN STREAM COLD FRONT TO SLIDE INTO THE OHIO VALLEY...AT DIFFERENT TIMES BETWEEN SAT NIGHT AND MONDAY. BUT THE ECMWF AND CANADIAN BOTH SHOW THAT THE RIDGE IS VERY STRONG AND KEEPS THE FRONT NORTH OF THE AREA. CLIMATOLOGICALLY...THE RIDGE TENDS TO HOLD ON VERY STRONG SO EXPECT THAT THE GFS ATTEMPTS TO MOVE THE FRONT ARE UNLIKELY TO HAPPEN...ESPECIALLY CONSIDERING THE OTHER GUIDANCE. SO WITH THAT SAID...HAVE KEPT THE FORECAST DRY FRIDAY THROUGH MONDAY AND KEPT THE SKY COVER DOWN...ALLOWING FOR LOTS OF SUNSHINE. FOR TEMPERATURES...SHOULD SEE A GOOD WARM UP...AS 850 MB TEMPS CLIMB INTO THE 14C TO 16C RANGE WITH THE WSW FLOW ALOFT. WITH FULL MIXING THESE TYPES OF VALUES SHOULD PUSH THE TEMPERATURES INTO THE UPPER 70S TO THE MID 80S. AS A RESULT HAVE FOLLOWED CLOSER TO THE HPC GUIDANCE...WHILE THE MEX NUMBERS LOOK TOO COOL ON DAYS 6 AND 7. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... 06Z TUESDAY THRU 06Z WEDNESDAY... A COLD FRONT WILL MOVE ACROSS THE AREA THIS MORNING AND EARLY AFTERNOON...WITH A BAND OF SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM. OUTSIDE OF MVFR CONDITIONS IN SHOWERS...EXPECT VFR CEILINGS THROUGH 00Z...AND GUSTY WEST WINDS THIS AFTERNOON BEHIND THE FRONT. MVFR CEILINGS WILL RUSH BACK IN FROM WEST TO EAST AFTER 00Z...ALONG WITH LIGHT RAIN SHOWERS...BECOMING IFR IN SNOW SHOWERS ABOVE 2500 FEET AFTER 03Z. AVIATION OUTLOOK /BEYOND 06Z WEDNESDAY/... POSSIBLE IFR MAINLY FOR HIGHER ELEVATION TERMINALS. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...JMV NEAR TERM...JMV SHORT TERM...MDP LONG TERM...ESS AVIATION...JMV