149 FXUS61 KRLX 021747 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 1245 PM EST FRI MAR 2 2012 .SYNOPSIS... WARM FRONT TODAY. COLD FRONT TONIGHT. SHOWERS AND THUNDERSTORMS WITH EACH. COLD WEATHER ESTABLISHES FOR THE WEEKEND INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... 930 AM UPDATE... BUMPED UP THE SPEED JUST A LITTLE FOR INCOMING POPS BASED ON CURRENT RADAR TRENDS. SHOWERS AND STORMS ARE SLOWLY DIMINISHING IN INTENSITY AND COVERAGE AS THEY MOVE THROUGH WESTERN KY AND INTO WV. IT IS LIKELY THEY ARE OUTRUNNING THE BEST LOW LEVEL MOISTURE AHEAD OF THE WARM FRONT. AS THE WARM FRONT CONTINUES TO LIFT...THESE SHOWERS AND THUNDERSTORMS SHOULD PROGRESS FARTHER INTO WV AND SOUTHEAST OHIO. THOUGHTS POPS LOOKED PRETTY GOOD FROM LATE AFTERNOON THROUGH TONIGHT...WITH MAIN EVENT THIS EVENING INTO TONIGHT AHEAD OF AND ALONG A COLD FRONT. MODELS STILL SHOWING UP TO ABOUT 1000 J/KG CAPE INTO EASTERN KY...WITH PLENTY OF SHEAR EVERYWHERE. GOOD CHANCE OF THUNDERSTORMS WITH SOME OF THEM STRONG TO SEVERE. THE PRIMARY SEVERE THREAT FOR OUR CWA WILL BE DAMAGING WIND AND HAIL...BUT WITH SUCH A HIGH SHEAR ENVIRONMENT...AND HIGH CHANCE OF STRONG SUPERCELLS TO OUR WEST...CANNOT RULE OUT TORNADOES EITHER. PREVIOUS DISCUSSION... AS MODELS HAVE SUGGESTED...FIRST CONVECTION GETTING STARTED WITH THE WARM ADVECTION/WARM FRONT OVER THE SOUTHERN TENNESSEE BORDER AND SOUTHERN APPALACHIA. SIGNIFICANT CHANGE IN AIRMASS EXPECTED TODAY WITH THE PASSAGE OF THE WARM FRONT. WILL EXPECT INCREASES IN SURFACE AND LOW LEVEL MOISTURE...WHICH WILL HELP SET THE STAGE FOR A POTENT DAY WEATHER WISE ACROSS OUR CWA. FIRST BATTLE IS THE POTENTIAL FOR THUNDER WITH THE DEEPENING MOISTURE WITH THE WARM FRONT. NEED TO LOOK ABOVE 900MB/INVERSION LAYER WITH THIS ASSESSMENT...AND ALSO TAKE INTO ACCOUNT THE SPEED AND DIRECTIONAL SHEAR AS THE LOW LEVEL DYNAMICS INCREASE ON THE WHOLE WITH WARM FRONTAL PASSAGE. THAT BEING SAID...WHILE THUNDER IS EXPECTED...FEEL THE COVERAGE WILL BE MORE SCATTERED LATER THIS MORNING AND EARLY AFTERNOON IN THIS TYPE OF REGIME. ONCE IN THE WARM SECTOR THIS AFTERNOON AND EVENING...DROP THE POPS DOWN TO CHANCE WITH THE THOUGHT THAT SHOWER AND THUNDERSTORM COVERAGE SHOULD BE SIGNIFICANTLY LESS WELL AHEAD OF THE COLD FRONT. CONCERNS TURN TO THE WEST SOUTHWEST AT THIS POINT WHERE SEVERE WEATHER WILL LIKELY HAVE BEEN ONGOING...AND FAST MOVING CELLS AND QLCS FEATURES WILL TREK TOWARDS OUR AREA. BEST LAPSE RATES WILL BE WEST OF HERE DURING THE PRIME HEATING HOURS TODAY AS OPPOSED TO OUR CWA...BUT IT IS IMPORTANT TO NOTE THAT SPC HAS EXPANDED THE MODERATE RISK FURTHER EAST TOWARDS THE CHARLESTON AREA...AND WILL SEE SPILL OVER FROM ACTION FROM AREAS TO THE WEST SOUTHWEST INTO OUR NECK OF THE WOODS. NAM BRINGS SURFACE BASED CAPE VALUES OVER 1000J/KG TO THE MIDDLE OHIO VALLEY AND CENTRAL APPALACHIANS...BUT THIS CAN BE OVERDONE AT TIMES WITH SURFACE DEWPOINT BIASES FROM THAT MODEL. WITH SUNSET...WILL BE LOSING THE INSTABILITY OFF THE SURFACE AND WILL NOT HAVE THE SAME HIGH LAPSE RATES AS MENTIONED FOR THE LOWER OHIO AND TENNESSEE VALLEYS. SO...WITH THE COLD FRONT NOT SLATED TO COME THROUGH UNTIL LATE THIS EVENING AND INTO TONIGHT...THIS COULD HELP CURB SOME THE STRENGTH OF STORMS ASSOCIATED WITH THE FRONT ITSELF. IT IS QUITE POSSIBLE THAT WE WILL HAVE DEALT WITH SIGNIFICANT NUMBERS OF STORMS BY THIS POINT HOWEVER...AND THE COLD FRONT WILL LIKELY NOT BE OUR ONLY PROBLEM TODAY/TONIGHT. FLASH FLOOD GUIDANCE IS FAIRLY LOW ACROSS MUCH OF THE CWA IN BOTH THE ONE HOUR AND THREE HOUR RANGES...THANKS TO THE ACTIVITY FROM WEDNESDAY. WHITE NOT IN ANY EXCESSIVE RAINFALL GRAPHICS FROM HPC...NO VEGETATION THIS TIME OF YEAR MAKES FOR MORE OF THE BURDEN OF RAINFALL TO BE ABSORBED BY THE STREAMS...CREEKS AND RIVERS. WARM ADVECTION RAINFALL WILL DICTATE NEEDS TODAY AS FAR AS WATCHES. RFC QPF AMOUNTS AT THIS TIME ARE GENERALLY A BIT LOWER COMPARED TO THOSE FROM WEDNESDAY. ALSO LOWER COMPARED TO THE ATMOSPHERIC SET UP WEDNESDAY IS THE PRECIPITABLE WATER VALUES WHICH PEAK AT AROUND THE 1.15 INCH RANGE. LAST BUT NOT LEAST...WARM SECTOR AIRMASS SHOULD GIVE WELL ABOVE NORMAL TEMPERATURES TODAY APPROACHING 70F OVER THE LOWLANDS...ALTHOUGH DO NOT THINK THERE WILL BE MANY...IF ANY...LOCATIONS TOPPING THIS MARK. EXPECTING WINDS TO PICK UP TODAY AS WELL...WITH GUSTS OVER 20KTS LATER THIS AFTERNOON AND INTO TONIGHT. && .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... AMPLIFYING UPPER TROUGH OVER THE OHIO VALLEY BRINGS MUCH COLDER AIR IN THIS PERIOD...ESPECIALLY BEGINNING SUNDAY WITH A REINFORCING SURGE OF COLD AIR AND DEEPER MOISTURE UNDER AN AMPLIFYING UPPER TROUGH. AHEAD OF THIS COLDER SURGE...SATURDAY LOOKS TO BE A MOSTLY DRY AND SEASONABLE DAY...WITH A RELATIVE DRY SLOT IN SOUTHWEST FLOW UNDER A COOLING ATMOSPHERE ALOFT. THIS WILL BRING A RATHER BLUSTERY SATURDAY ONCE MIXING DEVELOPS...DIMINISHING AT NIGHT WITH LOSS OF HEATING. BACK TO SUNDAY...COLD ADVECTION BEGINS IN EARNEST WITH MOSTLY CLOUDY SKIES. INTRODUCED CHANCE POPS LOW LANDS...AND LIKELY POPS IN NORTHERN AND CENTRAL MOUNTAINS WHERE SOME OROGRAPHIC UPSLOPE FLOW WILL ENHANCE SHOWERS. NOT IDEAL UPSLOPE COMPONENT...BUT MOISTURE UP THROUGH 700 MB IS NOTED. IN A NUTSHELL...NOTHING HEAVY. THIS TIME OF YEAR AND DAYTIME HOURS STRONGLY SUGGEST RAIN SHOWERS...EXCEPT SNOW SHOWERS ABOVE 2000 FEET. MAYBE AN INCH OF SNOW IN THE HIGHER ELEVATIONS. WILL SPLIT THE COLDER MET AND MILDER MAV TEMP GUIDANCE...RANGING FROM NEAR 40 LOW LANDS TO UPPER 20S HIGHER MOUNTAIN ELEVATIONS. MODELS FEATURE AN UPPER DISTURBANCE SWINGING THRU THE AREA SUNDAY NIGHT...BUT TRACK AND SPEED ARE DIFFERENT IN THE MODELS. GIVEN THIS LACK OF CONFIDENCE ON THIS FEATURE THIS FAR OUT...WILL TREAT THIS AS MAINLY AN UPSLOPE EVENT. EXPECT RAIN SHOWERS TO SNOW SHOWERS LOW LANDS WITH PERHAPS A LIGHT COATING IN SPOTS...BUT A FEW INCHES ARE POSSIBLE IN THE HIGHER ELEVATIONS OF THE NORTHERN AND CENTRAL MOUNTAINS. LOWS FROM THE UPPER 20S LOW LANDS TO THE UPPER TEENS HIGHER MOUNTAINS. FOR MONDAY...HIGH PRESSURE BUILDS IN RAPIDLY WITH LINGERING MOUNTAINS SNOW SHOWERS ENDING EARLY AND SUNSHINE INCREASING FROM WEST TO EAST. STILL..EXPECT TEMPERATURES TO BE BELOW NORMAL...IN THE LOWER 40S LOW LANDS. && .LONG TERM /TUESDAY THROUGH THURSDAY/... PRIMARY FORECAST CONCERN WILL BE A CHANCE OF PRECIPITATION SUNDAY NIGHT INTO MONDAY AS A SHORTWAVE TROUGH MOVES BY THE REGION. SUNDAY NIGHT...INITIALLY LARGE SCALE FORCING FOR ASCENT PUSHES EASTWARD OUT OF THE AREA BUT WILL QUICKLY REDEVELOP DURING THE OVERNIGHT HOURS AS A SHORTWAVE MOVES NW-SE THROUGH THE MEAN FLOW AROUND THE UPPER LEVEL TROUGH BASE. THIS FORCING IS MAXIMIZED OVER THE SOUTHERN CWA AROUND 12Z MON BEFORE LARGE SCALE SUBSIDENCE QUICKLY DEVELOPS ACROSS AREA BY 18Z MON IN ITS WAKE...WITH TROUGH AXIS EAST OF AREA BY THEN. IN ADDITION...GOOD PVA AND LOW LEVEL WARM ADVECTION AT BOTH 700MB AND 850MB SHOULD BE ENOUGH TO GENERATE SOME PRECIP OVER THE AREA...WITH HIGHEST POPS ACROSS SOUTHERN AND WESTERN CWA BTWN 06Z-12Z MON. TEMPS WILL DROP INTO THE LOWER 30S MOST LOCATIONS BY 06Z AND WITH MODEL CONSENSUS QPF AROUND THE 0.1 TO 0.2 INCH RANGE...AN INCH OR TWO OF SNOW WILL BE POSSIBLE. PRECIP WILL BY AND LARGE COME TO END BY MIDDAY MONDAY BUT WILL CONTINUE SLIGHT CHANCE/LOW CHANCE POPS MAINLY ACROSS SOUTHERN ZONES AND MOUNTAINS UNTIL 00Z TUE TO ACCOUNT FOR PLENTIFUL LOW LEVEL MOISTURE IN PLACE WITH A 700MB BAROCLINIC ZONE PROGGED NEAR THE WESTERN/SOUTHERN CWA MON AFTERNOON. SNOW WILL CHANGE TO RAIN HOWEVER ACROSS LOWLANDS AS TEMPS WARM THROUGH THE 30S INTO THE 40S. ALL PRECIP SHOULD END BY TUE 00Z WITH CLEARING SKIES. TUE MORNING WILL BE COLDEST MORNING DURING THE PERIOD. WITH 925MB TEMPS AROUND -3C TO -4C 12Z TUE AND MOSTLY CLEAR SKIES/LIGHT WINDS...HAVE CONTINUED TO LOWER MINS A FEW DEGREES DOWN INTO THE LOW 20S ACROSS THE LOWLANDS. HIGHS TUE WILL WARM TO NEAR SEASONAL LEVELS AND INTO THE 60S WED/THU AS UPPER LEVEL RIDGING BUILDS INTO THE REGION. && .AVIATION /18Z FRIDAY THROUGH TUESDAY/... SHOWERS AND THUNDERSTORMS ONGOING ACROSS FORECAST AREA. THESE ARE STILL AHEAD OF THE WARM FRONT...SO EXPECT AT LEAST SCATTERED ACTIVITY TO CONTINUE AS THE WARM FRONT MOVES THROUGH AND THE WARM SECTOR TAKES OVER. TRIED TO TIME OUT A BRIEF BREAK...OR AT LEAST A REDUCTION IN PRECIP COVERAGE BETWEEN THE WARM FRONT ACTIVITY THIS AFTERNOON AND THEN THE COLD FRONT BASED PRECIP FOR LATER THIS EVENING. WITH THAT SAID...STILL KEPT MAINLY MVFR CONDITIONS THROUGHOUT WITH SCATTERED SHOWERS AND THUNDERSTORMS. WILL HANDLE LOWER CIGS AND VSBYS IN HEAVIER SHOWERS WITH TEMPOS AS NEEDED. AFOREMENTIONED COLD FRONT WILL COME THROUGH LATE THIS EVENING...INTO THE OVERNIGHT...BRINGING INCREASED THUNDERSTORM ACTIVITY...WITH STRONG TO SEVERE STORMS POSSIBLE AHEAD OF THE FRONT. STRONG GUSTY WINDS AND HAIL SHOULD BE THE MAIN THREAT. SHOWERS AND THUNDERSTORMS SHOULD DIMINISH PRETTY RAPIDLY AFTER THE COLD FRONT MOVES THROUGH. AS THE WARM FRONT PASSES TODAY...SYNOPTIC FLOW WILL BECOME GUSTY OUT OF THE SOUTH. THEN AS THE COLD FRONT PASSES ACROSS THE AREA...FROM 03Z TO 07Z...WINDS WILL BEGIN TO TURN TO THE WEST BUT REMAIN ON THE GUSTY SIDE. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SATURDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: UNCERTAINTY REMAINS ON EXACT TIMING AND LOCATIONS OF STRONGEST CONVECTION AND RELATED MVFR AND IFR CONDITIONS. TEMPOS MAY BE NEEDED FOR BRIEF IFR...GUSTY THUNDERSTORM WINDS...AND HEAVY RAIN/THUNDERSTORMS. 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 M L L L H H M M M M M M HTS CONSISTENCY H L L L L L M M M M M M BKW CONSISTENCY H H M L M L L M M M M M EKN CONSISTENCY H H M H H M L M M M M M PKB CONSISTENCY H M L L L L M M M M M M CKB CONSISTENCY H H H M M M H H H M M M AFTER 18Z SATURDAY... MVFR TO IFR POSSIBLE IN MOUNTAIN SNOW SHOWERS SATURDAY AFTERNOON THROUGH SUNDAY. && .HYDROLOGY... GIVEN LOW FFG VALUES AND SEVERAL ROUNDS OF SHOWERS AND HEAVY THUNDERSTORMS...SOME AREA WILL EASILY RECEIVE EXCESSIVE RUNOFF RESULTING IN FLOODING. THE MOST VULNERABLE AREA INCLUDE N CNTRL WV AND A SMALL AREA IN NORTHERN ATHENS AND SOUTHERN WASHINGTON COUNTY...WHERE AS LITTLE AS THREE QUARTERS OF AN INCH WITHIN AN HOUR COULD START CAUSING PROBLEMS. FFA ISSUED FOR ALL BUT EXTREME WESTERN COUNTIES BEGINNING 2 PM THIS AFTERNOON AND RUNNING THROUGH THE OVERNIGHT. THE WESTERN COUNTIES ARE DRIER AND WILL NOT RECEIVE QUITE AS MUCH RAINFALL. OTHERWISE PW VALUES OF 1-1.2 INCHES AND 60 KTS OF LOW LEVEL FEED WILL EASILY SUPPORT RAINFALL AMOUNTS OVER AN INCH...WITH AREA THAT GET HIT HARD MORE THAN ONCE PUSHING TWO INCHES. NO MAJOR MAINSTEM RIVER PROBLEMS ARE EXPECTED AT THIS TIME ALTHOUGH MOST GAGES SHOULD GET AT LEAST AS HIGH AS THEY DID FROM THE LAST EVENT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR WVZ005>011-013>020- 024>040-046-047. OH...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR OHZ067-075-076- 085>087. KY...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR KYZ101>103-105. VA...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR VAZ003-004. && $$ SYNOPSIS...JMV/26 NEAR TERM...MZ/26 SHORT TERM...JMV LONG TERM...GG AVIATION...MZ HYDROLOGY...TRM