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