Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 041305
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
905 AM EDT WED MAY 4 2016

.SYNOPSIS...
COLD FRONT CROSSES WEDNESDAY NIGHT. LARGE UPPER LEVEL LOW BRINGS
COOL AND UNSETTLED WEATHER FOR THURSDAY THROUGH FRIDAY. WARM
FRONT SATURDAY. ANOTHER COLD FRONT SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
830 AM UPDATE. INCREASED POPS THIS MORNING ALONG AND EAST OF A
PKB-CRW LINE. POPS WILL TAPER OFF LATER THIS MORNING FROM
SOUTHWEST TO NORTHEAST AS THE CULPRIT SHORT WAVE LIFTS OUT. BY
LATE MORNING...WILL BE BACK TO ORIGINAL FORECAST WITH
SHOWERS/STORMS COMING IN FROM THEW EST AHEAD OF THE COLD FRONT.


PREVIOUS DISCUSSION...
WEAK SURFACE HIGH SHIFTS EAST THIS AFTERNOON AND FOR THE MOST
PART WINDS WILL BE LIGHT THROUGH THE DAY WITH SOUTHWEST WINDS
PICKING UP SLIGHTLY AHEAD OF AN APPROACHING COLD FRONT LATER IN
THE AFTERNOON AND EARLY EVENING. DECIDED TO KEEP POP CLOSE TO
PREVIOUS FORECAST WITH BULK OF SHOWERS ARRIVING LATE AFTERNOON TO
EARLY EVENING WITH THE COLD FRONT AS NAM/GEM/AND MESO MODELS ARE
ADVERTISING. UPPER LEVEL LOW DIVING SOUTHWARD WILL BRING COLD
TEMPS ALOFT WITH T700 -2 STANDARD DEVIATIONS BELOW NORMAL.
INSTABILITY WILL BE WEAK BUT WITH SUCH LOW FREEZING LEVELS...ANY
STORMS THAT DEVELOP WILL LIKELY BRING SMALL HAIL OR GRAUPEL THIS
AFTERNOON AND EVENING.

THIS SYSTEM DOES NOT ADVERTISE HIGH PWATS WITH IT...SO NOT
EXPECTING TORRENTIAL RAIN. HOWEVER...WE HAVE TO STILL KEEP A CLOSE
EYE ON THE FLASH FLOOD THREAT DUE TO WEAK FLOW ALOFT WITH A UPPER
LEVEL SYSTEM. CORFIDI VECTORS...GENERALLY LESS THAN 10KTS COULD
MAKE FOR NEARLY STATIONARY SHOWERS/STORMS AND TRAINING OR BANDING WILL
BE A REAL POSSIBILITY AS UPPER LOW PIVOTS ACROSS OUR AREA TONIGHT.
THE BEST CHANCE FOR HEAVIER RAINFALL WILL LIKELY BE IN OUR EASTERN
MOUNTAINS...WHERE UPSLOPING COULD ENHANCE RAINFALL TOTALS. OVERALL
QPF SHOULD BE FAIRLY LIGHT IN MOST AREAS...BUT LOCALIZED HEAVY
RAINFALL WILL BE POSSIBLE WITH SLOW MOVING SHOWERS/STORMS AND THIS
COMBINED WITH SATURATED SOILS ALREADY WILL ELEVATE THE THREAT FOR
LOCALIZED FLOODING. AT THIS TIME THOUGH CONFIDENCE IS TOO LOW TO
ISSUE A FLASH FLOOD WATCH AT ANY ONE LOCATION...BUT THE THREAT IS
HIGH ENOUGH THAT IT WARRANTED A SEE TEXT IN WPC EXCESSIVE RAINFALL
OUTLOOK.

TEMPERATURES WILL ALSO CONTINUE ON THE COOL SIDE WITH THE CHILLY
PATTERN AS UPPER LOW MOVES OVERHEAD LATE TONIGHT INTO THURSDAY
MORNING.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
BY 00Z THURSDAY...THE DEEP LOW PRESSURE SYSTEM WILL BEGIN TO EXIT
THE AREA TO THE EAST. BACK AROUND PCPN WILL KEEP POPS GOING ACROSS
THE AREA. THE NAM SHOWS SFC CAPE REACHING 1000 J/KG ON THURSDAY.
THEREFORE CODED THUNDER WHERE CAPE IS 1000 J/KG OR GREATER. PCPN
ACTIVITY WILL BE CONCENTRATED OVER THE HIGHER ELEVATION AND
WESTERN SLOPES INTO 12Z FRIDAY. THE ATMOSPHERE WILL REMAIN
UNSTABLE FRIDAY...BUT PCPN ACTIVITY WILL DIMINISH IN COVERAGE AS
RAINFALL MOVE OVER THE EASTERN MOUNTAINS BY 06Z.

THE NAM SHOWS SFC CAPE VALUES INCREASING FROM THE NORTH TO 1200 J/KG
AND SINKS SOUTH TO THE REST OF THE AREA THURSDAY AFTERNOON AND
EVENING..

THUNDER POTENTIAL SHOULD BE SOMEWHAT DIURNALLY DRIVEN. PRECIPITABLE
WATER VALUES SHOULD BE LOWER THAN 0.750 INCHES...SO THAT SHOULD
LIMIT THE QPF A BIT.

WENT WITH THE SUPERBLEND GUIDANCE FOR TEMPERATURES THROUGH THE
PERIOD.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
USED AN BLEND OF THE OPERATIONAL MODELS AND ENSEMBLE MEANS FOR
FRIDAY NIGHT INTO SATURDAY. THIS HAS THE UPPER LOW MOVING OFF TO THE
EAST FRIDAY NIGHT. A WARM FRONT THEN PUSHES NORTHWARD THROUGH THE
AREA ON SATURDAY...FOLLOWED BY ANOTHER COLD FRONT ON SUNDAY.

FOR THE BEGINNING OF THE WORK WEEK...TRANSITIONED TO A BLEND OF THE
ECMWF...CANADIAN...AND ECMWF ENSEMBLE MEAN.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
13Z WEDNESDAY THRU 12Z THURSDAY...

830 AM UPDATE. INSERTED MORE NUMEROUS SHOWERS EAST OF PKB-CRW LINE
THAT WILL END FROM SOUTHWEST TO NORTHEAST LATER THIS
MORNING...WITH MVFR/LOCALLY IFR CONDITIONS IN THE HEAVIER SHOWERS.
THEN COMES THE BREAK IN SHOWERS/STORMS BEFORE A COLD FRONT COMES
IN FROM THE WEST LATER THIS AFTERNOON. EXPECT MOST LOCATIONS TO
BE VFR BY 17Z...AND CONTINUE UNTIL THE FRONTAL BAND OF
SHOWERS/STORMS ARRIVES. WINDS WILL BE SOUTHWEST 5 TO 8 KTS AHEAD
OF THE FRONT.

PREVIOUS DISCUSSION...
WIDESPREAD MVFR CEILINGS THIS MORNING WILL SLOWLY LIFT
THROUGH THE DAY. MVFR MORNING CIGS MAY PERSIST UNTIL LATER THIS
AFTERNOON...BUT STILL NOT CERTAIN THAT WILL BE THE CASE AS FRONT
APPROACHES LATER TODAY. A COLD FRONT WILL BRING SHOWERS AND
THUNDERSTORMS BY LATE AFTERNOON AND EARLY THIS EVENING AND
POSSIBLY A RETURN TO MVFR OR IFR CONDITIONS IN SHOWERS AND
THUNDERSTORMS.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z THURSDAY...

FORECAST CONFIDENCE: MEDIUM.

ALTERNATE SCENARIOS: COLD FRONTAL BAND OF SHOWERS/STORMS MAY BE A
LITTLE FASTER THAN FORECAST.

THE TIMING OF SHOWERS AND THUNDERSTORMS ARRIVING FROM THE WEST ON
THIS AFTERNOON MAY ALSO VARY AS MODELS STILL DIFFER.
THUNDERSTORMS MAY BRING IFR CONDITIONS AND CONTAIN SMALL HAIL OR
GRAUPEL WEDNESDAY AFTERNOON.

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       12   13   14   15   16   17   18   19   20   21   22   23
EDT 1HRLY       08   09   10   11   12   13   14   15   16   17   18   19
CRW CONSISTENCY  M    M    M    M    M    H    H    H    H    H    H    H
HTS CONSISTENCY  M    M    H    H    H    H    H    H    M    M    M    M
BKW CONSISTENCY  L    L    M    M    M    M    M    H    H    H    H    H
EKN CONSISTENCY  L    M    M    M    M    H    M    H    H    H    H    H
PKB CONSISTENCY  M    M    M    M    H    H    H    H    H    H    H    H
CKB CONSISTENCY  L    M    M    M    M    H    M    H    H    H    H    H

AFTER 12Z THURSDAY...
IFR POSSIBLE IN SHOWERS THROUGH THURSDAY AFTERNOON.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.

&&

$$
SYNOPSIS...ARJ/JMV/MPK
NEAR TERM...JMV/MPK
SHORT TERM...ARJ
LONG TERM...RPY
AVIATION...JMV/MPK


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