Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 301425
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1025 AM EDT SAT APR 30 2016

.SYNOPSIS...
WARM FRONT TODAY. UNSTABLE SUNDAY WITH COLD FRONT SINKING SOUTHEAST
SUNDAY NIGHT. DRIER MONDAY. WAVE PASSES TO THE SOUTHEAST TUESDAY.
LARGE UPPER TROUGH BRINGS COOL AND UNSETTLED WEATHER TOWARDS END
OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
10 AM UPDATE...INCREASED POPS/QPF THROUGH TONIGHT. LARGE SCALE
RAIN WAS CONCERNING ENOUGH TO ISSUE FLASH FLOOD WATCH ESPECIALLY
SINCE THERE SHOULD BE EMBEDDED CONVECTIVE CELLS AS EVIDENCED BY
REGIONAL RADAR RETURNS AND MODEL CONVECTIVE FEEDBACK SIGNATURES.

PREVIOUS DISCUSSION FOLLOWS...A WARM FRONT WILL GRADUALLY LIFT
NORTH...BRINGING SCATTERED TO NUMEROUS SHOWER WITH EMBEDDED
THUNDERSTORMS THIS AFTERNOON AND EVENING. HIGH RESOLUTION MODELS
ARE IN AGREEMENT WITH THE ONSET OF PCPN OVER SOUTHERN WV AND
NORTHEAST KY BY 18Z SATURDAY. PRECIPITABLE WATER ABOUT 1.25
INCHES...DECENT DEEP LAYER SHEAR ABOUT 45 KNOTS...BUT LOW SFC CAPE
WILL COMBINE TO PRODUCE MAINLY SHOWERS THROUGH TONIGHT.

MODELS INDICATE H850 TEMPERATURES WILL BE AROUND 12C THROUGH THE
PERIOD. TEMPERATURES WILL BE MILD DUE TO CLOUD COVER AND COOLING
SHOWERS...GENERALLY IN THE LOWER 70S LOWLANDS...RANGING INTO THE
LOWER 60S HIGHER ELEVATIONS.  WENT CLOSER TO THE NATIONAL BLEND OF
MODELS FOR TEMPERATURES THROUGH THE PERIOD.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
SHOULD HAVE A BRIEF LULL IN THE SHOWER ACTIVITY SUNDAY ACROSS THE
CENTRAL TO WESTERN FORECAST AREA AFTER WARM FRONTAL PASSAGE AND BEFORE
COLD FRONT APPROACHES IN THE AFTERNOON. GUIDANCE INDICATES MODEST
INSTABILITY LATER SUNDAY WITH CAPE VALUES IN THE 1000 - 1500 J/KG
RANGE AND HEIGHT FALLS AS SHORTWAVE APPROACHES SUNDAY EVENING
WILL STEEPEN LAPSE RATES CLOSE TO 7C/KM. ALSO OF NOTE WILL BE
0-6KM SHEAR VALUES OF 40 - 50KTS...WHICH SUPPORTS ORGANIZED
UPDRAFTS. BIG QUESTION WILL BE HOW MUCH SUN POKES THROUGH DURING
THE DAY TO FURTHER ADD TO THE INSTABILITY...AS LOW CLOUDS MAY
LINGER ACROSS MUCH OF THE AREA DUE TO THE EARLY MORNING
ACTIVITY.  EVEN SO WE SHOULD STILL HAVE ENOUGH FORCING WITH THE
COLD FRONT TO KICK OFF SOME STRONGER THUNDERSTORMS...WITH SOME POSSIBLY
CONTAINING GUSTY WINDS AND HAIL. SPC HAS EXTENDED A MARGINAL RISK
AREA FOR SEVERE STORMS ACROSS THE REGION. ANY STORMS THAT DO
DEVELOP WILL HAVE TO BE CAREFULLY MONITORED FOR FLASH FLOODING...ESPECIALLY
AFTER THE HEAVY RAIN FROM SATURDAY NIGHT INTO SUNDAY MORNING THAT
WILL PRIME THE AREA.

HIGH PRESSURE AND RIDGING SHOULD GIVE US A BRIEF REPRIEVE FROM
STORMY CONDITIONS ON MONDAY...HOWEVER THE PROGRESSIVE PATTERN WILL
MAKE ANY BREAK IN THE ACTION SHORT LIVED AS NEXT SHORT WAVE COULD
ARRIVE AS EARLY AS LATE MONDAY NIGHT INTO TUESDAY.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
08Z MORNING UPDATE...ENSEMBLE AND OPERATIONAL MODELS ARE COMING
INTO BETTER AGREEMENT FOR THE END OF NEXT WEEK...WITH LARGE UPPER
LOW/TROUGH BECOMING ENTRENCHED OVER THE REGION. THIS PATTERN WILL
LIKELY BRING COOL AND UNSETTLED CONDITIONS TO THE REGION. HAVE
DECIDED TO GO AHEAD AND UPDATE THE LONG TERM FOR TEMPERATURES THU-
SAT. IN THIS PATTERN...TEMPERATURES ARE LIKELY TO BE UNSEASONABLY
COOL AND SOME WINTRY PRECIPITATION COULD BE POSSIBLE ACROSS THE
HIGHER TERRAIN IN THE EASTERN FORECAST AREA.

PREVIOUS DISCUSSION...
MODELS STILL DIFFER ON WAVE CROSSING THE MIDDLE ATLANTIC STATES
TUESDAY INTO WEDNESDAY...BUT THERE IS INCREASING CONSENSUS ITS
MOISTURE AFFECTS AT LEAST SOUTHEASTERN PORTIONS OF THE FORECAST
AREA.

MODELS ALSO REMAIN A BIT OUT OF SYNC WITH A COUPLE OF NORTHERN
STREAM SYSTEMS THAT CROSS MID TO LATE WEEK. THE GFS BRINGS COLD
FRONTS ACROSS LATE WEDNESDAY AND THEN FRIDAY NIGHT...WHILE THE
ECMWF TIMING IS EARLY THURSDAY ON THE FIRST COLD FRONT...AND THEN
IT JUST CLOSES OFF A LARGE UPPER LOW THAT THEN SLOWLY LUMBERS
THROUGH THE AREA AT LEAST THE END OF THE PERIOD. THE GFS IS
FARTHER NORTH AND DEEPER WITH THE UPPER LOW...HENCE THE MORE
DEFINED SECOND SURFACE FRONT. AS FOR THE UPPER LOWS...THIS IS A
CLASSIC CASE OF DEEPER...BY ABOUT 350M...AND FARTHER NORTH VERSUS
WEAKER AND FARTHER SOUTH.

THE CURRENT FORECAST BRINGS FRONTS AND THE ASSOCIATED CHANCE FOR
SHOWERS ACROSS WEDNESDAY AND FRIDAY NIGHTS...SIMILAR TO THE WPC
DEPICTION.

KEPT LOWS CLOSE TO PREVIOUS FORECAST AND A GUIDANCE BLEND. BLENDED
IN GFS-BASED GUIDANCE FOR HIGHS...A LITTLE LOWER THAN PREVIOUS
FORECAST FOR THE MOST PART.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
A WARM FRONT LIFTS NORTH TODAY...WITH SCATTERED SHOWERS AND
ISOLATED STORMS. WIDESPREAD MVFR CONDITIONS CAN BE EXPECTED AFTER
15-18Z...UNDER PERIODS OF RAIN OR THUNDER. PCPN SHOULD REACH HTS
AND CRW AROUND 16Z TODAY...AND SPREAD NORTH THROUGH THIS EVENING.
PERIODS OF IFR ARE POSSIBLE IN SHOWERS.

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

FORECAST CONFIDENCE: MEDIUM.

ALTERNATE SCENARIOS: TIMING AND INTENSITY OF SHOWERS AND STORMS
COULD VARY...AND PRODUCE IFR CONDITIONS OR WORST ALONG THEIR
PATH.

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  H    H    H    H    M    M    M    M    M    M    M    M
HTS CONSISTENCY  H    H    H    M    M    M    M    M    M    M    M    M
BKW CONSISTENCY  H    H    H    M    M    M    M    M    M    M    M    M
EKN CONSISTENCY  H    H    H    H    H    H    M    M    M    M    M    M
PKB CONSISTENCY  H    M    H    H    H    H    M    M    M    M    M    M
CKB CONSISTENCY  H    H    H    H    H    H    H    M    M    M    M    M

AFTER 12Z SUNDAY...
IFR POSSIBLE AGAIN THROUGH SUNDAY NIGHT WITH ADDITIONAL ROUNDS OF
SHOWERS AND THUNDERSTORMS..AND IN STRATUS LINGERING INTO MONDAY
MORNING.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...FLASH FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH SUNDAY
     MORNING FOR WVZ005>011-013>020-024>040-046-047.
OH...FLASH FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH SUNDAY
     MORNING FOR OHZ066-067-075-076-083>087.
KY...FLASH FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH SUNDAY
     MORNING FOR KYZ101>103-105.
VA...NONE.

&&

$$
SYNOPSIS...ARJ/JW/MPK
NEAR TERM...ARJ/JW
SHORT TERM...MPK
LONG TERM...TRM/MPK
AVIATION...JW


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