Heavy Rain in West Virginia, August 19, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
810 PM EDT THU AUG 18 2011

.SYNOPSIS...
UPPER LEVEL DISTURBANCES IN NORTHWEST FLOW WILL PROVIDE
OPPORTUNITIES FOR SHOWERS AND THUNDERSTORMS AT TIMES THROUGHOUT
THE WEEKEND.  A SOMEWHAT STRONGER COLD FRONT CROSSES SUNDAY NIGHT.

&&

.NEAR TERM /THROUGH FRIDAY/...
ISOLATED CONVECTION OVER SE WV AND OVER E CNTRL OH...THE LATTER OUT
AHEAD OF A COLD FRONT UP NEAR LAKE ERIE...SHOULD FADE WITH
DARKNESS.  SCATTERED CONVECTION ASSOCIATED WITH UPPER LEVEL S/W
TROUGH OVER THE LOWER OHIO VALLEY WILL CROSS OVERNIGHT.  NOCTURNAL
TIMING SUGGEST JUST CHANCE POPS DECREASING TO SLIGHT CHANCE BY DAWN
FRI WITH OVERALL FORCING AND MOISTURE MEAGER.

WEAK LAKE ERIE COLD FRONT WILL BE PUSHING S INTO THE AREA FRI.
WHATEVER IS LEFT OF THE BOUNDARY WILL BE ACROSS THE CENTRAL CWA BY
18Z.  KEPT CHANCE POPS MAINLY ALONG AND EAST OF THIS FOR DEVELOPMENT
DURING PEAK HEATING.  CAPPING MAY CONTINUE TO BE AN ISSUE IN SOME
AREAS THOUGH...AND WITH WEAK MIDLEVEL FLOW SEE LITTLE CHANCE FOR
SIGNIFICANT CONVECTION THOUGH ANYTHING THAT DOES STAND UP WILL BE
SLOW MOVING AND THUS PERSISTENT.  MID LEVEL DRY AIR PUSHES S INTO N
WV ESPECIALLY IN THE MOUNTAINS FRI AFTERNOON.

ANOTHER UPPER LEVEL S/W TROUGH APPROACHES SW PORTION OF FORECAST
AREA LATE FRI.

STUCK CLOSER TO BIAS-CORRECTED MOSGUIDE GRID TONIGHT FOR MIN
TEMPS...GENERALLY HIGHER THAN MET/MAV.  NUDGED UP FRIDAY HIGHS BUT
STILL CAME IN A TOUCH BELOW MOS.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
LOOKS LIKE OUR AREA WILL BE MOSTLY IN BETWEEN 2 SYSTEMS THAT WILL BE
TRACKING EAST SOUTHEAST IN THE CONTINUING NORTHWEST FLOW ALOFT. IN
DEALING WITH RATHER MODEST MULTIPLE SHORT WAVES IN THIS FLOW PATTERN
AT THIS TIME OF YEAR...THE MODELS DO HAVE DIFFERENCES. PERHAPS THE
BIGGEST DIFFERENCE IS WITH THE BEGINNING OF THE PERIOD. MODELS DO
IDENTIFY ONE WEAK SHORT WAVE EXITING THE AREA EARLY FRIDAY
NIGHT...SO WEAK THAT IT LEAVE A FRONT TO DISSIPATE SOMEWHERE OVER
OUR AREA BY FRIDAY NIGHT. ANY LEFT OVER SHOWERS FROM THIS EXITING
SYSTEM WILL BE EARLY FRIDAY NIGHT IN THE EAST...THEN DRYING AS WEAK
HIGH PRESSURE MOVES IN FOR LATER FRIDAY NIGHT AND SATURDAY. THE
MODEL DIFFERENCE MENTIONED BEFORE IS THAT THE GFS HAS A FEED BACK
PROBLEM ON THUNDERSTORM COMPLEX FURTHER BACK OVER THE IOWA EARLIER
FRIDAY AND DRIVES ITS CONVECTIVELY INDUCED VORT MAX EASTWARD ACROSS
OUR AREA FRIDAY NIGHT....GIVING US HIGH POPS. BELIEVE THIS ACTIVITY
OUT WEST WILL WAIT FOR THE SECOND SYSTEM. THUS...THE GFS IS AN
OUTLIER SOLUTION...AND ESPECIALLY WITH A FEED BACK PROBLEM...WILL
IGNORE THIS SOLUTION AND GO WITH THE NAM FOR DETAILS.

THIS ENTAILS ENDING SHOWERS EARLY FRIDAY NIGHT IN THE
EAST...FOLLOWED BY SUNSHINE AND DRY SATURDAY.MODELS AGREE MORE ON
NEXT MORE WELL DEFINED SYSTEM AND FRONTAL SYSTEM APPROACHING
SATURDAY NIGHT AND BEYOND. WILL BRING CLOUDS IN SATURDAY NIGHT WITH
CHANCE POPS OVERSPREADING THE AREA FROM THE WEST.

MODELS AGREE TEMPERATURES WILL BE WELL UP INTO THE 80S SATURDAY WITH
THE SUNSHINE...WHILE LOWS WILL BE IN THE 60S.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
BASICALLY WENT WITH HPC THINKING. COLD FRONT...WITH SHOWERS AND
THUNDERSTORMS...PUSHES SOUTHEAST ON SUNDAY...WITH HIGH PRESSURE
BUILDING IN. SURFACE HIGH PRESSURE...ALONG WITH DRIER AND COOLER
WEATHER...SHOULD FULLY BE IN CONTROL OF OUR WEATHER MONDAY NIGHT
INTO WEDNESDAY. AS HIGH CENTER PUSHES SOUTHEAST...SOUTHERLY WINDS
SHOULD RESULT IN WARMER TEMPERATURES ON THURSDAY.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
VERY WARM AND SOMEWHAT HUMID AIR REMAINS IN PLACE UNDER UPPER LEVEL
NW FLOW.  THIS MEANS A FEW SHOWERS AND THUNDERSTORMS AROUND FROM
TIME TO TIME.  TRIGGERS INCLUDE AN UPPER LEVEL DISTURBANCE CROSSING
LATE OVERNIGHT...A VERY WEAK FRONT MOVING SLOWLY SWD FRI...AND
ANOTHER UPPER LEVEL DISTURBANCE LATE FRI NT.

DENSE VALLEY FOG WILL FORM OVERNIGHT...ALTHOUGH IT COULD BE
INTERRUPTED BY CLOUDS ASSOCIATED WITH SHOWERS AND THUNDERSTORMS.

FLOW WILL BE LIGHT AND VARIABLE AT THE SURFACE AND LATE MAINLY W
ALOFT.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SATURDAY...

FORECAST CONFIDENCE: MEDIUM.

ALTERNATE SCENARIOS: AS NOTED ABOVE...FOG OCCURRENCE IS DEPENDENT ON
TIMING OF CLOUD ARRIVAL.

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.

DATE                                                            FRI 08/19/11
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EDT 1HRLY       20   21   22   23   00   01   02   03   04   05   06   07
CRW CONSISTENCY  H    H    H    H    M    M    M    L    L    L    L    L
HTS CONSISTENCY  H    H    H    H    M    M    M    L    L    L    L    L
BKW CONSISTENCY  H    M    M    M    H    H    H    H    H    H    H    H
EKN CONSISTENCY  H    M    M    M    L    L    L    L    L    M    L    L
PKB CONSISTENCY  H    H    H    M    M    M    L    L    L    L    L    L
CKB CONSISTENCY  H    H    H    H    M    M    M    L    L    L    L    L

AFTER 00Z SATURDAY...
NO WIDESPREAD AREAS OF IFR ARE EXPECTED.

&&

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

&&

SYNOPSIS...TRM
NEAR TERM...CL/TRM
SHORT TERM...JMV
LONG TERM...JSH
AVIATION...TRM