313
FXUS61 KRLX 240136
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
936 PM EDT SUN SEP 23 2018
SYNOPSIS
FRONTAL BOUNDARY WILL REMAIN NEARLY STATIONARY OVER THE AREA
THROUGH LATE TONIGHT. THE FRONT LIFTS NORTH AS A WARM FRONT BY
MONDAY NIGHT. ANOTHER COLD FRONT MOVES IN BY MIDWEEK.
NEAR TERM /THROUGH MONDAY/
AS OF 936 PM SUNDAY...
LATEST RADAR MOSAIC SHOWS RAIN SHIELD THAT HAD BEEN IMPACTING
MUCH OF THE AREA HAS PUSHED NORTHEAST WITH ONLY SOME ISOLATED
POCKETS OF RAIN ACROSS THE SOUTHWEST COUNTIES.
LATEST HI-RES MODELS INDICATE THIS TREND WILL CONTINUE
OVERNIGHT WITH THE RAIN INCREASING IN AREAL COVERAGE LATER
TONIGHT.
WITH THIS IN MIND, HAVE MADE SOME CHANGES TO THE POP AND WX
GRIDS TO REFLECT THIS THINKING.
AS OF 350 PM SUNDAY...
RADAR IMAGERY SHOWS AREAS OF STRATIFORM RAIN, LIGHT TO MODERATE
ACROSS NORTHEAST KY, SOUTHWEST AND CENTRAL WV MOVING EAST
NORTHEAST PARALLEL TO A NEARLY STATIONARY FRONTAL BOUNDARY. THIS
FRONT WILL OSCILLATE OVERHEAD THROUGH TONIGHT. RAINFALL AMOUNTS
SEEM OVERDONE BY ALL MODELS. HALF TO 3/4 OF AN INCH OF RAIN HAS
BEEN REPORTED IN PERIODS OF 6 HOURS. NOT ENOUGH TO CAUSE
FLOODING. HOWEVER, ACCOUNTING FOR ADDITIONAL RAINFALL TONIGHT.
THEREFORE, THE FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH 10Z
MONDAY.
IN OTHER HAND, MODELS THETA-E FIELDS INDICATE A PACKED GRADIENT
JUST NORTH OF OUR CWA SEPARATING A JUICY AIRMASS, SOUTH OF THE
BOUNDARY, FROM A DRIER AIRMASS NORTH OF THE BOUNDARY. MODELS
SUGGEST THAT H850 WINDS WILL TURN FROM THE SOUTH BY 06Z TONIGHT,
LIFTING THE STATIONARY FRONT NORTH, AS A WARM FRONT MONDAY
MORNING. AT THE SAME TIME, H500 CHARTS SHOW A SERIES OF
VORTICITY MAXIMA RIDING NORTH NORTHEAST, ALONG AND EAST OF THE
OH RIVER, UNDER PWATS NEAR 2 INCHES, LIMITED BUOYANCY, AND POOR
DEEP LAYERED SHEAR. THESE PARAMETERS SUGGEST LIMITED CONVECTION
AND MORE STRATIFORM RAIN WOULD OCCUR.
THERE IS CONSENSUS AMONG THE HRRR, NAM, ECMWF, AND AT SOME
DEGREE THE RAP13, THAT SUGGESTS A LULL IN PCPN, SPREADING FROM
EXTREME SOUTHWEST VA, NORTH, ROUGHLY OVER THE EASTERN HALF OF
THE AREA AFTER 06Z TONIGHT THROUGH MONDAY AFTERNOON. THE REST OF
MODELS BRING ADDITIONAL AREAS OF RAIN ACROSS THE ENTIRE AREA.
PREFER THE MODEL CONSENSUS AND CODED HIGHER POPS ACROSS
SOUTHEAST OH ACCORDINGLY. ADDITIONAL PCPN IS EXPECTED AS THE MID
LEVEL SHORTWAVES MOVE NORTH ACROSS SOUTHEAST OH MONDAY, AND
ACROSS THE REST OF THE AREA MONDAY NIGHT. THESE SHORTWAVES COULD
PRODUCE MODERATE TO HEAVY RAIN, POSING A THREAT FOR FLOODING
OVER AREAS THAT ARE NEARLY SATURATED. A FLASH FLOOD WATCH
CONTINUES IN EFFECT FOR NORTHEAST KY, AND PORTIONS OF SOUTHEAST
OH AND WV THROUGH 10Z OVERNIGHT TONIGHT, BUT IT WILL LIKELY BE
EXTENDED THROUGH MONDAY NIGHT, OR RE-ISSUE AS A NEW WATCH TO
DEAL WITH THE UPCOMING RAINFALL.
CLOUDINESS, COOLING RAIN, AND DEWPOINTS IN THE 50S UNDER LIGHT
NORTHERLY FLOW WILL KEEP TEMPERATURES IN THE COOL SIDE, MORE
NOTICEABLE NORTHERN SECTIONS. IN FACT, WENT COOLER THAN ALL
GUIDANCE FOR LOWS TONIGHT, PERHAPS A DEGREE OR TWO ABOVE THEIR
EXPECTED DEWPOINTS. WENT CLOSER TO THE NBM FOR HIGHS ON MONDAY.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/
AS OF 500 PM SUNDAY...
THIS SHOULD BE THE GRAND FINALE TO A WET MONTH ACROSS THE AREA
AS AN UNSETTLED PERIOD OF WEATHER PERSISTS MUCH OF THE TIME AS
THE AREA REMAINS IN THE WARM SECTOR. INITIALLY ON MONDAY NIGHT
A WARM FRONT IS SHOWN BY THE MODELS TO BE LIFTING NORTH ACROSS
EASTERN OHIO AND WESTERN/CENTRAL PENNSYLVANIA AND A COLD FRONT
WORKING IN FROM FURTHER BACK IN THE MIDWEST. THE OPERATIONAL
MODELS CONTINUE TO SHOW SOME RUN TO RUN AND MODEL TO MODEL
DIFFERENCES IN THE PLACEMENT OF THE HEAVIEST QPF. BASED ON
SYNOPTICS WHICH SHOW AN EXITING 60 KT+ JET STREAK OVER OHIO AND
PENNSYLVANIA ALONG AND NORTH OF THE WARM FRONT AND SEVERAL MID-
LEVEL RIPPLES OF ENERGY NEAR AND JUST NORTH OF THE WARM FRONT
ONE AREA FOR MODERATE TO HEAVIER RAIN ON MONDAY NIGHT SHOULD BE
OVER OUT NORTHERN COUNTIES IN WEST VIRGINIA ALONG AND NORTH OF
THE WARM FRONT WHERE LIFT FROM THE FRONT AND SUPPORT ALOFT IS
EFFECTIVE AT GENERATING PRECIPITATION. A SECOND AREA SHOULD BE
OVER OUR NORTHWESTERN COUNTIES IN OHIO, CLOSEST TO THE
APPROACHING COLD FRONT WHERE AMPLE LIFT AND A HIGH MOISTURE
CONTENT (PWATS NEAR 1.95 INCHES) ARE SHOWN. FURTHER SOUTH AND
EAST OF CHARLESTON THESE AREAS MAY NOT SEE MUCH IN THE WAY OF
SHOWERS OR THUNDERSTORMS MONDAY NIGHT AS THESE LOCATIONS REMAIN
AWAY FROM THE BEST LIFT AND SUPPORT ALOFT. POPS LEAN TOWARD THE
ECMWF WHICH SEEMS TO HAVE THE MOST REASONABLE FEEL FOR THE
LARGER SCALE FEATURES AND PLACEMENT OF HEAVIER QPF. SOME MODELS
SUCH AS THE 12Z OPERATIONAL GFS LOOKED A LITTLE DRY IN SPOTS IN
THIS TIME FRAME. THERE WILL BE A THREAT FOR HEAVY RAIN ACROSS
OUR OHIO AND NORTHERN WEST VIRGINIA COUNTIES IN THE MONDAY NIGHT
TIME FRAME AND POSSIBLE PONDING OF WATER AND FLOODING WILL NEED
TO BE WATCHED FOR ALONG WITH AREAS OF DENSE FOG. LOWS SHOULD BE
ABOUT 10-15 DEGREES ABOVE NORMAL MONDAY NIGHT.
ONCE THE WARM FRONT LIFTS NORTH OF THE AREA ON TUESDAY, THE MAIN
FOCUS WILL SHIFT TO THE INCOMING COLD FRONT. ALL MODELS,
INCLUDING THE GFS, NOW HAVE A FASTER TIMING WITH THE FRONT OVER
MOST OF AREA INITIALLY. FOR TUESDAY, WE SHOULD REMAIN IN THE
WARM SECTOR WITH REALLY AN ANYTIME CHANCE OF SHOWERS AND
THUNDERSTORMS WITH CHANCES. THE MAIN THING THAT MAY IMPACT
TIMING IS WEAKER PIECES OF MID-LEVEL ENERGY MOVING NORTHEAST
ACROSS THE AREA WITHIN THE WARM SECTOR. SURFACE COMPUTED CAPE
VALUES ARE SHOWN BY THE GFS TO BE OVER 1500 J/KG WEST OF THE
OHIO RIVER IN OUR AREA ON TUESDAY AFTERNOON WHICH MAY HELP SOME
HEALTHIER CONVECTION TO GET GOING. MODELS CONTINUE TO FOCUS SOME
OF THE HIGHER QPF AMOUNTS OVER OUR NORTHWESTERN COUNTIES IN THIS
TIME FRAME AS A RESULT. DEPENDING ON HOW MUCH SUN WET GET, HIGHS
MAY REACH INTO THE LOWER 80S IN WARMER VALLEY LOCATIONS
ESPECIALLY IN THE SOUTHERN HALF OF THE AREA.
THE COLD FRONT STARTS TO WORKING EAST TUESDAY NIGHT INTO
WEDNESDAY MOVING FROM INDIANA ACROSS OHIO. PWATS STAY SOLIDLY IN
THE 1.90-2.10 INCH RAIN IN OUR AREA, WHICH REMAINS AT OR ABOVE
THE HIGHEST 90 PERCENT THRESHOLD BASED ON SPC SOUNDING
CLIMATOLOGY. AN 80 KT+ JET STREAK IS PROGGED TO MOVE OVERHEAD
AT 250 MB COMBINED WITH SOME SUBTLE MID-LEVEL RIPPLES OF ENERGY
WHICH SHOULD FURTHER AID IN LIFTING OF THE AIR AND GENERATING
HEAVY RAIN. THIS WILL CONTINUE TO RESULT IN THE THREAT OF
PONDING OF WATER IN POOR DRAINAGE AREAS AND POSSIBLE FLOODING
WITH AN EYE NEEDING TO BE KEPT ON AREA RIVERS GIVEN ANTECEDENT
CONDITIONS (I.E. SATURATED SOILS FROM RECENT RAINS). IN
ADDITION, GFS SURFACE COMPUTED CAPE VALUES ARE SHOWN TO BE OVER
1500 J/KG ACROSS THE ENTIRE AREA WITH SOME AREAS OVER 2000 J/KG
IN WEST VIRGINIA. LIS OF -3 TO -5 ARE SHOWN AS WELL ALONG WITH
SPEED SHEAR IN FORECAST SOUNDINGS. THUS A THREAT FOR STRONG TO
SEVERE THUNDERSTORMS WILL ALSO EXIST, WITH THE MAIN HAZARD
LIKELY DAMAGING WINDS AS SOME SORT OF LINEAR ORGANIZED
CONVECTION LOOKS FAVORED WITH THE APPROACHING COLD FRONT. LOWS
TUESDAY NIGHT WILL REMAIN 10-15 DEGREES ABOVE NORMAL AND HIGHS
ON WEDNESDAY SHOULD BE NEAR TO A FEW DEGREES ABOVE NORMAL.
LONG TERM /THURSDAY THROUGH SUNDAY/
AS OF 510 PM SUNDAY...
THE FRONT ITSELF IS EXPECTED TO CROSS THE CENTRAL AND EASTERN
PORTIONS OF THE AREA WEDNESDAY NIGHT AND EXIT BY THURSDAY
MORNING. THE THREAT FOR HEAVY RAIN AND STRONG TO SEVERE
THUNDERSTORMS WILL LINGER INTO THESE AREAS FOR THE FIRST PART
OF WEDNESDAY NIGHT THEN END WITH THE PASSAGE OF THE COLD FRONT.
HOWEVER, CLEARING ON THE BACK SIDE OF THE FRONT AWAY FROM THE
NORTHWESTERN COUNTIES IN OHIO WILL BE SLOW TO COME BY AS THE
COLD FRONT STARTS TO SLOW DOWN AS IT MOVES TOWARD SOUTHERN
VIRGINIA AND BECOMES PARALLEL TO THE MID AND UPPER LEVEL FLOW
ALOFT. THIS COMBINED WITH SOME LINGERING MID-LEVEL ENERGY ALONG
THE FRONT SHOULD HELP TO KEEP CLOUDS AND THE POSSIBILITY OF
LIGHTER RAIN SHOWERS AROUND OVER THE ASTERN MOUNTAINS AND
ADJACENT LOWLANDS INTO THURSDAY AND THURSDAY NIGHT. WE DID
DECREASE CLOUD COVER SOME AND LOWER POPS OVER THE NORTHWEST
THIRD OF THE AREA WHERE THE MODEL CONSENSUS IS BETTER FOR THE
FRONT TO PULL AWAY FROM. 850 MB TEMPS DROP A FEW DEGREES BEHIND
THE FRONT SO THERE SHOULD BE SOME A SLIGHT DROP IN TEMPERATURES
BUT NOTHING SIGNIFICANT WITH HIGHS NEAR NORMAL THURSDAY AND LOWS
STILL 5-8 DEGREES ABOVE NORMAL THURSDAY NIGHT.
ANY 'COOLING' WILL BE VERY SUBTLE WITH THE FLOW ALOFT GOING
QUASI-ZONAL FOR FRIDAY. MODELS ARE NOW BRINGING ANOTHER BATCH OF
ENERGY INTO THE GREAT LAKES BY NEXT WEEKEND WHICH FOR NOW SHOULD
STAY FAR ENOUGH NORTH OF THE AREA TO KEEP THINGS DRY. HOWEVER,
MID AND HIGH LEVEL CLOUDS MAY MAKE A RETURN ESPECIALLY BY LATER
SATURDAY INTO SUNDAY. OTHERWISE EXPECT LOWS ABOUT 3-5 DEGREES
ABOVE NORMAL ON SATURDAY AND 5-7 DEGREES ABOVE NORMAL ON SUNDAY
WITH HIGHS NEAR TO A FEW DEGREES ABOVE NORMAL SATURDAY AND
NEARING 5 DEGREES ABOVE NORMAL SUNDAY. THE NBM MODEL WAS MAINLY
FOLLOWED FOR TEMPERATURES.
AVIATION /02Z MONDAY THROUGH FRIDAY/
AS OF 746 PM SUNDAY...
RADAR IMAGERY AND SFC OBS CONTINUE TO SHOW IFR/LIFR CONDITIONS
UNDER LIGHT TO MODERATE RAIN EXTENDING FROM NORTHEAST KY,
NORTHEAST INTO OUR NORTHEAST MOUNTAINS. OUTSIDE OF THE
PRECIPITATION, VFR/MVFR CONDITIONS PREVAILED.
THE AREA OF RAIN IS PUSHING SLOWLY EAST WHICH SHOULD BRIEFLY
ALLOW AREAS TO THE WEST TO IMPROVE. HOWEVER, IFR CONDITIONS MAY
DEVELOP AS LOW CLOUDS AND/OR FOG DEVELOP.
MODELS SUGGEST THE LULL IN PCPN SPREADING FROM WEST TO EAST
WILL CONTINUE. HOWEVER, ABUNDANT LOW LEVEL MOISTURE, CLOUDINESS
AND FORCING ALOFT WILL BRING AREAS OF RAIN AND ASSOCIATED IFR
CONDITIONS, ONCE AGAIN SPREADING FROM WEST TO EAST BY 12Z.
FRONT WILL MOVE NORTH OF THE AREA LATER ON MONDAY, KEEPING HIGH
PROBABILITIES FOR RAIN AND IFR CONDITIONS ACROSS SOUTHEAST OH
AND NORTHERN WV.
EXPECTING WIDESPREAD IFR/LIFR IN POST RAIN FOG AND LOW STRATUS
ON MONDAY. LIGHT NORTHEASTERLY WINDS THROUGH THE PERIOD.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS
ALTERNATE SCENARIOS: TIMING OF PCPN AND CHANGE OF CONDITIONS
TONIGHT AND MONDAY MAY VARY FROM FORECAST. MORE LIFR AND VLIFR
CONDITIONS ARE POSSIBLE LATE TONIGHT THAN CURRENTLY FORECAST.
AFTER 00Z TUESDAY...IFR AT TIMES IN SHOWERS AND THUNDERSTORMS
AND POST RAIN STRATUS AND FOG THROUGH AT LEAST MID WEEK.
RLX WATCHES/WARNINGS/ADVISORIES
WV...FLASH FLOOD WATCH THROUGH MONDAY AFTERNOON FOR WVZ005>008-
013>020-024>032-034-039-040-515>526.
OH...FLASH FLOOD WATCH THROUGH MONDAY AFTERNOON FOR OHZ086-087.
KY...FLASH FLOOD WATCH THROUGH MONDAY AFTERNOON FOR KYZ101>103-105.
VA...NONE.
SYNOPSIS...ARJ
NEAR TERM...JSH/ARJ
SHORT TERM...STACHELSKI
LONG TERM...STACHELSKI
AVIATION...JSH
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