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Area Forecast Discussion
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000
FXUS61 KILN 210555
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
155 AM EDT THU AUG 21 2014

.SYNOPSIS...
A FRONTAL ZONE WILL SETTLE INTO THE OHIO VALLEY TONIGHT. THIS
FRONT WILL GRADUALLY LIFT NORTHEAST INTO THE GREAT LAKES THROUGH
THE WEEKEND. DISTURBANCES WILL INTERACT WITH A MOIST AIRMASS TO
PRODUCE SHOWERS AND THUNDERSTORMS AT TIMES THROUGH THE PERIOD.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
DRY CONDITIONS WILL START OUT THE NEAR TERM. A FEW ISOLATED
SHOWERS ARE DEVELOPING OVER NW OHIO AND ALSO SE INDIANA. THE HI
RES MODELS ARE PICKING UP ON THIS RATHER WELL AND SHOWING
ADDITIONAL DEVELOPMENT INTO NW PORTIONS OF THE FA DURING THE
OVERNIGHT HOURS. INCREASED PRECIPITATION CHANCES IN THIS AREA
OVERNIGHT HOWEVER EXPECT MOST OF THE MORE WIDESPREAD SHOWER AND
THUNDERSTORM ACTIVITY TO HOLD OFF UNTIL THE EARLY DAYTIME HOURS ON
THURSDAY. 

TEMPERATURES HAVE DROPPED OFF INTO THE 60S ACROSS PORTIONS OF THE
AREA. UPPER 60S ARE MORE WIDESPREAD ACROSS NE PORTIONS OF THE FA
WHERE THERE IS LESS CLOUD COVER. THE RATE OF COOLING WILL SLOW
OVERNIGHT AS ADDITIONAL CLOUDS MOVE INTO THE AREA HOWEVER EXPECT
MOST LOCATIONS TO DROP DOWN INTO THE 60S OVERNIGHT.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
THERE IS A LARGE VARIATION IN MODEL SOLUTIONS FOR THURSDAY. PREFER
A NAM/CMC REGIONAL/HIRES-WRF SOLUTION WHICH DROPS H5 ENERGY INTO
THE REGION EARLY THURSDAY MORNING IN THE NW FLOW. THEY PUSH THE
BEST PCPN CHANCE ACROSS THE REGION DURING THE MORNING...AND EXIT
IT OUT OF THE EAST DURING THE AFTN.

THURSDAY NIGHT BETTER FORCING SHIFTS TO NRN OHIO AS CONVERGENCE
ALONG A LIFTING WARM FRONT MOVES ALSO. PUT HIGH CHANCE POPS IN THE
NORTHERN COUNTIES WITH DECREASING POPS DOWN TO THE SW.

ON FRIDAY...ADDITIONAL H5 ENERGY TOPS THE RIDGE AND DROPS SE
ACROSS THE REGION. THIS WILL HELP DEVELOP DAYTIME CONVECTION...BUT
CENTRAL OHIO WILL HAVE THE BEST CHANCE AT SEEING CONVECTION AS IT
IS CLOSER TO THE WARM FRONT.

CONVECTION TOMORROW WILL COMPLICATE THE HIGH TEMPERATURE FORECAST.
ONLY WENT LOWER 80S IN THE NW COUNTIES SINCE THE CONVECTION SHOULD
LIMIT HEATING THERE. SOUTHERN COUNTIES SHOULD BE ABLE TO MAKE THE
MID TO UPPER 80S. AFTER DROPPING DOWN TO ONLY AROUND 70 THURSDAY
NIGHT...FRIDAY IS LOOKING LIKE A HOT AND HUMID DAY. OHIO RIVER
COUNTIES SHOULD SEE TEMPERATURES PUSH INTO THE LOWER 90S WITH
DEWPOINTS IN THE LOWER 70S. THIS WILL PUSH HEAT INDICES OVER 100.
WILL CONTINUE TO HIGHLIGHT THE THREAT IN THE HWO.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AT 12Z ON SATURDAY...THE 20.12Z ECMWF AND GFS ARE VERY GOOD 
AGREEMENT ON THE LARGE SCALE PATTERN WITH AN AMPLIFIED FLOW PATTERN 
OVER THE LOWER 48. A DEEP CLOSED LOW SHOULD BE OVER ID/MT WITH A 
STRONG SUBTROPICAL RIDGE EXTENDING NORTHEAST FROM A 593DM HIGH OVER 
ALABAMA. ANOMALOUS MOISTURE WILL STILL BE IN PLACE WITH PWAT FROM 
1.5 TO 2.0 STANDARD DEVIATIONS ABOVE CLIMO. THROUGH THE WEEKEND THE 
STRONG CLOSED LOW WILL SWING NORTHEAST INTO THE NRN HIGH PLAINS AND 
EVENTUALLY INTO SASK...WHILE THE RIDGE EXPANDS NORTHEASTWARD INTO 
TN/ARK. DESPITE WEAK FORCING...CONTINUED NORTHERLY/NORTHWESTERLY 
FLOW AROUND THE RIDGE...THE PRESENCE OF A WEAK SURFACE TROUGH...AND 
ANOMALOUS MOISTURE SHOULD CONTINUE TO ALLOW FOR STRONG DAYTIME 
INSTBY BOTH SAT AND SUN. THE POTENTIAL FOR ONE MORE CLUSTERS OF SSE 
PROPAGATING STORM CLUSTERS WILL CONTINUE THROUGH THE WEEKEND. GIVEN 
THE MAGNITUDE OF INSTBY...EVEN WITH WEAKENING FLOW WITH TIME...THERE 
COULD BE STRONG/SEVERE STORM THREAT ON EITHER OF THESE DAYS IF A 
ORGANIZED COLD POOL COULD FORM. GETTING INTO MONDAY-TUESDAY...THE 
RIDGE CONTINUES TO BUILD WITH HEAT/HUMIDITY. FLOW BECOMES VERY LIGHT 
THROUGH THE BULK OF THE TROPOSPHERE AND IT BECOMES QUESTIONABLE IF 
COVERAGE OF DAYTIME/EVE STORMS WARRANTS MENTION. RIGHT NOW HAVE RUN 
15-25% RAIN CHANCES BOTH OF THESE DAYS...AND THAT MAY BE TOO HIGH. 
INTO WEDNESDAY...SOME HINTS OF HEIGHT FALLS WHICH MAY ALLOW A LITTLE 
STRONGER FLOW OR A WEAK SHORTWAVE TROUGH TO CROSS THE GREAT LAKES. 
SO A BETTER STORM THREAT THEN...HOWEVER AT THIS TIME RANGE THIS IS A 
VERY LOW CONFIDENCE FORECAST GIVEN CONDITIONAL NATURE OF THE RIDGE 
BUCKLING. 

SO ALL IN ALL...HAVE TENDED TO FOCUS RAIN CHANCES NEAR PEAK HEATING 
INTO THE EVENING AND ALLOW FOR SOME DRY NIGHTS/EARLY MORNINGS. FLY 
IN OINTMENT WILL BE ANY FORWARD PROPAGATING MCS THAT SURVIVES 
THROUGH THE NIGHT...ORIGINATING TO OUR NORTHWEST  AND FALLING DOWN 
NNWLY FLOW EITHER SATURDAY MORNING OR SUNDAY MORNING. LOW CONFIDENCE 
STORM CHANCE...BUT HIGH CONFIDENCE WARM/HUMID PATTERN IS THE STORY 
FOR THE SAT-WED TIMEFRAME.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
THE REGION WILL BE WEDGED BETWEEN TWO SYNOPTIC SCALE SYSTEMS OVER
THE NEXT 24 HOURS. A MID LEVEL CLOSED LOW SLOWLY MOVING FROM THE
EASTERN GREAT LAKES TO NEW ENGLAND AREA. MEANWHILE...A MID LEVEL 
RIDGE WILL TRY TO NUDGE ITS WAY NORTHWARD INTO THE MIDDLE
MISSISSIPPI VALLEY. OUR AREA WILL BE INFLUENCED BY THE NORTHWEST
FLOW ALOFT BETWEEN THESE TWO SYSTEMS ALONG WITH EMBEDDED
DISTURBANCES RIDING SOUTHEAST ON THE EAST SIDE OF THE RIDGE AXIS
FROM TIME TO TIME. AT THE SAME TIME...A WEAK TO MODEST LOW LEVEL
JET WILL BRING SOME LOW LEVEL MOIST ASCENT. MANY MODEL
SOLUTIONS...INCLUDING THE CONVECTION ALLOWING MODELS...CONTINUE TO
STRUGGLE WITH TIMING AND PLACEMENT OF CONVECTION OVER THE NEXT 24
HOURS. THERE IS SOME CONSENSUS IN AT LEAST THE FIRST 12 HOURS. A
WEAK DISTURBANCE OVER NRN INDIANA IS EXPECTED TO MOVE SOUTHEAST
ACROSS NRN OHIO THIS MORNING. ALSO...A LOW LEVEL JET IS FORECAST
TO IMPINGE ON THE REGION FROM THE WEST. WE SHOULD SEE AN INCREASE
IN SHOWERS AND THUNDERSTORMS THIS MORNING...ESPECIALLY BETWEEN 12Z
AND 18Z. HAVE PLACED TEMPO MVFR CONDITIONS AT ALL THE TAF SITES.
FOR THIS AFTERNOON...SOME MODELS SUGGEST WE COULD BE IN A
RELATIVE LULL AS THE LOW LEVEL JET DIURNALLY WEAKENS AND THE
DISTURBANCE MOVES AWAY. HAVE LEFT A VCSH DESCRIPTOR AT THE TAF
SITES FOR LOW CHANCES FOR SHOWERS OR A STORM.

FOR TONIGHT...ANOTHER EMBEDDED DISTURBANCE IS FORECAST TO ROTATE
SOUTHEAST INTO THE REGION. THERE CONTINUES TO BE DIFFERENCES IN
THE EVOLUTION OF NOCTURNAL CONVECTION. RIGHT NOW..THE BEST CHANCE
FOR SHOWERS/STORMS SHOULD OCCUR AFTER 06Z AND BE MORE WEIGHTED
TOWARDS THE NORTHERN TAF SITES OF KDAY...KCMH...AND KLCK.
HOWEVER...IT SHOULD BE NOTED THAT SOME MODELS HAVE CONVECTION
AFFECTING THE ENTIRE REGION IN THE FORM OF A MESOSCALE CONVECTIVE
SYSTEM. WILL CONTINUE TO MONITOR MODEL TRENDS FOR TIMING AND
SPATIAL COVERAGE.

OUTLOOK...THUNDERSTORMS POSSIBLE FRIDAY EVENING THROUGH SUNDAY.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.

&&

$$
SYNOPSIS...SITES/SNYDER
NEAR TERM...NOVAK
SHORT TERM...SITES
LONG TERM...BINAU
AVIATION...HICKMAN






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