Area Forecast Discussion
Issued by NWS Wilmington, OH-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KILN 210217
Area Forecast Discussion
National Weather Service Wilmington OH
1017 PM EDT WED JUL 20 2016
-- Changed Discussion --High pressure will extend across the region through Friday. A
weakening front will push through Friday night. The high will
build back in for the weekend with very warm and humid air
remaining in place.
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.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --Cirrus stretching from west-central Indiana to the southern tip
of Ohio is rapidly thinning out, and skies will become clear for
most of the area overnight. At this hour, dewpoints remain muggy
in the lower 70s west of I-75 and will keep temperatures a bit
warmer across our west overnight. Winds will remain calm or very
light out of the SSE. Could see some patchy fog develop in areas
west of I-75 late, but it appears the better potential will be
just west of our forecast area where low level moisture is more
abundant from rainfall over the past 24 hours. Generally nudged
low temps up a degree or so from the previous forecast, though
knocked lows down a tad for counties east of Columbus given lower
dewpoints in place over central Ohio.
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.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Increasing heat and humidity will be the main focus with first
heat headlines of the summer possible for Friday. High pressure
ridge will keep any convection minimal through Friday morning.
Temperatures are certainly heating up along with increasing dew
points. This will lead to Heat indices in the mid and upper 90s
for Thursday and should top out around and just above the 100
degree mark by Friday. Will hold off any heat headlines for now
but continue to mention in HWO. Bigger question mark is amount of
convection for Friday afternoon into Friday night. With weak front
pushing down expect scattered coverage at least for the late
afternoon and evening with diminishing trend through the night
Friday night. Again temps near or just above guidance through
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
At 12Z on Saturday...the ILN forecast area will be situated on the
nern periphery of a massive flat/strong ridge centered from the ern
Pacific all the way across to the mid-atlantic coast. Two
anticyclone centers /~595dm at 500mb/ will anchor this ridge over
Missouri and southern California. Several shortwave troughs will be
found at 12Z in the modestly strong subtropical jet stream atop this
flat ridge...a broad/weak trough crossing sern Canada/New England
and a stronger/sharper trough in Montana.
The story through this entire period will be 1) heat and humidity
and 2) low predictability threats for storms. The impacts will most
definitely be felt on a more widespread basis from heat and
humidity...as everyone will get in on this action. In
particular,Saturday/Sunday will pose the most heat threat although
Monday may be oppressive depending on frontal timing. Impacts from
storms will be fairly typical for mid/late July...expect slow moving
storms with potential for downbursts and localized flooding via
excessive rain rates.
Details/predictability issues...right off the bat there`s a
heat/humidity issue given all global models wanting to slip a weak
front (attendant to southeast Canada/New England shortwave mentioned
above) into Ohio/Indiana. There will be good drying north of this
boundary...and some recent runs /06Z GEFS mean and GFS
deterministic/ blow this boundary all the way into KY suggesting a
respite from oppressive 70+ dwpts. Not buying it -- think recent
20.12z runs of NAM/CMC/ECMWF/GFS showing front hanging up over
northern OH to be more realistic...thus expect heat advisory level
impacts to continue across all but perhaps the far north/east on
Saturday...and for sure into Sunday. Given 925mb temps and blend of
2m Td...seems reasonable to expect low/mid 90s and low/mid 70s dwpts
with heat indices 100-105F most locations. This front will likely
spark isold/sct convection Sat aftn/night given strong instability.
Given expected weakness in tropospheric flow /effective bulk shears
< 20kts both days/ these storms will slow moving...prodigious rain
producers with a higher overall threat for localized flash flooding
and localized downbursts or small periods/swaths of wind damage if
cold pools can merge.
On Sunday night/Monday...the MT shortwave mentioned above should be
crossing to the north of the Great Lakes and will likely be the
impetus for better storm coverage/development but timing is
concerning which may bring better rain chances Sunday night. A
little better flow with the wave may allow for a little better storm
coverage/organization/severity if a Monday frontal passage occurs at
On Tues/Wed...some relief though height falls will be rather modest
and cooling too. Expect temps/dwpts to fall back to more seasonable
summertime values during this time.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Expansive cirrus over Indiana will continue to move southeast
over the terminals through about 04Z. Thereafter, expect mostly
clear skies for the remainder of the overnight. Cannot rule out
some mist at KLUK overnight given dewpoints expected to be in the
upper 60s. With the region still under a high pressure ridge,
winds will remain very light through the TAF period, veering to
the south by daybreak Thursday and southwest by afternoon. Some
daytime cumulus will likely develop again on Thursday.
OUTLOOK...Thunderstorms possible Friday and Sunday into Monday.