Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 260006

Area Forecast Discussion
National Weather Service Wilmington OH
806 PM EDT Sun Sep 25 2016

High pressure centered northeast of the area has provided another
day of dry and warm weather for the region. A cold front will move
into the area Monday morning, bringing a chance of precipitation.
Behind this front, temperatures will become cooler for the rest of
the week, and will be slightly below normal for late September.


A broad area of high pressure extending down into the northeastern
United States will slowly slide east as an upper level low currently
over the midwest pushes east. As this occurs weak ridging over the
western United States will setup allowing the low to dive southeast.
This will help to push a surface cold front into our western zones
between 10 and 12z. Lows ahead of the front will only fall into the
mid 60s with upper 50s possible across the far northeastern zones.


The cold front will then clear the CWA between 18 and 21z Monday
afternoon. Confidence with the timing of the front remains high
while coverage of precipitation is a little more uncertain. PWATS
are currently around 1.30" (90th percentile for this time of year)
but instability is paltry ahead of the front. ML Cape on the GFS
forecast soundings is less than 500 J/kg in most places while the
NAM has ML Cape values around 500 to 1000 J/kg. Given the frontal
passage is expected mostly in the morning (except for Scioto and
other eastern counties) instability should be limited. Lift will
come from the front but even then saturated equivalent potential
temperature lines don`t really compact until the front reaches
our eastern zones. The given above would support weak showers with
a possible rumble of thunder across our western zones with a line
strengthening as it exits our CWA. High res models are in general
agreement with this solution. The 850 mb frontal passage lags the
surface frontal passage and is more aligned with the better PVA.
The WRF dart and NSSL WRF show this as some weak showers behind
the precipitation associated with the cold front.

Monday afternoon behind the front strong cold air advection and 20
to 25 kt winds will start to mix down. Both NAM and GFS soundings
are supporting wind gusts of around 20 mph via momentum transfer.
The better chance for breezy winds will be across the northwest
which will likely see the CAA during most of the diurnal cycle.
Across our far southeastern counties highs approaching 80 degrees
will be possible with temperatures holding steady or falling
behind the front. Have continued to advertise a non- diurnal curve
for Monday.

The vertically stacked low will continue to mature and occlude
Monday into Tuesday with a tight low level gradient keeping winds
breezy. Mixing will also be greater Tuesday with forecast soundings
showing mixing up 800 mb possible. GFS soundings are showing gusts
up to 30 mph possible while the NAM is more in the 25 to 30 mph
range. Tuesday night into Wednesday another wedge of positive
vorticity will rotate south bringing increasing clouds and
moisture back to the area.


A closed upper level low will settle down across Upper Ohio Valley
region through the end of the work week. The 12Z GFS has trended a
little more in line with the ECMWF with this feature, now hanging it
back across our region through Friday before trying to push it off
to the east over the weekend. Meanwhile the 12Z ECMWF hangs on to
the low even longer, keeping it in place across our area through the
weekend. As a result, will go ahead and allow for some low chance
pops through at least Friday and will try to show at least a little
bit of a diurnal enhancement in the pops. Will also nudge up sky
cover through the afternoons to allow for some diurnal type cloud
development. If the forecast continues to trend toward what the
ECMWF is indicating, pops may need to eventually be added to next
weekend too.

Temperatures through mid week will be a bit below normal with highs
in the 65-70 degree range Wednesday and Thursday. Will then allow
for a gradual warmup with highs into the low to mid 70s through the
weekend, but this may be on the warm side if the low does end up
hanging back.


Sharp upper level ridge over the region ahead of a trof moving
through the northern plains will keep most of the night VFR.

The upper level trof will progress east into the Great Lakes
Monday. Conditions will start to deteriorate late tonight with
the approach of a cold front from the west. Low and mid clouds
will increase after midnight, with a few showers possible toward

Showers with MVFR ceilings are likely to affect all TAF sites
starting around 12z. Have continued to keep thunder out of the
forecast with low instability and isold nature of any potential
convection. With the passage of the cold front winds will shift to
the west and gust up to 25 kts.

The system is progressive and showers will end by afternoon with
skies clearing late in the day.

OUTLOOK...Breezy west winds expected on Tuesday with gusts
between 25 and 30 knots.




NEAR TERM...Haines
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