-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 270538
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
138 AM EDT Tue Sep 27 2016

.SYNOPSIS...
A cold front has pushed through the forecast area this afternoon
with cooler and drier weather behind it. An upper level low
pressure system is expected to move into the Great Lakes and Ohio
Valley by mid week which will keep the weather cool due to clouds
and the threat for showers.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
In the wake of surface cold front, skies have cleared from west to
east this evening. A few clouds remain in the far southeast
counties but this clearing trend will continue with clear skies
persisting through the overnight hours. Much drier and cool
airmass to advect in on west to southwest winds. Surface dewpoints
which were in the lower/middle 60s this morning, will drop through
the 40s overnight. Low temperatures are expected to be in the
middle and upper 40s by sunrise. These readings will be around 5
degrees below normal.


Previous Discussion...
The surface cold front has cleared the CWA with only some light
rain occurring across our eastern zones. Drier and cooler
conditions will then move in behind the front. The clearing line
should move through the forecast area this afternoon into evening.
Tuesday morning behind the front much cooler air will work into
the area with lows in the mid to upper 40s expected.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/...
Tuesday a vertically stacked upper level low will start to drift
south keeping the low level gradient tight. Clear skies will also
promote deep mixing (~800 mb) which will allow winds to breezy at
times. Both GFS and NAM forecast soundings are indicating wind
gusts up to 30 mph possible at times (via momentum transfer) and
sustained winds of 15 to 20 mph. Current wind and wind gust grids
looked good so have made only minor changes here. Afternoon highs
Tuesday will also reach in to the lower 70s as 850 mb
temperatures hover just under 10 degrees C and 1000/850 mb
thicknesses fall to 1375 m.

Tuesday night into Wednesday morning the upper level low will
continue to drift south allowing PWATs to rise from under 0.40"
back up to just under 1.00" in places. By late Wednesday afternoon
the upper level low will be just north of the forecast area
bringing clouds and the chance of rain back to the area. Forecast
soundings on both the GFS and NAM also show some weak instability
Wednesday afternoon towards the south. Given the instability and
upper level lift can`t rule out a couple of strikes of lightning.

Wednesday night into Thursday the upper level low will pinch off
from the main flow and remain quasi-stationary over the Ohio
valley. The GFS, CMC, ECMWF, and UKMET have all come into pretty
good agreement with this. In general, this would support chance
showers and isolated thunderstorms with a smaller diurnal range
every day. Have lowered max temps a bit to account for this.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The GFS has continued to trend more in line with the ECMWF,
lingering the upper level low across the region through at least the
end of the week. As a result, have continued to nudge up pops each
day through Saturday and tweaked down temperatures a bit. Beyond
that, both the GFS and ECMWF are trying to lift the low
northeastward and out of the area, although the ECMWF is still
slower in that process. At this point, will keep Sunday and Monday
dry but again, if things continue to trend toward the slower ECMWF,
we may need to introduce some low end pops into early next week and
lower temperatures a bit more toward the end of the long term
period.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Skies will remain clear with light winds from the south/southwest
through sunrise.

Otherwise, our region will find itself between a departing cold
front to our east and a large scale upper level low dropping south
into the western Great Lakes today. An increasing pressure
gradient, combined with fairly decent diurnal mixing, will allow
winds to increase and become gusty from the west/southwest
between 15Z and 17Z. Wind gusts will range between 20 and 28
knots with the highest gusts expected at KDAY. At the same time,
models indicate a subtle moisture channel in the low levels, which
should result in a few high based diurnal cumulus clouds by 17Z.

For tonight, some scattered cirrus can be expected through early
morning. Upper level low pressure will continue to move toward the
southeast. Models indicate that a cold front will begin developing
to our west. The combination of this approaching front and dynamic
lift associated with energy rotating around the upper level low
will cause clouds to increase/thicken between 09Z and 12Z with a
few showers possibly developing toward the end of the 30 hour TAF
period.

OUTLOOK...MVFR ceilings and visibilities possible with showers on
Wednesday. Widespread MVFR ceilings with local MVFR visibilities
possible with showers Thursday through Saturday.

&&

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

&&

$$
SYNOPSIS...Haines
NEAR TERM...Haines/AR
SHORT TERM...Haines
LONG TERM...JGL
AVIATION...Hickman