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Area forecast discussion 
National Weather Service Wilmington Ohio
805 PM EDT Sat Oct 25 2014

Synopsis...
a cold front shifting through the Ohio Valley is leaving clear
skies in its wake as it passes off to the east this evening. Clear
and cool conditions tonight will be followed a by a brilliantly
sunny Sunday with highs in the 60s and low humidity. A warm
frontal passage Monday morning will bring a return flow of gusty
southerly winds...and temperatures Monday afternoon will soar well
into the 70s...with an outside threat of 80s in Kentucky and
southern Indiana. A strong cold front will shift through on
Tuesday bringing a band of showers and a few thunderstorms along
with it. Most areas will see at least some light to moderate rain
amounts as the front passes.

&&

Near term /until 6 am Sunday morning/...
a cold front is currently analyzed across Ohio into southern
Indiana and pressing east. Broken stratus out ahead of this feature
has just about cleared the forecast area...with nothing but clear
skies all the way to The Rockies. So a pretty straightforward forecast
for tonight. Think there may be some shallow/valley fog in some
areas...but analysis of moisture trends /rap and NAM lowest 100mb
mixing ratios/ suggests drying will really take hold especially after
midnight across ind/OH. Have a little concern in northern Kentucky given sref
visibility probability relative maximum across the southern 1/2 of Kentucky and
GOES synthetic fog product showing potential of fog/stratus
development over much of Kentucky after midnight. So observational
trends will have to be monitored across our south later on evening
for perhaps some inclusion of fog into the forecasts. For low
temperatures - kept very close to the previous forecast with a nudge toward
some internal bias-correction to enhance the warm/cool prone areas
on strong radiational cooling nights.

&&

Short term /6 am Sunday morning through Monday night/...
a delightful Sunday in store as shortwave ridging builds across
the Ohio Valley during the day and surface high pressure crosses
Ohio/Kentucky into WV by Sunday evening. Extremely deep/dry troposphere
is attendant to these features...with lowest 100mb mixing
ratio/dewpoint trends tied very strong to airmass currently seen over
Minnesota/ND where dewpoints have mixed into the upper 20s. Precipitable water forecasts
from various nwp suggest 0.25" which is about 40% of normal. Will
allow dewpoints to mix out in the afternoon into the Lower/Middle 30s
under bright sunshine and light northwesterly boundary layer flow. Will not
be surprised to see dewpoints into the upper 20s in a few
spots...particularly wcntl Ohio/ecntl ind. Weak cold advection especially the first
1/2 of the day keeps maximum temperatures in the 60s. Again...kept temperatures
trended very close to previous forecast which lined up fairly well with
mixing GFS/NAM 925mb temperatures to the surface. A quintessential fall day
in the Ohio Valley.

Sunday night...start to return flow with winds backing to
southerly during the night and not falling off. This should yield
a slightly milder night save for the Scioto valley which will
still be in close enough proximity to the surface high for better
decoupling.

Monday...think rapidly developing warm advection in the lower
troposphere and moisture advection may lead to a band of low/middle
clouds along and in advance of the surface warm front. Brought sky
cover up to the 50-65% range for a few hours as we transition the
synoptic warm front from SW to NE across the area Monday morning.
This should open the door for strong warm advection in the afternoon as low
level flow increases. Boundary layer winds to become gusty /25
miles per hour/ in the afternoon as dewpoints begin to rapidly climb. Some
detailed temperature analysis suggests a run at 80 degrees not out of the
question in the southern/western half of the forecast area. Recent
NAM runs /and continuing on 25.12z NAM/ have been the warmest
suggesting +16c to even +17c 850mb temperatures /2 sigma above climatology/
will be bodily advected into the area by middle afternoon with 925mb
temperatures near +19c. Sounding climatology suggests an 850mb temperature of
+17c on October 27th would be the 2nd warmest 850mb temperature for this
late in the season ever on the iln sounding climatology. That /and
the +2 sigma Standard deviation/ suggests we consider record or
near record high temperatures...especially given sunshine and mixing. But
am going to keep temperatures a few degrees below records maximum temperatures /low
80s at cmh/cvg/day for the following reasons: 1) component of
boundary layer is too southerly for my liking - would like to see
more 240/250 /WSW/ degree wind direction instead of 190/200
degree /SSW/ wind direction 2) big boundary layer moisture
increase with dewpoints rising all day through the 50s - this
decreases low level lapse rates and suggests mixing beyond 900mb
will be unattainable 3)increasing cirrus should filter at least a little
bit of sun 4) arrival of warmest 925mb air is late in the
afternoon -- not in place during the day like further to the SW 5)
925mb temperature climatology suggests the forecast +19c by NAM is not quite as
atypical for this late in the year...and given the 925mb temperature is a
much better proxy to high temperature around per local regression
equations...will halt temperatures from reaching record levels and
instead stop them a couple degrees short...or middle 70s in the north
to near 80 in the far South/West. Previous/recent days with temperature
structure like Monday was October 30th 2009 - cvg hit 80f and cmh
79. This was with an 850mb temperature of +17c. It will be very capped on
Monday so dry forecast and only some high cloud.

With the winds staying up Monday night and a maintenance of the
very warm lower tropospheric warmth mentioned above...will skew
lows way on the warm side of the blended guidance...keeping lows
in the lower 60s. Will hold off on rain mention with the
approaching front into Tuesday /discussed below/.

&&

Long term /Tuesday through Saturday/...
a middle level short wave moving from the northern plains and into the
Great Lakes region will help drive a cold front through the Ohio
Valley Tuesday into Tuesday evening. With good low level moisture
convergence developing out ahead of the front...expect showers to
push in from the northwest Tuesday morning...working into our
southeast through Tuesday afternoon. Will continue with a mention of
thunder across our entire forecast area...but expect the best chance to be
across about the southeast half of our forecast area where some slightly better
instabilities will be pulled up into the area through Tuesday
afternoon. Will also likely see a decent temperature gradient across
our area with highs on Tuesday ranging from the middle/upper 60s
northwest to middle 70s southeast. As the front pushes off to the
east...precipitation will taper off from the northwest Tuesday evening...and
across the southeast through the overnight hours.

Surface high pressure and a cooler airmass will build into the area
Wednesday into Thursday. Expect highs both days only in the middle to
upper 50s. Short wave energy dropping down across the Great Lakes
will then help carve out a deepening trough over the eastern United
States through the end of the week. As this short wave drops down
into our area...expect a chance of showers to develop later Thursday
night and into the day on Friday. This will also be accompanied by a
reinforcing shot of colder air. Temperatures will be well below
normal toward the end of the week with highs on Friday in the upper
40s to lower 50s...cooling into the middle to upper 40s by Saturday. It
also looks like the potential for a fairly widespread freeze later
Friday night into Saturday morning.

&&

Aviation /00z Sunday through Thursday/...
in the wake of a cold front...expect clear skies overnight as
surface high pressure noses in from the west. Drier air is moving in
on west to northwest winds...so generally expect VFR conditions to
prevail. Fog will likely form at kluk valley location where IFR
conditions are expected to develop late. Some MVFR visibility
restrictions are also possible at Kiln. Expect fog to quickly
improve Sunday with VFR conditions at all taf sites.

Outlook...thunderstorms are possible on Tuesday.

&&

Iln watches/warnings/advisories...
Ohio...none.
Kentucky...none.
In...none.

&&

$$
Synopsis...binau
near term...binau
short term...binau
long term...jgl
aviation...Arkansas

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