Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 191750
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
ISSUED BY NATIONAL WEATHER SERVICE LOUISVILLE KY
1250 PM CDT Tue Aug 19 2014

.UPDATE...
Issued at 1250 PM CDT TUE AUG 19 2014

The AVIATION section has been updated for the 18Z TAF issuance.

UPDATE Issued at 1121 AM CDT TUE AUG 19 2014

The fog and low clouds have dissipate, leaving behind just a
scattered cu deck late this morning.

An area of convection has weakened significantly since 15Z as it
moved eastward into the KSTL area. However, it did push an outflow
boundary eastward and it is only a county or so northwest of our
area as of 16Z. Not sure whether the boundary will survive as it
moves into the strong mixing in our region or not, but figure it
or just a differential heating boundary may focus thunderstorm
development possibly by 18Z in the KMVN and KMDH areas.

The latest HRRR and 12Z NAM runs develop convection over much of
southern Illinois and push it southeast through southwest Indiana
and much of west Kentucky through the late afternoon and early
evening hours. The southwestward extent of development is in doubt
due to a very strong capping inversion noted on the 12Z KSGF RAOB.

The forecast has been updated to account for these convective
trends. Capped PoPs in the northeast at 50% due to the potential
for the cap to hold even up there. Also, kept a slight chance in
the far west just in case the cap does not hold. The NAM soundings
indicate that there will be some fairly steep mid-level lapse
rates for storms to feed on, if the cap can be broken. Wind fields
will be increasing, but the best winds may lag the convection
through the area. Given the instability alone, figure that a few
storms will reach severe criteria with winds and hail the primary
concerns.

&&

.SHORT TERM...(Today through Thursday night)
Issued at 214 AM CDT TUE AUG 19 2014

Short term weather continues to be somewhat active.

Aside from patchy/areas of dense fog early this morning, only a few
high clouds are expected to track across the region. An MCS located
over north central Kansas at the time of this writing should weaken
considerably on its southeast trek, and should there be anything
left of it later this morning, it should pass by to our south and
west.

Precipitation chances are expected to make their way into the
forecast this afternoon as a short wave pushes a weak cold front
toward the lower Ohio valley. Due to lack of deeper moisture models
not showing much in the way of convection before 18Z, but after that
precipitation chances should begin to increase from the northwest
with the approach of the aforementioned boundary. With decent flow
aloft over a moderately unstable airmass in place, a few storms
could become strong to severe Tuesday afternoon into the evening
hours, especially over most of southern Illinois and northwest
Kentucky, and all of southwest Indiana. Large hail and damaging
winds will be the primary threats.

Models show the short wave outrunning the surface boundary late
Tuesday night, and with H5 heights beginning to increase at that
point, the boundary never quite makes it into our CWA and gets
pushed back to the north and east as a warm front.

Precipitation chances will begin to diminish from southwest to
northeast on Wednesday as an upper ridge over the southern plains
begins to build northeast across our region . This trend will
continue through Thursday as the ridge continues to overspread the
area. At this time it looks like Thursday night will be dry as the
upper ridge takes control.

Unfortunately with the approach of the ridge, the resultant
compression/warming of the air will raise temperatures to near
normal levels (mid 90s) the latter half of the short term period.
This combined with dewpoints around 70 degrees will produce heat
indices near the century mark for most if not all of our CWA both
Wednesday and Thursday afternoon.

.LONG TERM...(Friday through Monday)
Issued at 214 AM CDT TUE AUG 19 2014

The long term will be dominated by an upper level ridge over the
Lower and Middle Mississippi Valley. This will help to stabilize the
atmosphere as the tropospheric profile undergoes a drying trend.
Consequently, any slight chance for showers and thunderstorms will
likely be shunted north and east of the immediate forecast area
through the weekend.

The main concern during this time will be the heat and humidity as
the hottest weather of the year takes hold. Highs in the mid to
upper 90s will combine with relatively high humidity to push heat
index readings to the 100 to 105 degree range each afternoon. Given
the anticipated prolonged nature of this event, I see little reason
why a Heat Advisory will not be issued later this week for peak
afternoon heat indices between 100 and 105 for at least four
consecutive days. Will continue to monitor and adjust forecast as
necessary.

&&

.AVIATION...
Issued at 1250 PM CDT TUE AUG 19 2014

An outflow boundary is expected to provide a focus for
thunderstorm development over southern Illinois this afternoon.
Best guess is that the storms would impact KEVV and KOWB around
00Z. With plentiful low-level moisture, fog development will be
possible again tonight, but with some southwest wind expected,
LIFR/VLIFR conditions are less likely. If they occur it would most
likely be at KCGI. Just a few cu expected by midday Wednesday,
along with modest west southwest to west winds.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
MO...NONE.
IN...NONE.
KY...NONE.
&&

$$

UPDATE...DRS
SHORT TERM...JP
LONG TERM...RJP
AVIATION...DRS






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