Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 271725 AAA
AFDPAH

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PADUCAH KY
1225 PM CDT Wed Aug 27 2014

.UPDATE...
Issued at 1225 PM CDT WED AUG 27 2014

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

&&

.SHORT TERM...(Today through Friday)
Issued at 323 AM CDT WED AUG 27 2014

The Heat Advisory looks good for today. Yesterday we once again
underestimated the temperatures and especially the dewpoints. Went
with the highest dewpoints I could find in the available guidance
and increased them just a bit through the day. Also, went a degree
or so above the consensus of guidance for highs this afternoon. It
all boils down to 100-105 in most locations, which will satisfy
the 4+ day criteria for Heat Advisory issuance.

Convection today is supposed to be focused along a weak back-door
cold front that has been forecast to enter the area from the north
this afternoon. The boundary has become harder and harder to find
in the model wind fields and the model QPF has become less
coherent over the last day or so.

The front appears to be located along the Iowa/Missouri border and
eastward through Illinois into northern Indiana as of 0730Z. Short
term guidance brings it down near Highway 13 by late this afternoon.
Will focus low chance PoPs along and north of the Shawnee Hills in
southern Illinois, and eastward through northwest Kentucky and
southwest Indiana. Could also see some isolated to widely
scattered convection in the higher terrain in southeast Missouri.
Figure that the convection will be diurnally based, so would not
expect anything past sunset.

Thursday will be an interesting day across the area. The front is
likely to become stationary from southern Illinois into west
Kentucky early Thursday, but it will likely become even more
diffuse through the day. Would expect moisture to pool in the
vicinity of the boundary, and scattered afternoon convection seems
reasonable with the greatest coverage expected across southern
Illinois.

In the absence of convection or convective debris, temperatures
are likely to climb well into the 90s on Thursday. Figure most
areas will achieve most of their potential warming prior to the
onset of convection, so with dewpoints likely to remain well into
the 70s through the day, heat indices may climb above 100 degrees
once again, especially over west Kentucky and the Missouri Boot-
heel. However, given the uncertainties in the convective forecast,
it is too difficult to determine how much of the area may need a
continuation of the Heat Advisory.

The 00Z models are not sure what they want to do with convection
for Thursday night. Would not be at all surprised to see some at
least isolated convection bounce around areas mainly east of the
Mississippi River through the night, with some weak warm advection
possible in the low-levels.

For Friday, the 00Z NAM is too fast with the arrival of the storm
system moving in from the west. The ECMWF and GFS are in agreement
in keeping any impacts from this system to the west of the area
through Friday. They push whatever is left of the boundary back
to the northeast early Friday, and re-establish the warm sector
over the entire region. Along with this evolution, modest south
southwest low-level flow may finally bring in or mix down drier
air. With plenty of sunshine expected for much of the day,
temperatures will likely climb well into the 90s or well above
guidance. Thankfully, with the dewpoints mixing into the 60s
areawide, heat indices should stay under 100 for the first time in
the last 10 days.

.LONG TERM...(Friday Night through Tuesday)
Issued at 323 AM CDT WED AUG 27 2014

Forecast models remain in fairly good agreement in forecasting the
northeastward progression of a mid level shortwave trough from the
Central Plains into the Great Lakes over the weekend. With the
exception of the NAM, most models keep the bulk of the precipitation
west of the immediate forecast area through Friday evening.

Thereafter, the potential for showers and thunderstorms will be on
the increase Saturday into Saturday night. Not confident as to how
much precipitation will actually be around on Saturday, as multiple
models now indicate the brunt of the initial wave will be deflected
just north of the region. The better chance will likely arrive
Saturday night into Sunday morning as another piece of energy heads
northeast from the Lower Mississippi Valley into the Tennessee
Valley. While a few strong storms cannot be ruled out, the main
concern during this time will be locally heavy rain with deep
unidirectional southwest flow and precipitable water values in the
vicinity of 2 inches.

The presence of abundant clouds and scattered precipitation will
likely keep a lid on daytime temperatures, thus highs in the 80s are
forecast over the weekend. It will remain quite humid though with
lows each morning in the lower 70s. Precipitation chances will
decrease Sunday night through Monday night, but not entirely given
the very warm and humid conditions in place. Temperatures by Monday
and especially Tuesday will be in the neighborhood of the 90 degree
mark once again. Our next precipitation chance arrives Tuesday with
the approach of a cold front--the details of which are sketchy at
this point given poor model agreement.

&&

.AVIATION...
Issued at 1225 PM CDT WED AUG 27 2014

A weak cold front will try to push into the area today. Isolated
to widely scattered afternoon thunderstorms will be possible along
and behind the front. The expected coverage is too low to mention
at this time.

IFR or lower conditions are likely to develop again late tonight
at KCGI and KPAH, but MVFR should be the rule at KEVV and KOWB.

An area of MVFR clouds currently behind the front over northern
Indiana and northeast Illinois may impact KEVV and KOWB late
tonight. For now will just have a scattered deck, but some
guidance hints at the possibility of ceilings. Of course if the
ceilings develop, fog will not be an issue, but MVFR conditions
will still impact the terminals.

Light and variable winds will go calm by sundown, then pick up out
of the east to southeast AOB 5 knots after 15Z.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...HEAT ADVISORY until 7 PM CDT this evening FOR ILZ075>078-080>094.

MO...HEAT ADVISORY until 7 PM CDT this evening FOR MOZ076-086-087-100-
     107>112-114.

IN...HEAT ADVISORY until 7 PM CDT this evening FOR INZ081-082-085>088.

KY...HEAT ADVISORY until 7 PM CDT this evening FOR KYZ001>022.

&&

$$

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





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