Area Forecast Discussion
Issued by NWS Paducah, KY

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031
FXUS63 KPAH 241730
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1230 PM CDT Wed May 24 2017

.UPDATE...
Updated aviation section for 18z taf issuance.

&&

.SHORT TERM...(Today through Friday night)
Issued at 305 AM CDT Wed May 24 2017

A deep closed 500 mb low will drop almost due southward across
Missouri today, reaching northeast Arkansas by this evening. There
is an unusually large amount of clear sky and dry air associated
with this low. The forecast for today only contains chance pops
(scattered showers) for southeast Missouri and southwest
Illinois. Intervals of sunshine are likely there, which may
initiate a few isolated afternoon thunderstorms due to the cold
core with the upper low (minus 20 at 500 mb).

The more important feature for west KY and southwest IN is a 500
mb shortwave over the Arklatex region early this morning. This
shortwave will lift northeast ahead of the parent upper low. This
shortwave is responsible for a rain shield that extended from the
Lower Mississippi Valley into the Lower Ohio Valley early this
morning. The rain will persist across southwest Indiana and parts
of west Kentucky until the passage of the shortwave, which will be
sometime early this afternoon. High temps today will be in the
60`s in all areas due to cool northwest winds on the back side of
a surface low, which will track from middle Tennessee to eastern
Kentucky.

The upper low will move east tonight, reaching central Kentucky by
morning. A dry west to northwest flow tonight will result in
partial clearing for many areas. The primary exception is
southwest Indiana and northwest Kentucky, where a band of rain
possibly associated with the deformation zone of the 500 mb low
could last much of the night.

On Thursday, 500 mb heights will rise rather quickly in the wake
of the departing upper-level low. Some light rain may linger
across southwest IN and Pennyrile region of west KY early in the
day, but the 00z models are a little faster moving the rain out.
Model soundings indicate low-level moisture will be problematic
for cumulus development. Both the gfs and nam soundings suggest a
lot of high-based shallow cumulus clouds through the day,
especially north and east of kpah. Highs will range from the upper
60`s under the cloudiest areas east of kevv to the mid 70`s in the
sunnier areas of se Missouri.

On Friday and Friday night, deep southwest flow will increase
ahead of a broad 500 mb trough moving into the northern Plains.
This will result in increasing clouds and warmer temps Friday,
with highs in the lower 80`s. Strong low-level advection of warm
moist air will produce abundant clouds and possibly elevated
showers or storms Friday night. The proximity of weak 500 mb
ridging over the Gulf coast states and Tennessee Valley should
limit precip chances to the chance category.

.LONG TERM...(Saturday through Tuesday)
Issued at 305 AM CDT Wed May 24 2017

Forecast confidence is moderate to high throughout the extended
portion of this forecast with general agreement amongst the 00Z runs
of the medium range models.

Our weather will be dominated by a sprawling upper-level low
pressure center that will move slowly eastward from the Canadian
Prairies early Saturday into Ontario by Sunday and then farther east
into next week. At the surface, a cold front will push slowly east
through the region Saturday night into Sunday morning.

We will see widely scattered showers and thunderstorms in the warm
sector Saturday and then better coverage of convection near the
front Saturday night and Sunday. A few strong to severe storms
cannot be ruled out along and ahead of the front, but the primary
concerns will be locally heavy rainfall and lightning.

An upper-level impulse will rotate around the backside of the main
upper low and through our region Monday night into Tuesday. It
should push a weak surface trough through as well, and some isolated
convection will be possible mainly over the northern and eastern
portions of the region. A final disturbance may bring some isolated
convection to the EVV Tri State area Wednesday. It will be difficult
enough to get thunder Monday night through Wednesday, so severe
weather is not anticipated.

Temperatures will generally trend downward through the period.
Starting out a few degrees above normal Saturday and dropping to a
degree or two below normal by next Wednesday.

&&

.AVIATION...
Issued at 1220 PM CDT Wed May 24 2017

With this 18z Wednesday WFO PAH routine TAF package, kept IFR
ceilings and MVFR/IFR visibilities in KEVV/KOWB due to clouds and
banded rainfall rotating north ahead of a shortwave rotating east
of a closed low as it dives south into western sections of
southeast Missouri. Added a mention of vicinity showers to
KCGI/KPAH to address instability-based convection with the upper
low during peak heating.

For the late afternoon and evening improved conditions to VFR for
the WFO PAH TAF locations to reflect contraction of weather and
eastward movement of the upper low.

However, kept lower ceilings and visibilities overnight, as lift
associated with the upper low generates some drizzle at KCGI/KPAH
and IFR/MVFR ceilings at KEVV/KOWB through Thursday morning.

&&

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

$$

SHORT TERM...MY
LONG TERM...DRS
AVIATION...Smith



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