Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 270456
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1156 PM CDT TUE JUL 26 2016

.UPDATE...
Issued at 1156 PM CDT TUE JUL 26 2016

Updated aviation discussion only.

&&

.SHORT TERM...(Tonight through Thursday night)
Issued at 244 PM CDT Tue Jul 26 2016

Thunderstorms developed on queue around 17z as surface temps
reached the convective temp near 90. Through early afternoon, most
of the development has been near a surface boundary extending from
kevv/kowb west-southwest across kcgi to the Ozark foothills.

The boundary is forecast to sag south through this evening into
the very unstable air mass over southwest Kentucky. Very heavy
rain will continue to be the main hazard. Precip water values are
forecast to remain well above seasonal climo values. Some model
runs have been showing pwat values near 2.5 inches moving northward
across Tennessee this week. This is in the 99th percentile for
this time of year, based on kbna sounding climatology.

Compared to last night, coverage of showers and storms may be a
little higher tonight due to stronger upper support. The rap/nam
both indicate a weak but sharpening 500 mb trough just upstream
of our region late tonight. Regardless of coverage, a decrease in
intensity is expected as the atmosphere stabilizes overnight.

On Wednesday, the proximity of the weak upper trough and the
lingering low-level boundary should result in fairly good
coverage of storms. The activity should be strongly influenced by
diurnal heating, so pops will be significantly higher in the
afternoon. Highs will again be in the neighborhood of 90, which is
about the convective temp.

Wednesday night and Thursday, the models continue to indicate
surface low pressure taking shape over the Upper Midwest/Great
Lakes. This is in response to a relatively strong 500 mb shortwave
moving southeast from the Upper Mississippi Valley. This should
result in our best precip coverage of the week as the trailing
cold front approaches. Again, the potential for localized heavy
rain is quite high given climatologically high precip water
values over 2 inches. Pops will be in the likely category for
Thursday. Temps will be moderated by clouds and rainfall, with
highs in the 80s and lows in the 70s.

.LONG TERM...(Friday through Tuesday)
Issued at 244 PM CDT Tue Jul 26 2016

Continued average confidence in the long term due to model
differences.

Very few synoptic changes in the long term, especially through the
upcoming weekend. Through most of the long term period our region
remains under a broad H5 trough with models bringing a weak cold
front into or just north of our CWA, depending on which model you
believe. During the same period models bring a series of upper level
disturbances through the trough. The combination of the proximity of
the surface boundary, plenty of moisture/instability in place, and
upper level forcing for ascent should generate scattered showers and
thunderstorms every period, especially during the daytime hours.

Previous model runs were trying to build the upper ridge eastward
back across our region by the first of next week but latest runs
have backed off on that solution keeping us on the back side of the
H5 trough, thus keeping precipitation chances across the area
through the end of the period.

Temperatures should remain at to just below normal through the
period, so we`re not expecting any heat headlines, but with
dewpoints remaining in the 70s, humid/sticky conditions will
continue.

&&

.AVIATION...
Issued at 1156 PM CDT Tue Jul 26 2016

Rainfall and its vsby restrictions will be unlikely overnight at the
TAF sites as the trop stabilizes. However, fog and some low clouds
will be present, producing at least MVFR vsbys primarily after
midnight. Where substantial rain occurred today (KCGI) LIFR vsbys
and even LIFR cigs are possible late tonight. Winds will be
generally on the light side and quite variable. Scattered showers
and tstms should develop by mid afternoon Wed. Vsby restrictions at
the terminals associated with showers and tstms were not included,
but brief reductions to IFR are not out of the question.

&&

.PAH Watches/Warnings/Advisories...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

SHORT TERM...MY
LONG TERM...JP
AVIATION...DB



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