FXUS63 KPAH 171137

Area Forecast Discussion
National Weather Service Paducah KY
637 AM CDT Tue Jul 17 2018

Issued at 637 AM CDT Tue Jul 17 2018

The AVIATION section has been updated for the 12Z TAF issuance.


.SHORT TERM...(Today through Thursday night)
Issued at 308 AM CDT Tue Jul 17 2018

A few showers and storms continue over the southern Pennyrile as
of 0800Z, but they should continue to push out of the region by
sunrise. Elsewhere skies have become mostly clear, and winds
remain mostly calm. This has resulted in some fog formation over
southern Illinois. Sub 70 degree dewpoints are still north of I-70
and north winds are just north of our southern Illinois counties.
Guidance continues to indicate an uptick in northerly wind by
sunrise, especially in the north, which would keep the fog in
check. We will continue to monitor for any dense fog formation.

The 00Z guidance is holding onto higher dewpoints across much of
the region today, and likewise, is a bit warmer. Much of the area
is likely to see highs around 90 with a few locations possibly
reaching 93 to 94 over SEMO and the Purchase Area. Heat indices in
those regions are forecast to top out around 100, but if these
trends continue, a few places may reach 105. Will address this in
the HWO only for now and let the day shift monitor observational
trends mainly in dewpoints before issuing a Special Weather
Statement. An isolated shower or storm cannot be ruled out this
afternoon over west Kentucky, mainly near the TN border. If the
warmer, more moist trends verify, convective coverage may be
greater and farther north. For now the forecast remains dry.

As surface high pressure finally builds over the region tonight,
we should finally dry out through Wednesday. There is just the
slightest chance of convection forecast in western portions of
Ripley and Carter counties in Missouri Wednesday afternoon, but
the focus for diurnal development will likely be west and
southwest of the area.

Northwest flow aloft will begin to increase over Missouri
Wednesday night into Thursday. The 00Z GFS and ECMWF push some
convection southeast into SEMO late Wednesday night and Thursday
morning. Will have some small chances for this possibility.
Thursday afternoon and evening are expected to be dry, with winds
becoming southeast throughout the area.

A significant storm system will shift eastward from Minnesota
through Wisconsin Thursday night. The GFS and ECMWF both bring
some QPF into our region, as the northwest flow aloft increases.
Will have 20-40% PoPs for this possibility. It should be a mild
night outside of precipitation with persistent south winds and
increasing clouds. Lows should be back into the lower 70s over
most of the region.

.LONG TERM...(Friday through Monday)
Issued at 308 AM CDT Tue Jul 17 2018

Models are in decent agreement through 00z Monday.

Starting at 12Z Friday, the upper air pattern has a large ridge near
the four corners area of the SW US and a weaker ridge along the
eastern seaboard. An upper level low over Wisconsin (which is
currently over Washington State) and another moving into the western
coast of Canada.

The upper level low over Wisconsin will be the big weather maker
early in the period. All models bring a jet streak down across the
central plains to near the lower Ohio Valley by 00Z Saturday. This
jet, along with the upper level low will increase the shear across
the area on Friday into Saturday. Models forecast SBCAPE values of 3-
4K during the afternoon on Friday. A surface cold front will aid in
producing lift. This could be a set up for severe weather.

The NAEFS integrated water transport indicates an area of higher
than normal transport Friday night which may aid in locally heavy

By Sunday, the upper level low moves southeast to the Michigan/Ohio
area. At the surface, high pressure moves in and keeps the area
generally dry through Monday. Tuesday should start to see return
flow on the back side of the high bringing a chance of precip into
southeast Missouri on Tuesday.

Heat wise, Friday may see heat index values at or just above 105
over parts of southeast Missouri and small portions of southern
Illinois prior to thunderstorm development. The high pressure over
the weekend will bring in another shot of mid to upper 60s dew
points for Sunday and Monday.


Issued at 637 AM CDT Tue Jul 17 2018

The TAFs are VFR. Northerly winds under 10kts will mix down by
mid-morning and eventually spread drier air over the region. A
nice cu field is expected by late morning, especially at KCGI and
KPAH. The drier air should prevent fog formation tonight despite
the temperature at most locations dropping below the cross-over
temperature. An isolated SHRA/TSRA cannot be completely ruled out
along the KY/TN border this afternoon.




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