Area Forecast Discussion
Issued by NWS Paducah, KY
FXUS63 KPAH 180252
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
951 PM CDT Sun Aug 17 2014
Issued at 951 PM CDT SUN AUG 17 2014
The grids have been updated with the latest short term guidance now
that all measurable pcpn has left the PAH forecast area. By around
midnight, the low pressure system will be far enough ewd to drop
PoPs below the "mention" threshold. Clouds are likely to continue to
form overnight, especially in the nrn half of the region. This will
be a limiting factor for dense fog after midnight, though it cannot
be ruled out in isold areas. Winds should go pretty close to calm,
and with the recent rains, some vsby restrictions due to fog should
still occur overnight, especially in srn IL east of I-57.
.SHORT TERM...(Tonight through Tuesday night)
Issued at 307 PM CDT SUN AUG 17 2014
The upper-level storm system moving along I-64 this afternoon will
continue to support numerous showers over the Evansville Tri
State through sunset, while more scattered showers and a few
storms move eastward through the Pennyrile region of west
Kentucky. Some showers are likely to be hanging around southwest
Indiana and northwest Kentucky into the evening, but the
thunderstorms in the southeast should be out of the area by then.
Satellite imagery reveals that a large area of stratocu are
spreading south and east on the backside of the low-level
circulation. As the low exits the area, these clouds should spill
across most of the region this evening. Guidance shows this cloud
layer scattering out overnight and dense fog or very low ceilings
developing over much of the region by daybreak Monday. If the
stratocu prevail through the night the low clouds will likely not
develop. Will keep the forecast mostly cloudy and not mention fog
at this time.
Most of the 12Z models develop some isolated to widely scattered
diurnal convection mainly in the southeast Monday, and that seems
reasonable with the heat and humidity across the region. May have
a few showers or storms linger into Monday evening.
As a storm system drops into the western Great Lakes region Monday
night, some convection may make a run at our northern counties
late in the period. As the tail end of the trough aloft moves through
the region Tuesday, at least scattered convection is expected.
Given the rather extreme heat and humidity expected, and
increasing flow in the middle and upper levels, figure that a few
storms could pulse up to near severe levels in the afternoon. Heat
indices may top 100 over the southwest half of the area Tuesday.
Will give this a mention in the HWO.
A few showers or storms may develop in the vicinity of a warm
front that is expected to lift northeast into the region Tuesday
The consensus of available guidance may be a bit hot for highs
Monday and Tuesday, so decided to undercut it a bit mainly in the
northeast. The consensus should be pretty close for lows.
.LONG TERM...(Wednesday through Monday Night)
Issued at 307 PM CDT SUN AUG 17 2014
The middle and upper level high pressure center, effectively
anchored over Central Mississippi over the extended forecast period
will be the dominant weather maker for the area.
Initially, where the thermal cap remains the weakest (Southeast IL,
Southwest IN, and northwest Kentucky) Wednesday into Thursday
afternoon and evening, small PoPs were left to handle diurnal
convection. As the ridge continues to build in and become
established a subsidence inversion will work to limit convection
going into the weekend and early next week.
Given the antecedent moisture from rain and a relatively moist
boundary layer, heat index values will become an increasing concern
early in the extended period. At this time, Wednesday afternoon will
see the greatest likelihood of heat index values approaching 105
degrees. The vast majority of these elevated heat index values will
be along the counties bordering the Ohio and Mississippi Rivers, as
well as the Southeast Missouri delta region, east to the Land
Between the Lakes in Southwest Kentucky. Will offer a mention in the
Hazardous Weather Outlook to raise awareness this next week.
When blending with numerical forecast guidance, leaned closer the
deterministic GFS for temperatures, winds, and to some degree,
dewpoints with the extended forecast package.
Issued at 610 PM CDT SUN AUG 17 2014
Upper Low`s departure will see showers/storms ending early,
followed by clearing that should be short-lived, as winds
diminish, vsbys will become restricted in developing fog. This
will combine with low cigs for a late night-early tmrw morning
flight hazard, with improving daytime conditions.