Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Paducah Kentucky
825 am CDT Sat Jul 23 2016
issued at 825 am CDT Sat Jul 23 2016
Revised grids, text, and tabular forecast package to reflect the
cancellation of the dense fog advisory. A revised npw was also
issued to reflect the latest version of the excessive heat warning
and heat advisory, without the dense fog advisory.
Short term...(today through Monday night)
issued at 328 am CDT Sat Jul 23 2016
Both the high resolution short range and coarser medium range
guidance suggesting the greatest eastward expansion of the ridge
axis and accompanying subsidence and capping lid for widespread
convection spreading across most of the weather forecast office pah forecast area
through Sunday. The ridge weakens and separates over the weather forecast office pah
forecast area very late Sunday night into Monday as the
westerlies, aided by a sharpening progressive trough over the
Great Lakes. This will suppress the ridge and allows sharper
lapse rates and upward lift to move into the area, allowing at
least scattered, diurnal convective activity.
Some evidence of the influence of the ridge is the observations of
dense fog at reporting sites over southeast Illinois. Although
there has been some variability in the range of visibilities at
any one location (from 1/2 mile to 3 miles at times), the overall
trend has been downward overnight. Anticipate the greatest
visibility reduction over a larger area overnight (this Saturday
morning) will range between 4 am and 7 am CDT. Any fog will delay
heating slightly through 9 am CDT, but the pool of moisture and
insolation will still allow heat index values to rise sufficiently
during the afternoon.
Plan to keep the excessive heat warning and heat advisory in place
through its natural expiration time this Sunday at 8 PM CDT. The
main convection for today will most likely be confined to west
Kentucky (pennyrile region) this Saturday, with low pops over the
northwest and southeast third of the weather forecast office pah forecast area for the
afternoon hours on Sunday. Analysis of forecast heat index
gridded values, suggest that southeast Missouri will have the
greatest chance of seeing heat index values approach 105-110,
with the remainder of the area between 100-105 today and Sunday
(outside of areas where rain is forecast to fall).
Long term...(tuesday through friday)
issued at 328 am CDT Sat Jul 23 2016
The medium range models are in reasonable agreement in developing a
weakness in the ridge aloft right over our region for much of next
week. This will be a gradual process, so a very minor cooling trend
is forecast through the week. We still will be within a degree or
two of normal on Friday.
Of greater concern though is a weak surface boundary that will be
meandering across the region through the week. As relatively weak
upper-level disturbances stream eastward across the region, periods
of showers and thunderstorms are likely to develop near the boundary
and progress eastward across the area. We will not be lacking for low-
level moisture, so heavy rainfall is likely. Flooding problems will
become more of a concern with each passing round of thunderstorms
through the week. A cluster of strong to severe storms cannot be
ruled out for the last half of the week, as the flow aloft improves
issued at 639 am CDT Sat Jul 23 2016
Intermittent patchy ground fog interspersed with broader layer fog
at kcgi and kpah, with kevv experiencing MVFR conditions during
the same time period. The impact of surface ridge becomes more
pronounced across the weather forecast office pah taf locations with light winds and
diurnal cumulus expected with this forecast package. A mention of
vicinity showers was entered for the middle afternoon hours at
kcgi/kpah...otherwise no concerns for convective activity at the
remaining sites this afternoon and evening.
Illinois...excessive heat warning until 8 PM CDT Sunday for ilz075>078-
MO...excessive heat warning until 8 PM CDT Sunday for moz076-086-087-
In...heat advisory until 8 PM CDT Sunday for inz081-082-085>088.
Kentucky...excessive heat warning until 8 PM CDT Sunday for kyz001>009.
Heat advisory until 8 PM CDT Sunday for kyz010>022.