Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 220847

Area Forecast Discussion
National Weather Service Paducah KY
347 AM CDT Thu Mar 22 2018

.SHORT TERM...(Today through Saturday night)
Issued at 330 AM CDT Thu Mar 22 2018

Surface ridging from the Great Lakes down the Mississippi River
Valley early this morning will slowly shift east today. This will
keep dry conditions in place through much of the day. Meanwhile,
a weak ripple of energy over the Northern Plains is forecast to
drop southeast through the northwest flow into Mid Mississippi
Valley by day`s end. This will result in an increase in sky cover
this afternoon and even a small chance for showers across northern
portions of southern Illinois and southeast Missouri late in the
afternoon. Given the very dry air in place in the lower levels,
most of what falls should evaporate before reaching the ground.
However, enough could reach the ground to measure a trace or a few
hundredths--thus the small rain chances. This initial wave will
diminish as it shifts east into the Evansville Tri-State area this
evening, but another ripple of energy may bring a chance for light
rain to the western half of the area late tonight.

Meanwhile, a broad scale warm advection pattern will get underway
tonight and Friday as a warm front forms east of low pressure
developing over the Central High Plains. The resultant increase in
moisture and large scale ascent will yield the potential for
showers from Friday through Saturday. A stronger disturbance will
kick the surface low east across Kansas on Friday and Missouri by
Friday night. The development of mainly elevated instability will
also result in a slight chance of thunderstorms across most of the
area late Friday night and Saturday morning. The chance for
showers and perhaps a few thunderstorms will linger into Saturday
afternoon as the surface low drops southeast across the area. At
this time, severe weather does not appear to be much of a concern
given the mostly elevated nature of the convection. Rainfall
totals are still forecast to average around one half inch. Higher
totals in excess of one inch remain possible across the Evansville
Tri-State, while amounts below one quarter inch are expected over
much of southeast Missouri.

Expect about a 10 degree temperature gradient between southwest
Indiana and southeast Missouri today and Friday with highs forecast
between 50 and 60 in most locations. Any temperature drop tonight
will likely be limited by the increase in cloud cover. With the
surface low cutting across the area, temperatures on Saturday will
likely exhibit an even sharper gradient, with a 25 to 30 degree
spread possible between Pike County Indiana and Ripley County
Missouri. Most areas should see highs in the 50s or 60s. Readings
will likely drop back into the 30s in most locations Saturday
night in the wake of the cold frontal passage.

.LONG TERM...(Sunday through Wednesday)
Issued at 330 AM CDT Thu Mar 22 2018

Forecast confidence is above normal Sunday through next Thursday.

The upper flow pattern will become rather amplified and blocky for
much of next week. A ridge will develop over our region over the
weekend and then shift toward the East Coast by Tuesday. This will
leave our region in southwest flow aloft through at least next

Some model differences exist, mainly with the character of a
northern stream trough over southern Canada Wednesday into Thursday.
The 00Z ECMWF keeps a large trough intact and hangs it up over south
central Canada, as the upper ridge holds over the East Coast. The
GFS has multiple smaller-scale troughs that are more progressive and
flatten the upper ridge. The Canadian model seems to be in between.
Given the amplified, blocky nature of the flow, the ECMWF is favored
this morning.

Sunday will be dry with high pressure at the surface and aloft. As
energy drops south into the Desert Southwest, the upper ridge will
build east of the area allowing southwest flow to commence Sunday
night into Monday. At the surface, lee cyclogenesis will get going
in the central High Plains. This will push a warm front through our
region late Sunday night into Monday along with scattered to
numerous showers and thunderstorms. The Gulf of Mexico will also
open up, allowing for significant northward transport of low-level

Persistent southwest flow aloft and a wide open Gulf will lead to
heavy rainfall near the primary surface cold front, which will be
slow to move due to its orientation parallel to the upper flow. At
this time, it appears that the cold front will move through our
region with a band of heavy rain Tuesday night and/or Wednesday.
This forecast leans toward the slower ECMWF. The 00Z GFS does not
indicate much in the way of instability with the cold front in our
region, so for now will just have showers.

Heavy rainfall will be a concern, especially near the cold front
Tuesday night into Wednesday. Right now this band of heavy rainfall
is expected to move fast enough not to create significant flash
flooding in our region, but if the models trend stronger with the
eastern ridge, the heavy rainfall and flash flood potential could
increase over our region with later forecasts. Currently the
greatest threat for flash flooding is to our south and southwest.
Storm total QPF from Sunday night through Thursday ranges from
around 1" near I-64 to 2.5" in the Missouri Bootheel.

The gap periods Monday night and Tuesday will have our region mainly
in the warm sector, which could keep us mostly dry. However the
model consensus keeps quite a bit of convective activity across
southeast Missouri and southern Illinois, so we have likely or
better PoPs going in those areas with lesser chances farther
southeast. The QPF is rather light for such high PoPs in the warm
sector, so we may see a drying trend with future forecasts in this

For Wednesday night into Thursday, the models agree that mid/upper-
level impulses will stream northeast through the region and bring
more showers up across at least west Kentucky, however, they do not
agree on the timing. This will definitely keep the pressure on for
flooding potential at least over west Kentucky, but confidence is
not nearly as high as it was through Wednesday.

Temperatures will start out about 5 degrees below normal Sunday, but
they will climb above normal for the work week.


Issued at 1120 PM CDT Wed Mar 21 2018

Generally clear skies and light winds are expected through the
morning hours as high pressure moves over the Mississippi Valley. On
Thursday afternoon and evening, mid and high level clouds will
increase as warm advection develops on the back side of the high.
VFR will continue through Thursday evening.




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