Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 240814

Area Forecast Discussion
National Weather Service Paducah KY
314 AM CDT Sat Mar 24 2018

.SHORT TERM...(Today through Monday night)
Issued at 313 AM CDT Sat Mar 24 2018

Elevated warm advection showers will continue to gradually drift
from southwest to northeast this morning. A secondary mid-level
shortwave is currently rotating around a trough in eastern
Nebraska/western Iowa at this time, adding lift near a low west of
Kansas City this morning. This should help fill in new convective
activity across south central/southeast Missouri through
daybreak, working east across the rest of the WFO PAH forecast
area by late morning.

The 13km RAP seems to have a good handle on elevated instability
this morning, with most of the lightning activity developing with
a gradient of 100-200 J/KG in the 700-650 mb layer. Backed off
with the initial elevated thunder mention over southeast
Missouri/southwest Illinois until daybreak.

As the surface low rapidly develops southeastward near Perryville
by 4 pm this afternoon, surface-based warm sector showers and
thunderstorms will develop east of the weak cold front/weak dry
line. Dewpoints within the warm sector will range from 50 to 60
degrees Fahrenheit, providing amble fuel for convection as the
upper trough/mid-level slow slides southeast across the area
through midnight.

Temperatures will be in the upper 50s along and just south of the
warm front to lower 70s in the foothills of southeast Missouri
prior to the frontal passage. With more scattered convection
expected south of the warm front, rainfall amounts should remain
less than 0.5". Rainfall amounts will kick up north of a
Pinckneyville and Eddyville Illinois line onward to Princeton and
Elkton Kentucky. With elevated thunderstorms expected further to
the northeast, rainfall totals near 1.25" will not be out of the
question near a Petersburg and Dale Indiana.

High Pressure will briefly develop into the area late tonight and
through the daytime hours on Sunday, as another ridge builds in
at mid/upper levels through Sunday evening.

This ridge will move out early Monday morning, with ample warm
advection again moving moisture back northeast at lower levels
Monday morning, with another warm front working northeast through
afternoon and evening. Another round of showers will develop along
a warm front will mostly impact southwest Indiana and the
Pennyrile region of West Kentucky.

By Monday night, as the upper level flow begins to become
southwest flow the bulk of the moisture advection and lift will
switch westward into southwest/south central Missouri and West
Central Illinois.

The Canadian guidance seemed to initialize well and was in line
with the ECWMF and NAM-WRF guidance in the short term. Forecast
confidence is fair to good (up to 65%) today through Monday night.

.LONG TERM...(Tuesday through Friday)
Issued at 313 AM CDT Sat Mar 24 2018

Forecast confidence is well above normal through Wednesday and then
decreases heading into the end of the week and next weekend.

Tuesday will begin with an upper-level ridge extending from the Gulf
northeast up the Appalachians and a complex trough extending from
the northern Plains to the Four Corners. At the surface a cold front
will extend from Oklahoma northeast into Wisconsin. Our region will
be under southwest flow aloft, with strong and gusty south winds
advecting Gulf moisture northward toward the boundary. Convection
will be ongoing along or just southeast of the cold front, generally
just to the northwest of our area.

As the northern portion of the upper trough pushes eastward into the
Great Lakes through Wednesday, the front and primary band of
precipitation will push southeast into and most likely through our
area. The ECMWF continues to be stronger with the upper ridge in the
east, and is a bit slower with the frontal passage. It leaves open
the possibility of the boundary stalling out over or just southeast
of west Kentucky, but even it has trended faster and ultimately
drier for our region. The bottom line is that Tuesday and Tuesday
night look wet, but much of the area should be dry Wednesday and
Wednesday night.

With the faster progression of the boundary through the region,
precipitation totals have trended down significantly from
yesterday`s levels. Totals from Sunday night through Thursday night
now range from 1.25" over southwest Indiana to 2.5"-3" along the far
western and southern border regions. This is still quite a bit of
rain, but over a 4-5 day period it should not cause to much trouble,
especially with the mainstem rivers starting out well below flood
stage. Instability is still hard to find, but some elevated
instability does exist mainly over southeast Missouri and southern
Illinois as the main band of rain begins to move into the area

The 00Z models diverge a bit Thursday with the upper trough, in some
form, moving east through the Quad State. The ECMWF develops a wave
along the surface boundary, which is just to our southeast, and
brings a quarter to a half inch of rain over the entire area
Thursday. The GFS has the boundary farther southeast, and has
scattered showers moving east across the region Thursday night, with
only some light precipitation in the southeast during the day. The
GEM/CMC has a much weaker trough and keeps our area dry Thursday and
Thursday night. We will leave chance PoPs over the entire area both
periods to acknowledge the possibility, but not fully endorse the
wetter ECMWF just yet.

All indications are that the area will clear quickly behind the
upper trough passage, and there should be plenty of sunshine next
Friday. However, surface high pressure will hold temperatures down
about 5 degrees below normal with highs only in the middle 50s.

The flow aloft will really relax and become nearly zonal early next
weekend. At the surface a warm front will be moving through the
region Saturday into Saturday night. The ECWMF and GFS agree on
these basics, but differ in the specific timing and
coverage/intensity of the precipitation. For now we will lean toward
the GFS and have just small chances of showers over the northern
half of the forecast area, mainly Saturday morning. The GEM/CMC is
much wetter and is a definite outlier at this point, so it was
ignored for this forecast.

Looking another day out for Easter Sunday, it looks like the entire
area should be in the warm sector with stout south winds and
generally mild conditions. A few showers cannot be ruled out, but we
should be mostly dry.


Issued at 1145 PM CDT Fri Mar 23 2018

Showers will continue across the area overnight, with some
isolated TSRA possible after 06z. Cigs should generally lower to
MVFR with occasional IFR cigs from 06z on. Visibility restrictions
will come with heavier bursts of rain, generally MVFR to possibly
IFR. East winds will gradually become southeast then southwest
across southeast MO into west KY, with mainly easterly winds north
of a surface low track across our area tomorrow, including
southern IL and southwest IN. Speed generally 8 to 15 kts, with
some gusts 20 to 25+ kts. Thunder chances will be most likely at
KCGI/KPAH during the day on Saturday. Rain chances will end at
least at KCGI and KPAH, but a few showers will likely continue
through the end of the period at the other sites.




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