River Flood Warning 66, NWS Paducah, KY

Area Forecast Discussion
National Weather Service Paducah KY
224 PM CDT Mon May 4 2020

.SHORT TERM...(Tonight through Tuesday night)
Issued at 224 PM CDT Mon May 4 2020

The main concern in the near term remains the potential for
showers and thunderstorms late this afternoon and tonight,
including the threat for severe thunderstorms late this afternoon
into the evening hours.

Low pressure will track from the southern Plains across southern
Missouri tonight and into western Kentucky by Tuesday morning.
The low will generally track along a frontal boundary stalled to
the south of the area across Arkansas into Tennessee. Dynamics
with the system are supportive of organized thunderstorms late
this afternoon and into the evening hours. However, the main
limiting factor is surface-based instability, which is currently
held at bay south of the stalled frontal boundary. Even 0-1 km
MLCAPE struggles to reach much higher than 1000 J/kg across most
of the area by 00Z, with the exception of far southeast Missouri
and the southwest tip of western Kentucky near the Arkansas and
Tennessee state lines. And looking at the SPC mesoanalysis page,
DCAPE values of 200-500 J/kg are generally confined to southeast
Missouri as well.

As a result, the convective complexes currently over Missouri
should continue to move southeastward along the instability
gradient through the late afternoon and evening hours. The
greatest threat for damaging wind will be across southeast
Missouri into far western Kentucky, where instability will be
greatest. Elsewhere, the main concern appears to be from large
hail with steep mid level lapse rates greater than 8 C/km. Most of
the severe threat should be over by mid evening, though the
potential for thunder will linger well into the night.

Any lingering shower activity should taper off from west to east
late tonight and Tuesday morning as the low pressure center moves
off to the east. Clearing will likely be very slow to occur on
Tuesday, so much of the area may not warm as much as would
otherwise be expected. After lows in the upper 50s to lower 60s
tonight, highs on Tuesday are forecast to range from near 60 north
to around 70 south. Lows should range from 40 to 45 across much of
the area Tuesday night.

.LONG TERM...(Wednesday through Monday)
Issued at 224 PM CDT Mon May 4 2020

In the long term forecast period, strong blocking over the Gulf of
Alaska will displace an upper-level trough of Arctic origins. This
trough will become nearly stationary over Hudson Bay, placing the
PAH FA under broad cyclonic flow in addition to bringing well-below
normal temperatures. Disturbances embedded within this cyclonic flow
will rotate southeast around the base of the trough and provide
opportunities for light rain Wednesday and perhaps a more
widespread, soaking rain Thursday into Friday.

A weak, moisture-starved shortwave trough will pivot through the
forecast area from the Upper Midwest Wednesday. The main impact will
be an increase in cloud cover, but isolated light rain showers are
possible as well. A better chance of precipitation arrives Thursday
into Friday, as the shortwave ejecting from the Upper Midwest phases
with a subtropical jet impulse. Surface low pressure will develop
over the southern Plains and traverse roughly parallel to the Ohio
River. With a better moisture source and more impressive dynamics,
rainfall looks to be more widespread in coverage, with QPF amounts
of 0.25 to 0.50 of an inch. At this time, CAPE of any variety looks
to be minuscule, so am not currently expecting thunder.

Surface high pressure settles over the region for the weekend,
setting up the potential for near record lows and a non-zero risk of
rare late season patchy frost Saturday morning and perhaps again
Sunday morning. At this time, the NBM initialization yields morning
lows of 36-40 degrees and 38-42 degrees on Saturday and Sunday
mornings, respectively. Depending on wind and cloud cover, the
potential for frost could rise or fall at this range. High
temperatures Wednesday will range from the upper 50s in the EVV Tri-
State to upper 60s in the MO Bootheel. After a brief warmup into the
60s Thursday, highs the remainder of the forecast period will range
from the upper 50s to middle 60s, respectively from north to south.
These values will be about 10-15 degrees below normal.

&&

.AVIATION...
Issued at 1249 PM CDT Mon May 4 2020

While VFR conditions will start the afternoon, a transition to
MVFR ceilings is anticipated by late afternoon and especially this
evening as low pressure approaches from the Plains. Periods of
showers and scattered thunderstorms will spread across the region
from the west late this afternoon and into the evening hours.
Thunder should become much more sparse by late evening and
overnight as scattered showers persist, accompanied by low end
MVFR and IFR ceilings in some cases. Ceilings should gradually
improve back to MVFR through Tuesday morning as lingering showers
taper off. East winds around 10 knots today will become northwest
10 to 15 knots on Tuesday.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

SHORT TERM...RJP
LONG TERM...DWS
AVIATION...RJP

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