158
FXUS63 KPAH 161521
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1021 AM CDT Tue Jul 16 2024

.KEY MESSAGES...

- Hot and humid conditions will be most likely over southeast
  Missouri and west Kentucky, especially near the southern
  borders. Adjustments to the Heat Advisory are likely by
  midday.

- Scattered to numerous thunderstorms have already moved into
  northern portions of the region and some heavy rainfall and
  flooding have already occurred. The timing of the Flood Watch
  was changed to begin this morning. The Flood Watch area has
  not changed and it is still in effect until 7 AM Wednesday.

- An isolated severe thunderstorm is possible this afternoon and
  this evening, mainly over southeast Missouri, the southern tip
  of Illinois and west Kentucky. Damaging wind gusts will be
  the primary threat.

- Dry, cooler, and much less humid weather will arrive Thursday
  and continue into the weekend. A small chance of thunderstorms
  returns to the forecast late in the weekend into early next
  week for parts of western Kentucky.

&&

.UPDATE...
Issued at 1021 AM CDT Tue Jul 16 2024

The MCS that moved into the I-64 corridor this morning has
wrecked the forecast for today. First the Flood Watch valid time
was changed to begin this morning as flooding has already
developed over Jefferson county. The end time is still 7 AM
Wednesday.

The HRRR suggests that we will see a line of convection develop
over southeast Missouri this afternoon and move southeast
through west Kentucky. Damaging winds will be possible, but
torrential rainfall and flooding will also be possible. Another
round of convection is expected late tonight into Wednesday.
This will have mainly a heavy rainfall and flooding concern.

And then there is the Heat Advisory. Will likely cancel a good
portion of it around midday, with cloud cover and convection
holding down temperatures. Southeast Missouri and southern
portions of west Kentucky are the most likely areas to reach
105F.

&&

.DISCUSSION...
Issued at 335 AM CDT Tue Jul 16 2024

Today through Wednesday night...The region is coming under the
influence of an increasingly zonal H5 flow, with a surface
frontal boundary extending from eastern IA into central MO
approaching the area from the northwest. Debris clouds from a
decaying MCS across central IL/IN are moving south into the
region. Depending on how the decaying MCS evolves, some
precipitation may impact far northern and northeastern parts of
the forecast area north of I-64 this morning.

There is growing uncertainty regarding whether the northern
parts of the forecast area will reach Heat Advisory criteria
due to lingering clouds and precipitation chances. However,
after collaborating with neighboring offices, decided to keep
the ongoing Heat Advisory in place for now, but its northern
portions may need to be trimmed later today.

The main wave of shower and thunderstorms activity looks to
arrive late this afternoon through tonight as the cold front
approaches from the northwest along with a shortwave trough.
This will lead to fairly widespread convective development
across central and eastern MO, which will grow upscale into a
MCS and move through the forecast area. While bulk shear will be
quite limited, high temperatures in the lower to middle 90s and
extremely gooey dew points in the upper 70s to lower 80s should
allow for robust instability to develop by this afternoon. SPC`s
Day 1 Convective Outlook includes a marginal risk of severe
thunderstorms across the entire forecast area, and that looks
reasonable. The primary severe risk will be isolated damaging
winds from downbursts and any linear segments that can organize.

With the frontal boundary sagging into the region tonight into
Wednesday morning, training thunderstorms and heavy rain will
become the main concern. Based on the latest WPC QPF and HREF
QPF probabilities, opted to expand the inherited Flood Watch to
include parts of northwest KY, more of southern IL, and the
Ozark Foothills of southeast MO (in addition to the existing
Flood Watch in southeast IL and southwest IN). In the Flood
Watch area, most areas stand to get a broad brush of 1.5-3.0" of
rain, with locally higher amounts possible. This would be
enough rain to cause flash flooding issues if realized.
Locations further south and outside of the Flood Watch stand to
receive a healthy rain as well, mainly 0.5-1.5". Did not adjust
the timing of the Flood Watch from the initial 00-12z Wednesday
timing, but some locally heavy rain may linger into the 12-18z
Wednesday period in southwest IN and northwest KY.

Rainfall rates will trend down during the day on Wednesday as
the better forcing moves east of the region. However, scattered
to widespread showers and thunderstorms will linger through much
of the day. This will keep high temperatures limited to the
lower to middle 80s. The greatest coverage in precipitation will
gradually shift from north to south as the cold front clears the
region.

Thursday through Saturday...Canadian high pressure will dry us
out for the latter half of the work into the weekend. Cannot
rule out a few AM showers along the KY/TN border Thursday
morning, but the great majority of the region will be dry by
this point. High temperatures will be delightfully cool for the
middle of July, in the upper 70s to lower 80s! Low temperatures
Thursday night will be just as refreshing, falling into the
upper 50s to lower 60s. Temperatures will moderate slightly
Friday and Saturday, climbing into the lower to middle 80s.
However, humidity levels will remain very comfortable. Overnight
lows Friday and Saturday night will stay mainly in the lower
60s.

Sunday and Monday...Model guidance has trended a bit more
unsettled for this period, especially for parts of west KY. The
culprit for this will be a plume of tropical moisture that will
be pulled northward from the Gulf of Mexico. The moisture will
be hard- pressed to advance much further north than the
Tennessee River Valley due to high pressure positioned to the
north. However, isolated to widely scattered thunderstorms look
to return to the forecast in the southern KY Pennyrile region
Sunday and Monday. High temperatures will still be slightly
cooler than normal, reaching the lower to middle 80s.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 632 AM CDT Tue Jul 16 2024

For the 12z TAF package, a decaying cluster of thunderstorms
will impact MVN, EVV, and OWB through 13-15z before dry weather
returns through late afternoon. Another round of storms will
develop west of the region near STL and push through the region
tonight. Cigs and vsbys will be VFR during dry periods, but
MVFR or lower restrictions are likely during thunderstorm
activity. Winds outside of thunderstorms will be SW at 8-12 kts
with gusts to 15-20 kts this afternoon. Tonight winds will relax
and become light and variable.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory until 8 PM CDT this evening for ILZ075>078-
     080>094.
     Flood Watch through Wednesday morning for ILZ075>078-080>089.
MO...Heat Advisory until 8 PM CDT this evening for MOZ076-086-087-
     100-107>112-114.
     Flood Watch through Wednesday morning for MOZ076-086-087-100-
     107-108.
IN...Heat Advisory until 8 PM CDT /9 PM EDT/ this evening for
     INZ081-082-085>088.
     Flood Watch through Wednesday morning for INZ081-082-085>088.
KY...Heat Advisory until 8 PM CDT this evening for KYZ001>022.
     Flood Watch through Wednesday morning for KYZ014-018-019.

&&

$$

UPDATE...DRS
DISCUSSION...DWS
AVIATION...DWS