148
FXUS63 KPAH 152348
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
648 PM CDT Mon Jul 15 2024

.KEY MESSAGES...

- A Heat Advisory remains in effect until Tuesday evening as
  peak heat index values between 105-110 degrees are expected.

- Unsettled weather returns on Tuesday as a cold front slowly
  moves towards the region. The greatest risk is from late
  Tuesday into Wednesday when multiple rounds of showers and
  thunderstorms are possible. A Flood Watch is now in effect
  Tuesday evening into Wednesday morning across portions of
  southern Illinois and southwest Indiana.

- High pressure will provide relief from the heat and humidity
  beginning Thursday through Sunday.

&&

.UPDATE...
Issued at 646 PM CDT Mon Jul 15 2024

Updated aviation discussion for 00Z TAFs.

&&

.DISCUSSION...
Issued at 328 PM CDT Mon Jul 15 2024

The heat and humidity remains the primary concern in the short term
as dewpoints once again are running above model guidance in the mid
70s to near 80 degrees. This translates to a heat index between 105
to 110 degrees this afternoon and again on Tuesday. A Heat Advisory
remains in effect until 01z Wednesday with maxTs progged in the low
to mid 90s. Overnight minTs will also be a bit warm tonight in the
mid 70s. Otherwise, scattered CU has once again developed this
afternoon as a 500 mb ridge of high pressure remains located over
the SW CONUS.

A period of unsettled weather begins to arrive on Tuesday as a
leading 500 mb shortwave downstream from a trough ejecting out
of Canada provides forcing for ascent. The latest CAMs show a MCS
developing south of the one that will move through the Chicago
area later this evening. The general idea is for a decaying MCS
to move towards the I-64 corridor early Tuesday morning, but
forecast confidence is low on the spatial coverage of any pcpn.
The parameters do not look terribly concerning should
thunderstorms occur. Have limit PoPs to a 30-35% with blends of
NBM and CONSShort given the uncertainty. One implication the
morning convection will likely have is where a residual outflow
boundary sets up, as this will be the main focus for the heavy
rainfall potential Tuesday night. It is worth noting any
convection during the day Tuesday could also provide some
relief from the heat up north. Have leaned closer to the NBM
25th percentile due to the possibility of more cloud cover.

As a cold front slowly sags southeast Tuesday evening, shower and
thunderstorm coverage becomes more likely from northwest to
southeast as a baroclinic zone sets up. The RAP13 shows 3000-4000
J/kg of MLCAPE and limited effective bulk shear around 25 kts 00z
Wednesday. Given a theta-e difference of 25 degrees and 0-3 km lapse
rates around 7.0 C/km, there remains a marginal risk in SPCs D2
outlook for a few isolated gusty severe storms capable of
producing downburst across northern portions of the CWA late
Tuesday afternoon into Tuesday evening. However, instability
quickly wanes with the loss of diurnal heating as a transition
to a heavy rain risk remains the main concern Tuesday night.

The 12z HREF PMM and latest 18z HRRR both show locally up to 2-4+
inches setting up right along the I-64 corridor across portions of
southern Illinois and southwest Indiana where training convection is
becoming probable. There are still some model differences in
the exact placement as the aformentioned outflow boundary will
play a big role, but overall confidence is increasing in the
potential for heavy rainfall to occur across portions of the FA.
PWATs remain progged around 2.00 inches with a light LCL-EL
cloud layer mean wind around 15 kts south of the boundary. This
favors the potential for multiple thunderstorms that will be
capable of producing torrential downpours. For this reason, have
gone ahead and issued a Flood Watch from 00z Tuesday evening
until 12z Wednesday morning. Across the rest of the FA, up to
1-2 inches of rainfall remains possible as additional rounds of
showers and thunderstorms push south Wednesday into Wednesday
night.

By Thursday morning, the cold front will eventually push south of
the FA, allowing for dry air to filter in across the FA from
the northeast as sfc high pressure builds into the lower Ohio
Valley. MaxTs are progged only in the low 80s by the NBM
Thursday and Friday with minTs ranging from the upper 50s to
lower 60s Thursday night. Dewpoints around 60 degrees will
certainly make this airmass quite refreshing! Temps do gradually
moderate over the weekend as a 500 mb trough digs across the
central Plains, but look to still remain slightly below normal.
As a disturbance approaches from the south, daily shower and
storm chances gradually increase by Sunday as the following week
looks to start off a bit more unsettled.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 646 PM CDT Mon Jul 15 2024

VFR conditions are anticipated through much of Tuesday. Remnants
of overnight convection to the north of the area will pose the
potential for scattered showers and thunderstorms across northern
reaches of the area late tonight into Tuesday morning, impacting
mainly KMVN and KEVV. Scattered thunderstorm development is also
possible late Tuesday afternoon into Tuesday evening across the
entire region. Southwest winds 5 to 8 knots will increase to 10
knots by late morning and afternoon on Tuesday. Some gusts to
15 knots are also expected.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory until 8 PM CDT Tuesday for ILZ075>078-080>094.
     Flood Watch from Tuesday evening through Wednesday morning for
     ILZ075>078-081>083.
MO...Heat Advisory until 8 PM CDT Tuesday for MOZ076-086-087-100-
     107>112-114.
IN...Heat Advisory until 8 PM CDT /9 PM EDT/ Tuesday for INZ081-082-
     085>088.
     Flood Watch from Tuesday evening through Wednesday morning for
     INZ081-082-085>088.
KY...Heat Advisory until 8 PM CDT Tuesday for KYZ001>022.

&&

$$

UPDATE...RJP
DISCUSSION...DW
AVIATION...RJP