-- Discussion containing changed information from previous version are highlighted. --
674
FXUS63 KLMK 011033
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
633 AM EDT Mon Jul 1 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Very pleasant weather to start July with temperatures around 10
    degrees below normal for both today and tonight.

*   Unsettled weather Wednesday through Friday and possibly into the
    weekend with daily chances of showers and storms. Rain chances
    on Independence Day 70-90%. Widespread severe weather not
    expected, but locally torrential downpours and gusty winds will
    be possible. Lightning is a threat with any thunderstorm.

*   Heat index Wednesday afternoon may reach 100-105 degrees.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 259 AM EDT Mon Jul 1 2024

July kicks off with very pleasant weather and plenty of sunshine for
the Ohio Valley, thanks to sfc high pressure centered to our north.
Winds from the NNE will continue to promote a CAA pattern and filter
in much drier air. Dewpoints this afternoon will drop into the upper
40s and lower 50s, which will be quite a noticeable change from the
last few days. Temperatures will peak in the upper 70s and low 80s
this afternoon, some 10 degrees below climate normals.

For tonight, the sfc high will be slowly shifting eastward. A very
weak and subtle mid-level wave will be riding over the ridge, and
should bring an increase in mid-level clouds this evening.
Otherwise, light sfc winds will become an easterly flow by early
Tuesday morning as the high moves away. It should be a good
radiational cooling night, and will likely see temps cool into the
50s. Lows will be around 10 degrees cooler than normal.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 259 AM EDT Mon Jul 1 2024

Southern U.S. upper ridging will build northward into the Ohio
Valley Tuesday, while surface high pressure crosses New York. This
will put us in a warm return flow regime, resulting in a return to
summertime heat with highs around 90. Moisture from a slightly
anomalously warm Gulf of Mexico will flow northward, causing a 12-14
degree rise in dew points over the course of the day.

Wednesday will start off warm with sunrise temperatures in the lower
and middle 70s. The New York high will slip off the East Coast and
the upper ridge will flatten slightly south of an upper trough over
eastern Canada. We`ll have weak shear and very weak mid-level lapse
rates, but plenty of moisture and instability for some diurnal
thunderstorm development, especially in southern Indiana and west
central Kentucky farther away from the southern upper ridge. Locally
torrential downpours and gusty winds would be the main threats. Slow
storm motion around 10-20 mph may lead to local water issues in the
heavier storms, though the storms should rain themselves out fairly
quickly. With the heat and humidity, heat index values will reach
the 100-105 degree range (WBGT 83-86, moderate). Wednesday should be
the most uncomfortable day of the week.

The Fourth: Strengthening 5H shortwave trough over the northern
Plains will further suppress the southern upper ridge while a warm
and muggy air mass remains in place. Widespread showers and storms
are expected. The best chance for severe storms will be to our
northwest over Nebraska, northern Missouri, and Iowa closer to a
500mb speed max cruising across the central Plains. However, once
again locally torrential downpours and gusty winds will be possible
with the storms here in the Ohio Valley with seasonally strong
instability, weak shear, high atmospheric moisture content, and very
high freezing levels. And, not to be forgotten, lightning is a
threat with any thunderstorm. Folks with plans for outdoor
Independence Day activities should monitor the forecast closely.

Like Wednesday, Thursday will also start off quite warm with
temperatures in the 70s. ECMWF EFI shows unusually warm minimum
temperatures expected, and the current forecast puts record warm
lows for the 4th in jeopardy.

Thursday`s upper wave will cross the Great Lakes and continue our
thunderstorm chances here, with additional locally heavy rains
possible. Confidence in the forecast decreases for the weekend, but
the region will still be on the periphery of the southern upper
ridge with occasional impulses in the faster flow across the
northern half of the country, so will hold on to small PoPs.

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
-- Changed Discussion --
Issued at 633 AM EDT Mon Jul 1 2024

VFR conditions are expected through the current forecast period as
sfc high pressure sits to our north. Winds will be from the NE
today, generally sustained around 10-12kts, though some breezes
upwards of 20kts are possible this afternoon. SKC is expected until
this evening, when we should see some high-level cirrus begin to
quietly stream across the region. No impacts to the terminals
expected with this TAF package.
-- End Changed Discussion --

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...CJP
LONG TERM...13
AVIATION...CJP