434
FXUS63 KLMK 272317
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
717 PM EDT Mon May 27 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

*   Dry weather and below normal temperatures expected for most of
    the upcoming week.

*   Rain chances return for the weekend; severe weather is not
    expected at this time.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 315 PM EDT Mon May 27 2024

Synopsis...Stagnant upper-level trough over Great Lakes will keep
the Ohio Valley under broad cyclonic flow with several shortwave
energy pieces and mid-level wind speed maxima tracking north of the
Ohio River. At the surface, slow-moving cold front will continue
sagging southward tonight as high pressure ridge filters in from the
west.

Rest of Today...Surface observations and visible satellite imagery
locate the frontal boundary crossing the Ohio River early this
afternoon. A wind shift and dropping dewpoints is readily noted in
the postfrontal airmass with highs forecast to stay around 80
degrees in the modified warm sector and slightly lower north of the
boundary. In addition, the earlier stratus layer has evolved into a
cumulus deck and although convective temperatures have been met in
most cases and there is available instability along and ahead of the
front amid steepening low-level lapse rates, the lack of sufficient
mesoscale forcing, dry air aloft, and a capping inversion will
discourage any chances of precipitation this afternoon. Otherwise,
gusty winds will continue at least until sunset.

Tonight...Winds will subside after sunset as nighttime stability
decreases mixing in the BL. Decreasing dewpoints and lighter winds
will allow morning lows to be around seasonal spring values. Also,
the combination of light winds and recent rainfall could end up
favoring shallow fog across south-central KY later tonight which
could get more dense along the river valleys and other protected
areas. There is low to medium confidence in fog based on pattern and
HREF visibility output. Last but not least, upstream convection over
the MO and IL this afternoon will weaken as it moves towards
western Kentucky. Some models show isolated showers moving into the
area overnight, but chances are too low to include it in the
forecast at this moment.

Tomorrow...Quiet conditions will continue tomorrow as mid-level air
remains fairly dry and subsidence aloft maintains an inversion in
place. Winds will remain somewhat gusty from midmorning until sunset
once again with an average west to northwest direction. All HREF
members show afternoon convection over central Indiana as another
mid-level shortwave impulse moves over the region, but coverage
further south is uncertain at the moment and given other elements
favoring a dry forecast, decided to leave PoPs out.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 315 PM EDT Mon May 27 2024

Large-scale upper level troughing will continue across the eastern
half of North America for much of the mid-week period, with smaller-
scale shortwave disturbances swinging along its southern periphery.
One of these shortwave disturbances is expected to move across the
Midwest and upper portions of the Ohio Valley late Tuesday night
into Wednesday, providing support for mid-level ascent via
differential CVA. With model soundings showing reasonable amounts of
moisture in the 925-700 mb layer Wednesday, would expect there to be
an increase in diurnal cu, with a slight chance for a rain shower or
low-topped thunderstorm across portions of the KY Bluegrass
Wednesday afternoon.

Otherwise, much of the period Tuesday night through the end of the
week will be quiet across central Kentucky and southern Indiana,
with below normal temperatures expected. A reinforcing shot of cool
and dry air will move into the region Thursday into Friday behind
Wednesday`s shortwave disturbance as high pressure centered over
lower MI will promote low-level NE flow across the Ohio and TN
valleys. There is relatively high forecast confidence in dry weather
during this period, with EPS Ensemble mean PW values being below the
1st percentile for this time of year. Additionally, the ECMWF MinT
EFI is around -0.7 for Friday morning, indicating medium-high
confidence in anomalously cool low temperatures. The current
forecast calls for lows in the upper 40s and low 50s Friday morning,
but would not be surprised if some of our river valley locations
fall into the low-to-mid 40s. Daytime highs for the second half of
the week are generally expected in the mid-to-upper 70s.

This coming weekend, another upper trough will push into the north
central CONUS, with some of the associated energy diverting
southward into a low-amplitude wave that will move across the
Mississippi Valley on Saturday. As this wave moves into the Ohio
Valley, resultant low-level southerly flow and moisture return will
overspread the region next Saturday, leading to a return of daily
chances for showers and thunderstorms. With mid- and upper-level
flow expected to be weak, shear should be negligible, curtailing any
severe potential. CSU ML probabilities and CIPS severe analogs
reflects this, keeping any severe probabilities west of the
Mississippi Valley.

&&

.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 717 PM EDT Mon May 27 2024

Surface winds will remain elevated for the next few hours and then
begin to subside after sunset.  In general, VFR conditions are
expected throughout the upcoming TAF period.  Could see a little bit
of MVFR fog down at KBWG in the morning.  Winds will pick up on
Tuesday after sunrise with west to west-northwest winds of 10-14kts
and gusts of 20-24kts being possible through the afternoon and early
evening hours.  Winds will then slacken off again after sunset.

&&

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

&&

$$

SHORT TERM...ALL
LONG TERM....CSG
AVIATION.....MJ