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000
FXUS63 KLMK 211854
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
254 PM EDT Sun Apr 21 2024

.KEY MESSAGES...

*   Frost Advisory in effect tonight through Monday morning.

*   Showers and an isolated thunderstorm or two Tuesday night. No
    severe weather.

*   Shower and thunderstorm chances Friday-Saturday.

*   No significant frost threats after tonight. Coolest night in the
    extended forecast will be Wednesday night with lows in the upper
    30s in southern Indiana and north central Kentucky.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 253 PM EDT Sun Apr 21 2024

Currently on visible satellite imagery you can see scattered Cu
field across Indiana into northern KY. These clouds were ahead of
the mid-level shortwave axis dropping southward through IN into KY.

The shortwave trough axis will continue work through Kentucky
overnight with a core of cold 850mb temperatures of 0 to -3 located
over the state through the overnight. Sfc high pressure over the
Central Plains will continue to build eastward helping to clear
skies and provide light to calm winds over the area. The combination
of cold air aloft, clear skies and light winds will allow for frost
to develop overnight. The Frost Advisory remains in effect for
tonight into Monday morning for all of our CWA. Lows will be in the
mid 30s with a few locations into the low 30s.

High pressure will settle in over the Lower Mississippi Valley and
spread across the Ohio Valley as upper ridging builds in from the
west. Winds will remain light with clear skies providing plenty of
sunshine. Highs will warm to just a few degrees below normal into
the low/mid 60s.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 253 PM EDT Sun Apr 21 2024

Monday Night through Wednesday Night...

High pressure at the surface and ridging aloft will provide dry
weather for the region Monday night.  With the high pressure ridge
at the surface to our east, we`ll be in a southern flow Monday night
which will keep low temperatures in the lower to middle 40s. Tuesday
will feature increasing cloud cover as a shortwave trough axis moves
through the Great Lakes.  Moisture return across the region will be
rather short and the quality of moisture looks not all that great.
As the trough axis shifts through the Great Lakes, a cold front will
push through the area and convergence along that boundary will bring
a round of showers to the region.  A few thunderstorms could occur
with this front, but the instability and shear are very very
marginal here.  Rainfall amounts of up to a quarter of an inch will
be possible.  Highs Tuesday will be in the upper 60s to the lower
70s with lows Tuesday night falling into the mid-upper 40s across
southern Indiana and lower 50s across Kentucky.

Upper trough axis will work eastward on Wednesday with partial
clearing taking place. Highs will be in the upper 60s to around 70
in most locations.  Wednesday night might bring another low chance
of frost to the region, depending on sky cover and near surface
winds.  We`ll still have a bit of a pressure gradient across the
region, so winds may not allow good radiational cooling.  If frost
were to develop, our southeast Indiana counties and the northern
Bluegrass region would be at most risk where lows will dip into the
upper 30s.  Elsewhere, lower 40s are expected.

Thursday through Sunday...

Dry weather looks to continue into Thursday as we`ll remain in a
northwest flow pattern as ridging will be located west of us.  Highs
should warm into the upper 60s to around 70 across southern Indiana
and the northern half of Kentucky.  Lower 70s are likely across
southern KY.  As ridging builds eastward, a warm frontal boundary
will lift across the region Thursday night and into Friday which may
bring a band of light rain showers as it passes through.  The ridge
will be shunted off to the east fairly quickly and we`ll get back
into a southwesterly pattern aloft with a large trough axis anchored
over the western CONUS.  From Friday through the weekend, we`ll have
to be on guard for occasional perturbations that will be rotating
through the trough base and then heading from the Plains into the
Midwest.  These perturbations will likely result in episodic bouts
of severe convection from the Plains into the Midwest and some of
these bouts of convection could produce outflows that generate some
scattered convection across our region.  Overall, the Friday-Sunday
period looks to be mostly dry but we`ll keep diurnally driven
convective PoP chances in the forecast.  Model soundings do show
diurnally driven instability being present, but shear profiles look
rather marginal on Friday/Saturday and a bit more weaker on Sunday.
CSU machine learning as well as the bulk of the ensemble data agree
with this line of thinking and keeps the main threats of severe
convection well to our west through the period.  Temperatures will
return to above normal levels with highs in the 75-80 degree range
for Friday and Saturday.  Low-mid 80s look likely for Sunday with
overnight lows in the 50s/60s.

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 120 PM EDT Sun Apr 21 2024

Few scattered mid-level Cu along with gusty northwest winds will be
around through the afternoon to just after sunset this evening.
Winds will diminish and clouds will clear as sfc high over the
Central Plains works eastward overnight. It will remain VFR with
mainly clear skies and light winds for most of the rest of the
forecast period.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Frost Advisory from 1 AM EDT /midnight CDT/ to 9 AM EDT /8 AM
     CDT/ Monday for KYZ023>043-045>049-053>057-061>067-
     070>078-081-082.
IN...Frost Advisory from 1 AM EDT /midnight CDT/ to 9 AM EDT /8 AM
     CDT/ Monday for INZ076>079-083-084-089>092.

&&

$$

SHORT TERM...BTN
LONG TERM...MJ
AVIATION...BTN