Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 191622
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1222 PM EDT Thu Apr 19 2018

.Forecast Update...
Issued at 1205 PM EDT Thu Apr 19 2018

Temps are struggling under cold air advection and trapped strato-cu,
but the cloud deck is thinning quite nicely. No updates to the
forecast for this afternoon as we should just be able to squeeze out
the advertised max temps, though it may take until just before
sunset to get enough clearing.

Will be looking closely at wind fields for tonight as that could
throw a monkey wrench into our frost/freeze potential. If the winds
stay up, that would limit us to a marginal freeze, perhaps only in
the eastern valleys. And frost would be largely off the table. No
changes yet.

&&

.Short Term...(Today through Friday)
Issued at 304 AM EDT Thu Apr 19 2018

...Freeze Warning & Frost Advisory Later Tonight...

Post frontal winds are still gusting in the 25 to 35 mph range at
this hour, however have dropped well below Wind Advisory criteria.
Let that headline expire at 2 AM EDT. Temperatures will steadily
drop to the upper 30s by sunrise.

Expect plenty of cloud this morning, before clouds try to clear out
from N to S later in the afternoon. The early cloud cover combined
with steady NW and NNW winds will keep temperatures down today. Look
for highs only in the low to mid 50s, nearly a full 15 degrees below
normal for this time of year.

The big concern for tonight will be the potential for widespread
frost across the southern 2/3 of our CWA, and potential for a hard
freeze across the northern 1/3 of the CWA. This isn`t a slam dunk
given a couple of limiting factors. Surface high pressure is
expected to settle near the Quad Cities by dawn on Friday, quite
displaced from our CWA. As a result, surface winds could stay up
around 3 to 7 mph overnight. This could limit frost production and
keep the lower atmosphere mixed enough to not drop into the hard
freeze range. Despite that, conditions look close enough to go ahead
with the headlines along with surrounding offices. Decoupled valleys
and the typical cool spots will be most likely to see the hard
freeze.

High pressure at the surface and dry NW flow aloft will continue to
dominate on Friday. Temps will be a little milder than today, but
will still be below normal after a cool start. Look for lower 60s in
most spots.

.Long Term...(Friday night through Wednesday)
Issued at 304 AM EDT Thu Apr 19 2018

Friday Night - Sunday...

Progressive upper ridging and high pressure at the surface will
control the weather pattern this weekend. This will bring dry
conditions and high temperatures slightly (~5 degrees) below normal
for this time of year. After chilly overnight lows in the mid and
upper 30s on Friday night, we`ll see milder lows in the low and mid
40s for Saturday night. Temps should be around 60 degrees for
outdoor activities on the Louisville water front Saturday night. Did
want to mention that frost will again be a possibility on Friday
night/Saturday morning over much of the area.

Sunday Night - Tuesday...

A closed upper low looks to slide across the Tennessee Valley to
start the new work week. As this occurs, the northern edge of the
precipitation shield associated with mid level deformation looks to
slide across our area. Central and southern Kentucky will have the
highest chances for rain, with question whether the precipitation
will extend far enough north to reach the southern Indiana counties.
The best chance for precip amounts up to a half an inch will be
along the KY/TN border.

Overnight lows should range between 45 and 50 degrees each night,
with afternoon highs just below normal in the mid to upper 60s.

Tuesday Night - Wednesday...

Looking for a brief lull in precipitation activity on Tuesday night
as the closed upper low/weak open wave moves off to the east and the
next disturbance slides into the Great Lakes region. Will likely
carry small chance pops on Tuesday night to account for timing
difference, but the better chance for more rain looks to be by
Wednesday. The trend of lows around 50 and highs just below normal
in the mid to upper 60s should continue.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1220 PM EDT Thu Apr 19 2018

Dry weather is expected through this TAF period as high pressure
builds in from the north. Ceilings are expected to improve to VFR at
all sites over the next few hours. Clouds should then scatter out
late this afternoon into this evening with clear skies expected
overnight into tomorrow morning. Wind gusts will decrease late this
afternoon. Winds overnight will be 4-6 knots out of the north to
northwest, shifting to easterly tomorrow morning.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Freeze Warning from 1 AM to 10 AM EDT Friday for INZ076>079-083-
     092.

     Frost Advisory from 1 AM EDT /midnight CDT/ to 10 AM EDT /9 AM
     CDT/ Friday for INZ084-089>091.

KY...Freeze Warning from 1 AM to 10 AM EDT Friday for KYZ031>037-
     039>043-047>049-056-057.

     Frost Advisory from 1 AM EDT /midnight CDT/ to 10 AM EDT /9 AM
     CDT/ Friday for KYZ023>030-038-045-046-053>055-061>067-
     070>078-081-082.

&&

$$

Update...RAS
Short Term...BJS
Long Term...BJS
Aviation...EER



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