Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 212319
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
619 PM EST Sun Jan 21 2018

...Updated Aviation Discussion...

.Short Term...(This evening through Monday night)
Issued at 309 PM EST Sun Jan 21 2018

Now - Tonight...

Temps are ranging in the mid and upper 50s to low 60s at this hour.
A few light showers and patches of drizzle are noted on radar as
weak isentropic ascent continues over the region. The main focus for
shower activity for the rest of the afternoon and evening will be
1.) over portions of southern and eastern CWA, and 2.) along and
north of I-64. Otherwise, expect a mild and mostly dry evening and
overnight as the warm sector becomes firmly established over the
area.

Steady southerly flow will gradually increase tonight as the low
level jet spreads in. As a result of the cloudy skies and mixy warm
advection, temps will stay quite mild overnight. Only have lows
dropping to around 50.

Monday - Monday Night...

A mature cyclone will move from the upper Midwest to the Great Lakes
during this time, with a trailing cold front passing through our
area Monday evening. Ahead of this front, expect widespread rainfall
to break out just after daybreak across our western CWA, steadily
progressing eastward through the day. Given good moisture transport
on a 50+ knot low level jet, combined with the exit region dynamics
of an upper jet a broken to solid line of rain showers is expected
to steadily move through on Monday. Going with 80-100% Pops
depending on location with most places seeing between a quarter and
a third of an inch of rainfall. Have kept the idea of an isolated
chance at a rumble of thunder Monday afternoon and evening, but
don`t expect more than a few random strikes. Nevertheless, given the
strong forcing and a few hints of some elevated instability can`t
rule it out.

Highs Monday should top out in the upper 50s and low 60s, with gusty
S winds through the day. A mid level dry slot will work into the
area from W to E later Monday afternoon into Monday evening,
shutting most of the precip off as it does so. Will likely see the
gustiest winds during this time with peak gusts still expected to
range up to 35 mph well into the night. Temps drop off behind the
front with the possibility of some lingering drizzle Tuesday night
as low level moisture remains trapped. Lows drop to the upper 30s,
which should be just mild enough to keep p-type in rain form.

.Long Term...(Tuesday through Sunday)
Issued at 309 PM EST Sun Jan 21 2018

Tuesday...

Trapped low level moisture associated with a mature system over the
eastern Great Lakes will allow for some lingering light rain showers
on Tuesday. Temps should mostly be in the upper 30s that morning,
and just warm enough to keep p-type all rain. Southern Indiana and
northern KY will have the best shot at measurable rainfall.
Otherwise, most areas should stay dry with highs only in the lower
40s.

Tuesday Night - Friday Night...

Dry NW flow aloft and surface high pressure then dominate the
pattern to the end of the work week before progressive upper ridging
quickly slides through Friday. This will lead to dry conditions with
temps steadily trending milder. For example, highs Wednesday in the
low 40s will give way to highs in the mid and upper 50s by Friday.
Lows in the mid and upper 20s Tuesday and Wednesday nights, will
give way to lows in the low 40s by Friday night. The milder Friday
night will mainly be due to the steady southerly flow that takes
over combined with increased cloud cover.

Saturday - Sunday...

The upper pattern will be highly amplified by the weekend as a
central CONUS trough is bookended by ridging on each coast. The Ohio
Valley will be in the deep SW flow ahead of the trough axis, leading
to deep moisture transport along with increasing large scale lift as
the trough approaches. In addition, a cold front will trail from an
eastern Canada surface low, with secondary cyclogenesis possibly
occurring somewhere from the Gulf Coast states up the Appalachian
spine in response to upper level divergence associated with
strengthening jetting. The end result will be widespread rainfall
Saturday into Sunday. We`ll have to watch and see if enough
lingering moisture is possible for a change over to some snow on the
back side. Much will depend on timing and strength of secondary
surface cyclogenesis for this to occur, so won`t get too entrenched
in details at this point. Saturday highs in the 50s, will give way
to falling temps on Sunday as the front passes, assuming models are
correct with timing.

&&

.Aviation...(00Z TAF Issuance)
Issued at 619 PM EST Sun Jan 21 2018

Low ceilings remain across the northern portions of the forecast
area.  These are expected to lift into the VFR range as the evening
wears on.  A few light showers are moving northeast, just west of
SDF.  Will carry a few hours of VCSH to cover this as it passes by.
Low-level winds will pick up tonight, so LLWS wording will continue
in this TAF package at KBWG/KHNB/KSDF.

For tomorrow, Plains low will advance into the Midwest and push a
cold front towards the region. Rain showers look to increase from
west to east tomorrow morning and become more widespread by
afternoon.  Winds will remain quite gusty out of the southwest
throughout the day.

&&

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

$$

Short Term...BJS
Long Term....BJS
Aviation.....MJ



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