Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 240649

Area Forecast Discussion
National Weather Service Louisville KY
249 AM EDT Tue Oct 24 2017

.Short Term...(Today through Wednesday)
Issued at 232 AM EDT Tue Oct 24 2017

Latest surface analysis showed a 989 mb low over northern Michigan
while a weak front was passing through western KY and southwest IN.
Aloft, large scale trough encompasses much of the Great Lakes and
lower Ohio Valley. Regional radar shows an area of showers pivoting
through the area. Finally, readings generally were in the upper 40s
to lower 50s.

For today, plan on the current showers to push east of the area by
mid morning, likely to be along/east of I-75 corridor by sunrise. In
its wake, expect blustery westerly winds increasing into the
afternoon hours. Soundings show wind gusts 20 to 30 mph at times.
Skies should vary from mostly cloudy to overcast as steep low-level
lapse rates favor plenty of strato-cu.

Toward the mid to late afternoon hours, another lobe of energy
associated with the upper level low will pivot through. While QPF
generated by the models is light, soundings show deep enough
saturation to warrant chance of rain showers or perhaps drizzle
across southern Indiana and north central Kentucky. The hi-res
models such as the WRF-ARW, NSSL WRF, and latest runs of the HRRR
show this idea fairly well. Trended precipitation chances a bit
higher in the 3p-9p time frame.

Temperatures today won`t see a large diurnal jump with plenty of
clouds and continued cold air advection. Look for readings to top
out in the lower 50s across southern Indiana, to mid/upper 50s
across central Kentucky. Lows tonight will drop into the lower 40s
with some of the cooler spots possibly reaching the upper 30s if
clouds clear and winds relax.

On Wednesday, a northwest flow system will drop through the Upper
Midwest and lower Ohio Valley. The 24.00z guidance has trended
further southwest and a little wetter compared to previous cycles,
generating a light QPF swath from central IN into parts of
central/eastern KY. The latest timing would bring chances for rain
showers into the area during the afternoon and evening hours. This
could be a cold rain with some guidance pointing to highs staying in
the 40s, especially across southern IN and north central KY.


.Long Term...(Wednesday night through Monday)
Issued at 235 AM EDT Tue Oct 24 2017

For Thursday into Friday, brief ridging aloft, and southwesterly
flow ahead of the next weather system will bring our warmest and
most seasonable weather of the entire forecast period. Look for
breezy afternoons helping to bring highs into the 60s, perhaps near
70 on Friday with stronger warm air advection.

24.00z guidance has come into slightly better agreement with the
phasing and timing of the next weather system. As an upper trough
dives into the central Plains, a cold front will slowly begin to
work east into the area. The bulk of the rain looks to hold off
until after sunset Friday, more likely after midnight for the
Bluegrass region. The highest chances over the entire area come
overnight Friday into Saturday morning as a surface low tracks from
TN into the Great Lakes. Right now between 1/2 and 1 inch of rain is
expected with this system.

In its wake, the trend continues for much cooler air to surge down
across the area for Saturday and Sunday nights. Model consensus
remains about the same from the previous forecast cycle showing lows
in the lower 30s with some upper 20s possible in the rural, colder
spots. Areas of frost was maintained in the forecast.

Heading into early next week, the upper level flow attempts to
become more zonal allowing a moderation in temperatures closer to
near normal with dry conditions at this time.


.Aviation...(06Z TAF Issuance)
Issued at 1245 AM EDT Tue Oct 24 2017

Surface and upper trofiness will dominate the upcoming TAF period,
with intervals of precip and gusty winds at times, but prevailing
VFR ceilings and visibilities.  Strongest vort lobe is swinging
through the trof over Indiana at this hour, and will bring precip
through all the TAF sites overnight, though it will be a close call
in BWG. Rain is light enough not to restrict vis, and is falling out
of a mid-level deck in many locations. Expect ceilings no worse than
FL050-070 overnight. May opt to limit precip mention to VCSH in BWG.

Expect this disturbance to clear the area before daybreak, with deep
and cyclonically curved westerly flow developing. Sustained winds
will pick up to around 15 kt, with plenty of 20-25 kt gusts.
Ceilings should remain VFR in a fairly mixy environment.

Winds should die down in the evening, but do not expect ceilings to
scatter out. Some build-down is possible, especially in LEX and HNB,
but even there the worst case is high-end MVFR. Current forecast
will ride with VFR ceilings, but this bears watching in later TAF




Short Term...ZT
Long Term...ZT
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