Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 101731
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1231 PM EST Sun Dec 10 2017

...Updated Aviation Discussion...

.Forecast Update...
Issued at 1120 AM EST Sun Dec 9 2017

Forecast this morning remains largely on track. Some minor tweaks
were made to the sky grids to account for some of the mid/high level
clouds we are seeing, as well as upstream clouds in IA/IL/MO that
will move in later this afternoon. Otherwise, still expecting a
breezy and cool afternoon today.

&&

.Short Term...(This afternoon through Monday evening)
Issued at 239 AM EST Sun Dec 10 2017

Latest satellite imagery showed the last of the stratus from
yesterday`s snow event exiting central Kentucky with the remainder
of the area mostly clear. Light westerly winds prevailed and early
morning readings were in the 20s. By daybreak, low to mid 20s will
be common with a few spots dipping into the upper teens.

A quieter weather day is in store for southern Indiana and central
Kentucky as the upper level shortwave energy pivots quickly toward
New England. At the surface, a weak but fast moving clipper will
pass through the Great Lakes region with little to no sensible
weather impacts across our area. Plan on southwest winds gusting
this afternoon into the 20 to 25 mph range, and high temperatures in
the upper 30s across southeast Indiana and the KY Bluegrass to mid
40s across southern Kentucky. Clear and dry weather is expected
tonight with lows in the low to mid 20s.

Another fast moving clipper system will dive into the lower Ohio
Valley Monday afternoon and evening. Ahead of it, strong southwest
winds will usher in warmer air with highs reaching the mid 40s to
lower 50s.

By Monday late evening into Monday night, post-frontal moisture gets
trapped in the lower levels under a strengthening inversion. With
weak lift present in forecast soundings, flurries or light snow
showers will be possible late Monday night into the first part of
Tuesday morning. Soundings also show the potential for a loss of ice
saturation which could mean more of a wintry mix, but for now have
left that out and kept just flurries or snow showers in the
forecast. Lows Tuesday morning will range from the upper 20s to
lower 30s.

.Long Term...(After midnight Monday night through Saturday)
Issued at 240 AM EST Sun Dec 10 2017

Strong cold air advection behind the departing low pressure and
upper level shortwave Tuesday morning will result in a seasonably
cold day as highs struggle to reach the freezing mark. It will also
feel much colder with northwest winds 10 to 20 mph at times making
apparent temperatures in the upper teens to 20s all day. Continued
the mention of light snow or flurries for the first half of Tuesday
morning across the Bluegrass but that should clear out by afternoon.

Clear and cold will be the theme for Tuesday night as readings
bottom out in the teens for most of the area. Wednesday will be
slightly warmer with highs mainly in the 30s.

Forecast confidence drops off Thursday through the remainder of the
period. Overall, the synoptic pattern between the various global
models is similar, continuing the large scale troughing over the
central and eastern US. Differences arise in the timing, strength,
and location of fast moving clippers in the northwest flow. The
10.00z runs of the GFS and ECMWF both show a clipper in the
Wednesday night through THursday evening time frame, but large
differences in strength and location. For now, will carry chances of
snow showers, especially along/north of the I-64 corridor.

Temperatures in this period will vary depending on the track and
timing of the aforementioned systems, but overall at or below mid
December normals look likely.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1225 PM EST Sun Dec 10 2017

VFR conditions are expected this TAF period.  A cold front will push
through the region this evening. Ahead of the front this afternoon,
SW sfc winds of 10-15 kts will gust up to 20-25 kts until around
sunset. This evening, a LLJ of 38-42 kts from the west looks to
develop just head of the front causing some LLWS at BWG/LEX from 23-
5Z.  A weak inversion and sfc winds of 6-8 kts from the SW will be
in place making for a marginal LLWS event. The LLJ should be weaker
and shorter lived at SDF/HNB so did not include LLWS for them. After
the fropa by late evening, winds should lighten and be somewhat
variable during the overnight hours.  Winds will be predominantly
SSW for tomorrow increasing to 7-9 kts by late morning.

&&

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

$$

Update...DM
Short Term...ZT
Long Term...ZT
Aviation...AMS



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