Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 132034
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
334 PM EST SAT FEB 13 2016

.SHORT TERM (Now through Sunday Night)...
Issued at 333 PM EST Sat Feb 13 2016

...Accumulating Snow Likely Sunday into Sunday Night...

An upper wave will move overhead, bringing widespread precipitation
to the region Sunday and Sunday night. Snowfall rates will likely
start out slow in the morning, with only minor accumulations, if
any.

During the afternoon and evening hours the snow should increase as
we get under the right entrance region of the upper jet. Soundings
show high RH near the warm end of the dendritic growth zone while
temperatures and wet bulbs at the surface remain slightly below
freezing.  850-700 Fn convergence will increase significantly, with
the strongest frontogenesis and best moisture supply over Kentucky.
Mid-level lapse rates increase enough to suggest mesoscale banding
will be possible. Slightly negative EPV aloft co-located with high
RH and on the warm edge of the DGZ, with surface temperatures of 25-
30, also support heavier snow with large, wet flakes.

This all easily supports issuing an advisory, which, after
collaboration with neighboring offices, we have done. In
general,right now it looks like amounts of 1-3" north of I-64 and 2-
4" south of I-64 are reasonable. The mesoscale banding suggests that
we could see a few amounts higher than 4", primarily east of I-65
and south of the Blue Grass Parkway. However, coverage and
confidence aren`t enough for a watch yet. WPC shows the chance of
=>4" as being less than 50%. If confidence increases in warning
level snowfall, then a headline upgrade can be issued.

After the snow Sunday into Sunday evening, temperatures will begin
to rise Sunday night ahead of the next system that will move through
early in the long term. Also, Sunday night we will begin to lose
moisture aloft where temperatures are cold enough for snow
production, especially across southern Indiana and north central
Kentucky. While there may be some seeder-feeder assistance from a
shallow layer of higher clouds at first, it looks like glaciation
will reduce significantly overnight. So, a transition to drizzle or
light rain will be possible, beginning in the Bowling Green region
towards midnight and working its way northeastward, reaching just
shy of the Louisville and Lexington areas by daylight Monday
morning. It`s possible we may see a brief period of freezing drizzle
during the transition, but it shouldn`t have much impact as warm air
quickly brings surface temperatures and wet bulbs above freezing.

Temperature wise, we`ll have another cold one tonight as the mercury
drops into the teens. A few single digit readings will be possible
in the northern Blue Grass and the usual cold spots. Highs on Sunday
will range form the mid 20s in the Blue Grass to around the freezing
mark southwest. As mentioned previously, temperatures will climb
Sunday night, with the entire LMK CWA in the 30s for sunrise on
Monday.

.LONG TERM (Monday through Saturday)...
Issued at 331 PM EST Sat Feb 13 2016

An upper shortwave trof will approach on Monday and move overhead
Monday night, while surface low pressure passes by to our south. The
light precipitation late Sunday night will get reinvigorated as we
experience strong upper divergence under the right rear quad of the
upper jet. 700-500 frontogenesis will increase significantly in
conjunction with deep moisture, especially in the afternoon and
evening over eastern Kentucky, along with strong Q-vector
convergence ahead of PVA in the base of the approaching upper trof.

Surface wet bulbs will be above freezing all day in Kentucky, and
near freezing in southern Indiana. Going with a middle-of-the-road
solution (on a very wide road) for MaxT Monday gets us into the 40s
areawide. So, it looks like the transition to liquid that began late
Sunday night will continue into Monday morning, with everyone seeing
plain rain Monday afternoon. Given instability parameters and
general synoptic set-up, mesoscale banding appears less likely
Monday than Sunday.

Sunday night incoming cold air will change the precipitation back to
light snow as it tapers off. No significant accumulations are
expected either before the transition Monday morning or after the
transition Monday night.

A clipper will then shoot through the area Tuesday
afternoon/evening. This will bring a mix of light rain and snow to
the region. Will simply use surface temperatures to determine
ptype in the grids for now.

High pressure will dominate Wednesday-Thursday with dry weather. No
Arctic cold, though, with highs Tuesday in the 40s and Wednesday in
the 50s.

A storm system will then barrel through the Great Lakes Friday and
Saturday and will bring a chance of showers to the region. Thunder
looks unlikely at this time. Highs on Friday will be in the 60s, and
in the 50s Saturday.

&&

.AVIATION (18Z TAF Update)...
Updated at 1155 AM EST Sat Feb 13 2016

Will remain VFR for most of the valid TAF period, with snow holding
off until after daybreak Sunday, and even then the impact will be
initially minimal.

Expect diminishing north winds this afternoon with unrestricted
ceilings. Typical warm advection regime takes hold tonight, with a
mid-level ceiling developing by late evening. Initial onset of snow
still on track for mid-morning, perhaps an hour or two faster than
previously advertised. However, we should remain VFR until after 18Z
Sunday. Look for deteriorating conditions in the planning period at
SDF as the snow picks up in intensity, with IFR ceiling and
visibility developing by mid-afternoon.

&&

.LMK Watches/Warnings/Advisories...
KY...Winter Weather Advisory from 7 AM EST /6 AM CST/ Sunday to 10 AM
     EST /9 AM CST/ Monday for KYZ028>043-045>049-053>057-
     063>067-074>078-081-082.

     Winter Weather Advisory from 4 AM EST /3 AM CST/ Sunday to 7 AM
     EST /6 AM CST/ Monday for KYZ023>027-061-062-070>073.

IN...Winter Weather Advisory from 7 AM Sunday to 10 AM EST Monday for
     INZ077>079-090>092.

     Winter Weather Advisory from 4 AM EST /3 AM CST/ Sunday to 7 AM
     EST /6 AM CST/ Monday for INZ076-083-084-089.

&&

$$

Short Term........13
Long Term.........13
Aviation..........RAS


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