Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 301849

249 PM EDT Thu Oct 30 2014

.SHORT TERM (Now through Friday Night)...
Issued at 245 PM EDT Thu Oct 30 2014

...Windy Conditions and Falling Temperatures Expected Friday...
...Chance for First Snow of the Season Increasing Friday Night...

Have several systems to deal with in this period. The first is a
shortwave, evident on water vapor over western Iowa, that will dive
into the Tennessee Valley tonight. This system looks to have enough
moisture associated with it to produce at least scattered light rain
showers mainly after midnight tonight.

Another upper disturbance, this one stronger, will drop from the
Great Lakes Friday afternoon and evening. A front will pass through
our region just ahead of this feature, ushering in much cooler air
behind gusty northwest winds. By Halloween late afternoon, expect
winds to gust to 25-35 mph. The center of the upper low is forecast
by model consensus to be over the eastern KY mountains by 06Z
Saturday. Isentropic analysis at 285 and 290K indicates a trowal
wrapping around this upper low bringing a good chance for banded
precipitation early Saturday morning. Forecast soundings would
indicate a lot of this precip could fall as snow. Forecast
temperatures would support it as well, but accumulations will depend
on how heavy the snowfall is. Ground temperatures are too warm to
keep this snow for very long, so if it falls slow enough it will
just affect visibilities.

Speaking of those ground temperatures, forecast lows will be around
freezing Saturday morning. Normally we would not issue a freeze
watch for forecast lows right down to around 32, as local policy is
to have temperatures to or under 30 for at least a couple of hours.
However, given this is the first widespread chance to reach
freezing, and in collaboration with neighboring offices, we will go
ahead and hoist a freeze watch for early Saturday morning and extend
add a second headline for the more solid freeze Sunday morning, read
long-term discussion below.

.LONG TERM (Saturday through Thursday)...
Issued at 245 PM EDT Thu Oct 30 2014

...Sub-Freezing Temperatures Likely Sunday Morning...

The synoptic pattern at the start of the long term period will
feature an abnormally deep/strong trough across the eastern CONUS,
with an upstream ridge across the central United States.  This
regime will deamplify through the period, making for a warming trend
through the period as the large trough breaks down.

The cold core of the upper-level trough will be pushing east of the
Ohio Valley by Saturday morning.  Therefore, any lingering light
snow showers (see short term section above) will be pushing east of
the I-75 corridor.  However, forecast soundings suggest low-level
clouds will hang around through much of the day across areas east of
I-65 on Saturday.  Given the surface cold-air advection coupled with
the lingering cloud cover, think temperatures will really struggle.
Have knocked them down a couple of degrees across the Northern
Bluegrass, as highs will likely struggle to make it out of the upper
30s and lower 40s.  Further west, some sunshine looks a bit more
likely, thus will forecast highs in the mid and upper 40s.  Either
way, Saturday is shaping up to be quite a raw fall day across the
Ohio Valley.

The coldest temperatures of the season thus far will be felt
Saturday night into Sunday morning, as a strong surface ridge
settles into the Ohio Valley.  Pretty high confidence exists for a
widespread freeze early Sunday morning, as temperatures dip into the
20s across most locations which should put an end to the growing
season.  Thus, have issued a Freeze Watch for Sunday morning (in
addition to Saturday morning).  The only potential bust in these
temperatures would be cloud cover lingering near the I-75 corridor,
but it appears these clouds will clear quickly enough to allow
temperatures to quickly fall towards morning.

A warmup will commence Sunday into early next week, as upper-level
ridging builds into the Ohio Valley.  Highs Sunday will climb back
into the 50s, with 60s becoming likely Monday into Tuesday.

The next storm system in the form of a slow-moving cold front will
arrive Tuesday night into Wednesday.  PWATs will climb to 1.25-1.5
inches, which will support some moderate pockets of rainfall.
Instability at this long time ranges continues to look meager, thus
will continue to leave thunder out of the forecast for now.


.AVIATION (18Z TAF Update)...
Updated at 115 PM EDT Thu Oct 30 2014

A couple of disturbances will cross the region this TAF period. The
first will bring scattered showers early Friday morning. That chance
should increase by late morning along with lowering cigs. Late in
the period a second disturbance will bring gusty northwesterly
winds, with SDF gusting to 25-30 knots.


KY...FREEZE WATCH from late Friday night through Saturday morning FOR

     FREEZE WATCH from Saturday evening through Sunday morning FOR

IN...FREEZE WATCH from late Friday night through Saturday morning FOR

     FREEZE WATCH from Saturday evening through Sunday morning FOR



Short Term........RJS
Long Term.........KJD
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