Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 130501

Area Forecast Discussion
National Weather Service Louisville KY
1201 AM EST SAT FEB 13 2016

...Updated Aviation Discussion...

...Forecast Update...
Updated at 820 PM EST Fri Feb 12 2016

Scattered snow showers are moving across southern IN and north
central KY this evening along and ahead of the cold front. Most of
this activity is fairly light, but visibilities could be reduced
somewhat in a few of the more moderate showers. Added in low pops
across the northern half of the region this evening to account for
the showers. These are not expected to produce much, if any,
accumulation. Temperatures have been holding fairly steady this
evening, but colder temperatures are right on the doorstep and will
build in quickly once the do start moving in.

.SHORT TERM (Now through Saturday Night)...
Issued at 300 PM EST Fri Feb 12 2016

One more wave droping down over Indiana this hour may enhance the
chances for isolated snow showers over our Bluegrass region late
this afternoon and evening, but with it coming at a time when the
deepest moisture has departed the region not expecting much more
than another tenth or two of an inch of snow out of these showers.
After that we should stay dry until right at the end of the short
term, 12Z Sunday, as gentle isentropic lift helps to start
generating some light snows over our western counties.

With enhanced northwest winds this afternoon and evening expect
colder air to filter into the region. Wind chills Saturday morning
should drop to around 0 as lows drop generally into the lower teens.
Northwest winds will weaken a little during the day Saturday, but
even with some sun during the day, expect highs only to reach the
lower 20s, perhaps not out of the teens along and north of the I-64
corridor. Saturday night, expect the surface high behind this cold
air mass to be shifting by to our north and, given this proximity,
winds should be mostly calm through the night. Cloud cover in
advance of the lift later that night will be the determining factor
in just how cold it gets. For now have gone with the lowest readings
in our northeast, ahead of the clouds.

.LONG TERM (Sunday through Friday)...
Issued at 300 PM EST Fri Feb 12 2016

...Advisory-level Snow Forecast for Sunday...
...Still Some Potential for a Winter Storm Monday Through Tuesday...

That isentropic lift gradually should strengthen across our region
through the day Sunday. Combined with increasing moisture as well,
as the flow aloft becomes more zonal and surface flow switches
around to southerly, we should see snow rates pick up as the day
goes along. Some enhancement should come too from a shortwave moving
across the Midwest during the afternoon. All that said am going with
snow totals Sunday through Sunday night of 2 to 4 inches. There is
pretty good confidence in this solution, given model trends and
convergence towards this thinking.

Confidence in a winter storm for Monday is lowering. 12Z model
guidance continues the trend of throwing the worst of this storm
just south of our region. Ensemble spreads in the SLP and flow aloft
are very high, indicative of plenty of model disparity.
Deterministic models are a little more unified then the GEFS/SREF
counterparts though. The latter group indicate surface flow more
from the south/southeast with flow above the surface also getting
more of a southerly component. We should stay below freezing through
Sunday night, but may start to creep some above freezing temps along
the KY/TN border around daybreak. GFS soundings show we may briefly
lose ice crystals aloft around daybreak as well, so we could just
have more of a changeover from snow to drizzle, with little in the
way of mixed precip...but still to early to rule that out just yet.

As the day continues Monday, most of the model guidance keep our
region under light precip, but the Euro continues to have a sharper
deformation band close to the Ohio River Monday afternoon and
evening. It is in the correct location ahead of the upper trough for
that time period, just not sure why the other models are not picking
up on this band yet. Have not gone with this solution yet, given the
wealth of other models not calling for the band, but something to
watch for.

Kept most of the model blend going from mid week on, as already have
a lot to look at in the short and mid term. GFS/Euro/GEM all show a
clipper middle of the week, but all differ on timing. Given warmer
temperatures, timing during the day would be more rain, whereas at
night it would be snow. Beyond that though the trend is for warmer
weather by week`s end.


.AVIATION (06Z TAF Update)...
Updated at 1200 AM EST Sat Feb 13 2016

Polar frontal boundary continues to push southeastward through the
region.  This feature combined with weak upper level disturbance
will continue to produce scattered snow showers and flurries for the
next few hours.  KSDF and KLEX will see the best chances for snow
showers over the first part of the TAF period.  However, with the
upper air feature moving out and drier air moving in aloft, this
should effectively shut off the snow showers after 13/07-09Z.  Gusty
NW winds will continue at the terminals for the next several hours
until the pressure gradient relaxes later this morning.  Ceilings
and visibilities are expected to remain at VFR or above, though KLEX
could see a brief drop to MVFR between 13/06-08Z with the passing
snow showers.

The outlook for the daylight hours looks good as VFR conditions are
expected at all three terminals with northwest winds of 6-8kts.


.LMK Watches/Warnings/Advisories...


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