Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 272319
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
719 PM EDT Mon Oct 27 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Tuesday Night)...
Issued at 322 PM EDT Mon Oct 27 2014
...Strong Thunderstorms Possible Tuesday Afternoon Across Central
and Eastern Kentucky...
Early afternoon satellite imagery and observations reveal partly to
mostly sunny conditions across southern Indiana and central
Kentucky. Temperatures have warmed into the upper 70s to the lower
80s and afternoon maximum temperature readings will likely top out
in the next hour or so. It does not appear that we`ll hit record
highs at Bowling Green, Frankfort and Lexington. We have tied the
record at 84 at Louisville and will have the chance to break it in
the next 30-60 minutes if the sun stays out a little more.
Mostly clear skies are expected for this evening with temperatures
falling into the the lower-mid 70s. A stiff southwesterly wind will
continue this afternoon and evening and continue into the overnight
hours. Clouds will be on the increase late tonight as a cold front
approaches from the northwest. Overnight lows will be rather mild
with readings falling into the 60-65 degree range.
For Tuesday, a cold front will approach the region from the
northwest during the morning hours. Showers and a few isolated
thunderstorms will develop in advance of the front to our
northwest. These will spread southeastward during the morning
hours. Out ahead of these storms, we should see some
destabilization of the atmosphere. The high resolution NCEP models
and our local WRF-ARW agree that we should see some pockets of
instability develop during the early afternoon. Model proximity
soundings are not particularly impressive with mid-level lapse
rates, but good moisture transport should result in surface based
CAPE values rising to 500-1000 J/Kg. A strong mid-level flow of
55-60kts combined with slab-forced ascent along the frontal
interface should result in a steady increase in organized
thunderstorm activity. The area of most concern would be those
areas east of I-65 in central Kentucky and over into our Bluegrass
region. Conceptual models would suggest multi-cellar convection
with the potential for upscale growth into bowing line segments
capable of damaging winds. These storms are expected to weaken as
we head into the evening hours. Total rainfall amounts of one to
three quarters of an inch can be expected. Highs will occur ahead
of the frontal passage with readings topping out in the upper 60s to
the lower 70s.
For Tuesday night, we expect winds to shift to the northwest and
temperatures will fall into the 50s with showers ending from west to
east during the overnight hours. Overnight lows look to cool into
the middle 40s across the north with upper 40s to around 50 across
the central and southern sections.
.LONG TERM (Wednesday through Monday)...
Issued at 326 PM EDT Mon Oct 27 2014
Wednesday through Thursday...
Upper air pattern will be characterized by a shortwave trough
digging through the mean NW flow aloft at the start of this forecast
period. Will continue previous forecast thinking of leaving some
lingering small rain shower chances in the far east Wednesday
morning. Otherwise, surface high pressure builds into the area
keeping things dry. Highs will struggle on Wednesday under cold air
advection and an overall cooler airmass, only topping out in the
upper 50s and low 60s. Expect lows in the upper 30s Wednesday night
under good radiational cooling conditions. Thursday highs will be
similar to Wednesday, perhaps a degree or two cooler.
Thursday Evening - Friday...
A quick one-two punch of disturbances will pass through the continue
NW flow aloft to end the week. The first will be Thursday evening,
where just enough moisture will be present to squeeze out a few
showers. Will continue only small chance mention for this time
period. There will likely be a brief lull in any precipitation
chances early Friday morning, before another more potent wave swings
through Friday afternoon. The best forcing and moisture will mainly
stay across our north and east CWA so will continue to carry only
small chances for measurable rain during this time.
Will quickly go dry across our east by later Friday evening as
deeper moisture is carried east. Highs Friday will be another few
degrees cooler, with our NW zones likely seeing falling temperatures
in the afternoon hours.
Friday Night - Sunday Morning...
A more impressive cold shot still looks on tap for the weekend as a
strong continental polar airmass of NW Territories origin quickly
slides south into the Ohio Valley. Expect highs only in the upper
40s to around 50 on Saturday. The bigger story will be lows Saturday
and Sunday mornings. Expect to see lows in the 30 to 35 range by
Saturday morning, however a bit reluctant to go cooler just yet as
steady surface winds may keep the lower levels mixed enough to get
many readings into the upper 20s. Feel more confident that our
eastern zones will have a better shot at upper 20s on Sunday morning
as the surface high center will be just to the east and surface
winds will be much calmer. Either way, some sort of Frost/Freeze
headlines appear to be increasingly likely for the weekend for at
least part of our forecast area.
Sunday - Monday...
A classic moderating/warming trend pattern will take hold for later
Sunday into Monday as we find ourselves on the back side of surface
high pressure and upper ridging aloft. The resultant warm advection
and increasing heights/thicknesses will result in highs in the 50s on
Sunday and 60s on Monday. Lows Monday morning will still be chilly
in the upper 30s to low 40s.
.AVIATION (00Z TAF Update)...
Updated at 715 PM EDT Mon Oct 27 2014
SSW wind gusts should slack off around sunset, but expect a steady
south wind around 10 kt through the night. VFR conditions with LLWS
becoming the main concern as the low-level jet develops by about 03Z.
Expect 40 kt winds at the top of a sharp inversion, somewhere
between 1000-1500 ft.
Cloud cover will be mainly cirrus through the night, but by
mid-morning expect a VFR strato-cu deck to develop, with wind gusts
increasing to around 20 kt as the low-level jet starts to mix out.
Cold front will drop SE across Kentucky during the afternoon, with
most of the rain along and a bit behind the front. There is the
potential for a more convective leading edge, but confidence is not
high enough to include thunder at this time. MVFR ceiling and/or
visibility also likely at some point, but not expected to go
prevailing and timing is too uncertain for a TEMPO.
Wind gusts will diminish in the immediate vicinity of the front,
with a veering to WSW as the precip moves in. Front should be
progressive enough to bring an end to the precip at SDF just before
sundown, but will be too close to 00Z for BWG or LEX to shut off
before the end of the valid TAF period.