Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 280459
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1259 AM EDT Tue Oct 28 2014
...Updated Aviation Discussion...
Issued at 955 PM EDT Mon Oct 27 2014
Forecast appears to be on track overnight into Tuesday. Southerly
breezes are slowing the diurnal cooling, so hourly temps will be
nudged upward for the higher-resolution/point-and-click products.
Min temp forecast may be a degree or two too cool, but not enough to
justify raising mins, so zone forecast will be left as is.
.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 (06Z TAF Update)...
Updated at 1255 AM EDT Tue Oct 28 2014
VFR conditions expected in the near term at the TAF sites with the
main aviation concern being LLWS as strong southwesterly flow exists
across the region. 40 kt winds will persist at the top of inversion
/1000-1500 ft/ through about 12z and with surface winds falling
to around 5-7 kts, LLWS looks good in the forecast. Toward
sunrise, surface mixing will reduce LLWS threat, though 20-25 kt
gusts will then impact the terminals through the morning hours.
Strong cold front that currently stretches from St. Louis
northeastward toward southern Wisconsin will advance toward the
region later today. Expecting low-end VFR strato-cumulus to develop
by mid/late morning, then with sufficient daytime heating, a band of
showers will cross the region. Kept thunder mention out of the TAFs
at this point, as instability parameters do not support higher than
isolated chance, and mainly at LEX. Forecast guidance suggests LEX
would have the greatest potential to experience a thunderstorm with
brief MVFR ceiling/visibility restrictions a possibility.
Precipitation looks to end west to east a few hours on either side
of 00z, first at SDF then likely lingering at BWG and LEX through
about 03z. Winds will become westerly and then northwesterly
toward the end of the TAF period as cold air advection takes over
in the wake of the frontal passage.