Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 251035
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
635 AM EDT Sat Oct 25 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Sunday)...
Issued at 300 AM EDT Sat Oct 24 2014
Latest wator vapor imagery combined with 500 mb heights shows broad
ridging across the southern and central Plains while a weak
shortwave trough is pushing through the Great Lakes region. At the
surface, a cold front lies across northwest Illinois, which is
slated to pass through the forecast area later today. Southerly flow
out ahead of this front has kept temperatures mainly in the middle
to upper 40s with some of the sheltered, cooler spots dipping down
into lower 40s. Patchy light fog has developed across southern and
southeastern Kentucky thanks to a light surface wind field.
For today, there is good agreement between the 25.00z guidance in
regard to the frontal passage, which is expected to pass through
mainly dry. Forecast soundsings show the greatest moisture resides in
the 950-850mb layer, where some weak lift also is found. While the
deterministric models are dry, some of the hi-res solutions /HRRR
and NMM-East/ show what would likely be sprinkles moving across
southern IN and northern KY by mid-morning. Not confident in the
extent of this solution, so have continued dry forecast but could
not rule out a brief sprinkle or two. Mostly cloudy skies this
morning will give way to partly to mostly sunny skies later this
afternoon as the front moves through and drier air builds into the
region. Despite the early cloud cover, high temperatures look to
reach the lower to middle 70s and overall it will be a pleasant late
October day. Plan on mostly clear skies and seasonable low
temperatures tonight, in the upper 40s to near 50 degrees.
Northwesterly flow aloft on Sunday with high pressure at the surface
will result in another mostly sunny day with slightly above normal
temperatures. The forecast area will be within a 850 mb temperature
gradient, with the southwest areas likely to reach the middle/upper
70s while the northeast region near 70 to lower 70s.
.LONG TERM (Sunday night through Friday)...
Issued at 314 AM EDT Sat Oct 25 2014
Shortwave ridging Sunday night and low atmospheric moisture will
keep skies mostly clear. At the surface high pressure will be
edging off to the east, putting us in weak return flow by morning,
which will help keep overnight temperatures up. Lows by Monday
morning should range from around 50 in the Blue Grass (upper 40s in
the usual cool spots) to the middle 50s west of I-65.
Monday will be a pretty amazing day with sunshine and southwest
breezes taking temperatures into the 80 to 85 degree range, courtesy
of deep southwesterly flow between ridging to the east and a surface
cold front and upper trof approaching from the west. Lows Monday
night should be around 60 in the warm regime.
Record Max for Oct 27 Record Warm Low for Oct 28
Louisville 84 (1940) 64 (1991 and 1984)
Lexington 87 (1940) 64 (1984)
Bowling Green 87 (1919) 65 (1984)
Frankfort 89 (1940) 61 (1899)
The aforementioned front will enter the picture Tuesday. Models
have had a hard time pinning down the timing of this front, but
after looking at the past several runs of the GFS plus the EC and
GEM, as well as GEFS plumes, it seems a fropa somewhere around
Tuesday evening is likely. The recent trend of the models to speed
up the front, after previous runs over the past few days tried
slowing it down, may be an aberration. Regardless, we`ll have
increasing rain chances through the day Tuesday, peaking late
Tuesday afternoon into Tuesday evening, and then decreasing towards
Wednesday morning. The best dynamics will be to our north with this
system, but we should still have enough instability and shear for
some thunderstorm development. Depending somewhat on just how much
sun we get Tuesday, southwest winds could gust into the 20-25mph
range by afternoon. High temperatures Tuesday will also depend on
clouds and rain, but right now will go for 70s in the forecast. Lows
Tuesday night will range from the mid 40s in southern Indiana to
lower 50s around Lake Cumberland.
Wednesday and Wednesday night are looking generally dry as high
pressure moves through. Look for highs in the lower 60s and lows in
the lower 40s.
An upper level disturbance will slide overhead Thursday
afternoon/evening, but will be starved for moisture so will keep
PoPs very low.
The new ECMWF has come in with a radically new, wet, solution for
Friday, but it`s much too soon to jump on that so will stick with a
dry forecast (in line with the GFS) for Friday.
Thanks to ILN, JKL, and OHX for coord.
.AVIATION (12Z TAF Update)...
Updated at 634 AM EDT Sat Oct 25 2014
As a cold front approaches the region later today, broken ceilings
in the 3-5 kft range will pass over the TAF sites, clearing out by
the early/mid afternoon hours. No precipitation is expected with the
frontal passage, but plan on a wind shift to the west then
eventually northwest by this evening. As cool Canadian high pressure
builds in late tonight, fog becomes a concern at BWG and LEX.
Soundings show light winds at the surface through about 3 kft by
early Sunday morning and guidance is hinting at fog restrictions.
For now, confidence is high enough to include MVFR visibiities at
BWG/LEX but BWG may end up IFR or worse based on some of the latest