Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 281737
Area Forecast Discussion
National Weather Service Louisville KY
1237 PM EST Mon Nov 28 2016
Issued at 1225 PM EST Mon Nov 28 2016
Expanded the Wind Advy north a row of counties into southern
Indiana/northern Kentucky and made the start time a bit earlier
(18Z) with this update. Wind speeds over western and southern KY
are already peaking in the 30-35 mph range. Expect the gusts to
increase as mixing increases this afternoon, the LLJ strengthens,
and the main meso-low approaches KY. Based on the latest high-res
data, feel that gusts around or above 40 mph will be likely over a
large portion of the area.
Issued at 955 AM EST Mon Nov 28 2016
Updated the forecast to adjust POPs with a slightly slower
transition eastward through early afternoon. This adjustment was
based off of radar and the latest high-res data. Forecast highs in
the mid 50s-lower 60s still look on track. The Wind Advy looks good
as well but may need to be expanded north. Will await the 12Z data
and coordination before making a decision.
Issued at 630 AM EST Mon Nov 28 2016
Weak radar returns already showing up over central Kentucky and
southeast Indiana, and even some light rain in a few surface
observations. However, T/Td spreads remain quite large, and ceilings
near 10K feet, so anything that is reaching the ground will take a
long time to add up to a hundredth of an inch. Current forecast POPs
look to be well on track for the day.
Warm advection already well established and temps have recovered
into the upper 40s/lower 50s across the area. Hi-res products will
be updated to better reflect these hourly trends.
.Short Term...(This evening through Tuesday night)
Issued at 315 AM EST Mon Nov 28 2016
...Widespread Rain and Gusty Winds This Afternoon and Evening...
Amplifying pattern ahead of a closed upper low in the Northern
Plains is cranking up a deep southerly flow over the Mississippi and
Ohio Valley. First decent feed of Gulf moisture in what seems like
months is evident by radar returns extending from NE Wisconsin down
through Chicago to Memphis. However, as this precip tries to push
east into Kentucky and southern Indiana, it will take a while to
saturate the low levels, given that T/Td spreads are still near 10
Low-level jetting will translate eastward into central Kentucky as
the day progresses, and precip will progress east accordingly. POPs
ramp up from west to east, perhaps a few hrs slower than previously
advertised. Heaviest rain this afternoon will be along and west of I-
65, and then spreading nito the Bluegrass and Lake Cumberland this
evening. Storm total QPF should exceed an inch west of a line from
Bowling Green to Lexington, with localized amounts pushing 2 inches
especially in southern Indiana. Have included isolated/scattered
thunder mostly out of respect for the dynamics of this system, as
the instability is lacking.
Another concern today will be winds, especially with the strong low-
level jetting across the area. Expecting 925mb winds to crank up to
50 kt, with 850mb winds near 70 kt. Even with next to no
instability, it won`t take much to mix down some strong gusts. Have
collaborated with JKL and OHX to hoist a Wind Advisory for most of
central Kentucky from 21Z to 05Z Tue, with the main focus on
potential for gusts near or just above 40 mph.
Precip shield exits to the east after midnight tonight, and Tuesday
will see quite a mild pattern with SW flow continuing through a
fairly deep layer. Expect dry and unseasonably warm weather, with
temps a solid 10-15 degrees above climo.
.Long Term...(Wednesday through Monday)
Issued at 255 AM EST Mon Nov 28 2016
Next system will take shape quickly along the TX/LA Gulf Coast on
Tue night and lift NE, riding up the spine of the Appalachians on
Wednesday. Plenty of Gulf moisture will stream into the Tennessee
and Ohio Valleys, but with likely/categorical POPs east of I-65 in
Kentucky. Confidence in the north/west extent of this precip shield
isn`t too high yet, but anywhere from a half to 1 inch of rain is a
good possibility in the Bluegrass region and near Lake Cumberland.
Amounts and POPs will taper off sharply west of Interstate 65.
Expect dry and cool weather Wednesday night through Saturday as a
closed upper low moves from the Upper Midwest into the Great Lakes,
and opens the door for some cooler but hardly Arctic air. Temps will
run a few degrees below climo, with enough cloud cover that the
first few days of December will look the part.
Models diverge in the latter half of the weekend with an upper low
ejecting out of the Southwest desert. ECMWF develops a closed low as
it lifts from the Red River Valley into the Great Lakes, while the
GFS holds the main low back over Mexico with any impulses out of it
being suppressed over the Deep South. Will introduce a small POP Sat
night and Sun, but also keep min temps warm enough to avoid
unnecessarily implying a precip type issue as the wet scenario would
also be a warmer solution. Either way, expect enough cloud cover to
limit diurnal ranges, so leaned on the cooler end of guidance for
max temps. Confidence still remains limited given the lack of model
.Aviation...(18Z TAF Issuance)
Issued at 1238 PM EST Mon Nov 28 2016
A strong storm system will quickly ride up the Ohio River Valley
this evening, bringing gusty S winds, periods of heavy rain, reduced
visibilities, and marginal VFR/MVFR ceilings.
Light rain is ongoing beneath VFR ceilings at this hour. In
addition, gusty S or SSE winds will pick up through the afternoon
and evening. Main surge of moisture arrives just after sunset at
SDF/BWG, and toward midnight at LEX. With this surge expect a broken
line of stronger showers, and a possibly a rumble of thunder, to
move through the region. A brief period of IFR visibilities in heavy
rain will also be accompanied by gusty WSW winds between 30 and 40
mph. Expect that ceilings will drop to around the MVFR/MVFR
threshold during this time.
We should quickly return to dry conditions by Midnight at BWG/SDF,
and just after Midnight at LEX. Winds may be variable for a few
hours behind the main precipitation batch, but will return to a
steady SW flow by dawn. The rest of Tuesday (daylight hours) will be
IN...Wind Advisory until midnight EST /11 PM CST/ tonight for INZ084-
KY...Wind Advisory until midnight EST /11 PM CST/ tonight for