Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 110708
Area Forecast Discussion
National Weather Service Louisville KY
308 AM EDT SUN OCT 11 2015
.SHORT TERM (Now through Monday)...
Issued at 300 AM EDT Sun Oct 11 2015
Surface high pressure and mid-level northwest flow early this
morning is resulting in mostly clear skies (just some high-level
cirrus clouds) and near calm wind with current temps in the mid 40s
to around 50, close to dewpoint temps. There are two concerns in the
short term - areas of fog over south-central KY this morning, and
precip chances associated with a cold front late Monday afternoon.
Residual surface-based moisture mainly over parts of south-central
KY is resulting in patchy/areas of fog early this morning. Already,
Bowling Green has been less than a mile at times with 2-3 miles at
Glasgow. Moisture is very shallow, meaning that visibility will be
variable ranging from light/no fog to locally dense, especially in
cool valleys. There should be little or no fog over north-central KY
and south-central IN. Any fog over downstate KY will burn off
quickly after sunrise.
For the day today, it will be mostly sunny with again just some high-
level cirrus clouds and a southwest breeze up to 10 mph this
afternoon. High temps will reach the lower to mid 70s, generally
between MET and MAV guidance. Mostly clear skies continue tonight,
with little/no fog areawide.
On Monday, a shortwave trough will dig southeast into the Ohio
Valley. Low-level moisture initially will be scant, but models do
increase precipitable water values to 1.0-1.25 inches in the
afternoon (NAM seems a bit overdone with 1.25-1.5 PWs). Model
soundings show decent lapse rates aloft later in day, with low-
levels marginal. Given forcing associated with the shortwave and
associated cold front, isolated to scattered showers and possibly
isolated thunderstorms are expected in the afternoon into evening
hours Monday across the area. Will keep probabilities tame at this
time, given moisture concerns. If any storms can develop, a gusty
wind or two is possible given a large boundary layer temp-dewpoint
spread. Afternoon temps Monday ahead of the front will rise nicely
into at least the upper 70s and lower 80s.
.LONG TERM (Monday Night through Saturday)...
Issued at 302 AM EDT Sun Oct 11 2015
The cold front and upper trof axis will exit the region by daybreak
Tuesday, with little more than some isolated evening showers east of
I-65 accompanying the system. Temperatures behind the front will
tumble into the upper 40s.
Dry weather can then be expected through at least Thursday. A cold
front will come through on Wednesday but won`t have enough moisture
to work with to generate showers. Winds could get a little gusty in
the afternoon, with high temperatures ranging from the upper 60s in
the Blue Grass to middle 70s around Bowling Green.
Another cold front may then come through late Thursday night into
Friday. The operational ECMWF, JMA, and CMC are showing a chance of
showers with this frontal passage. The GEFS mean also suggests QPF,
though looking at the individual members it appears that most of
them stay dry, including the operational run. The last several GFS
runs have been dry. Even the JMA and CMC only show a very small
chance of precip. The EC may be too robust with its shower
generation, just as it has possibly been to robust with its QPF for
the Monday evening front. Even on the wet EC, its own atmospheric
profiles show little moisture in the column. So, given this, plus
the fact that it is fairly far out in the forecast, and after
collaborating with surrounding offices, will continue with a dry
forecast for Thursday night and Friday for now.
Dry weather will then continue into Saturday as Canadian high
pressure noses in from the northwest. Some light, brief, patchy
frost may be possible around dawn Saturday morning in sheltered
locations in the Blue Grass given current forecast data.
.AVIATION (06Z TAF Update)...
Issued at 125 AM EDT Sun Oct 11 2015
North to northwest mid-level flow will bring some cirrus clouds
across the TAF sites during the forecast period, but that`s about it
cloud-wise. Light/calm surface winds early this morning will become
southwest during the day Sunday from 5-10 kts, then south Sunday
night from 3-6 kts. Conditions will be VFR through the period,
except for areas of fog over south-central KY, including BWG (and
perhaps LEX) early this morning.
Temps overnight will fall a few degrees below the crossover temp at
BWG leading to areas of fog. Moisture is very shallow just in the
surface layer, so vsbys could be variable at BWG early this morning
ranging from 1/2 mile or so (LIFR, and perhaps VLIFR briefly) to
around 2 miles or so (IFR). After sunrise, vsbys will improve
quickly to P6SM. Vsbys at LEX should stay P6SM but could be MVFR at
times toward daybreak. Expect SDF to remain P6SM through the period.