Scientific Forecaster Discussion
fxus63 klmk 131107
Area forecast discussion
National Weather Service Louisville Kentucky
607 am EST Wed Dec 13 2017
..updated aviation discussion...
Short term...(today through thursday)
issued at 255 am EST Wed Dec 13 2017
Low pressure advancing from Minneapolis to Fort Wayne today and to
New York City by tomorrow morning will drag a cold front through
southern Indiana and central Kentucky this evening. Winds will pick
up as the compact cyclone moves by this afternoon and early evening.
The main bust potential should come from the possibility of clouds
limiting mixing, but right now it looks like we'll have enough sun
to help wind gusts reach advisory criteria, especially west of
Interstate 65. After talking with surrounding offices, will go ahead
and hoist an advisory for this afternoon. The strongest gusts will
occur between noon and 4pm CST.
The front itself should be dry, other than perhaps a few sprinkles
from around Madison to Carlisle, thanks to high pressure blocking
the Gulf and most of the precipitation staying to our north closer
to the low.
Given the strong south-southwest winds and low dewpoints, lifted maxt today
several degrees, and still may not have gone warm enough if we get a
good amount of sunshine.
After a breezy night tonight with lows around 30, weak high pressure
building in will provide US with much lighter winds Thursday with
high temperatures only in the mid 30s to around 40.
Long term...(thursday night through tuesday)
issued at 309 am EST Wed Dec 13 2017
The next upper shortwave trough will cross the Great Lakes on Friday
but precipitation will stay confined to our north. The surface
reflection of this system looks relatively weak so we're not
expecting strong surface winds with this one.
A Southeast Ridge will pump up over the weekend as troughing digs
into the plains. The trough will grab a vort Max over northern
Mexico and sling it northeastward into the Ohio Valley. Surface high
pressure shifting from the Mississippi Delta to the East Coast will
supply Gulf moisture. Precipitation type may be an issue Saturday
night depending on how quickly the precipitation moves in and how
much cool air is in place. Sunday, at any rate, will be all rain as
temperatures warm to around 50.
The new week looks to start on a somewhat drier note as the weekend
system pulls away, but, of course, there is some model disagreement
Taking another peek ahead towards Christmas... large scale troughing
digging into the plains will pull cold air down into much of the
country for several days beginning around the 20th or 21st. The
exception to the cold will be in the southeast U.S. Near a
developing downstream upper ridge from Central America to the
western Atlantic. This would put the Ohio Valley in the battleground
between the two air masses roughly during the 23rd-25th time period.
There have been indications of wave crossings around the 23rd and
24th as well.
The eps and GFS are in fairly good agreement with this general
scenario. CPC forecasts hint at this as well, though they are not as
aggressive with the invasion of the cold Canadian air. The
individual members of the gefs keep S in/c Kentucky mostly on the warm,
rainy side of things, but with such a large mass of cold, dense air
just to our northwest it's not out of the question that the leading
edge of the cold air could push farther east than currently
indicated. Something to watch over the coming days.
Aviation...(12z taf issuance)
issued at 607 am EST Wed Dec 13 2017
A cold front will approach the region today with the pressure
gradient tightening as it does. Winds out of the south-southwest will increase
through the morning and become quite gusty this afternoon with peak
wind gusts of 25-35 mph. Winds will shift to westerly after 0z
tonight as the front moves through and then to northwesterly
overnight. Gusts will persist for at least a few hours after the
front passes through.
Skies will be mostly clear this morning with mainly mid and high
clouds over the taf sites through the daytime hours. Lower clouds
will build in tonight with the front, but ceilings look to remain
in...Wind Advisory from noon EST /11 am CST/ today to 7 PM EST /6 PM
CST/ this evening for inz076>079-083-084-089>092.
Kentucky...Wind Advisory from noon EST /11 am CST/ today to 7 PM EST /6 PM
CST/ this evening for kyz023>034-038-045-053-061>063-