Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 141857
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
257 PM EDT TUE MAY 14 2013
.Short Term (Tonight - Wednesday Night)...
Issued at 255 PM EDT Tue May 14 2013
Surface high pressure will continue to shift to the south and east
through the short term as a low pressure system traverses
southeastern Canada. South to southwesterly surface flow will
continue to advect in warmer air. For tonight the atmosphere is
expected to remain somewhat mixy with winds of 10-12 mph through the
night. Thus, despite clear skies, we will not see ideal radiational
cooling. Lows tonight will be much warmer than last night, in the
lower to mid 60s. Winds will become quite gusty once again tomorrow
afternoon. High temperatures look to be a bit warmer tomorrow with
temperatures topping out in the lower to mid 80s areawide.
The front extending from the low in Canada will drop south and stall
out just to the north of the forecast area tomorrow night. Scattered
convection will develop near this boundary. This will affect mainly
southern Indiana and north central Kentucky Wednesday night. Across
south central Kentucky it should be mostly dry overnight with just
some isolated showers or thunderstorms possible towards daybreak
Thursday. Lows will be in the lower to mid 60s.
.Long Term (Thursday - Tuesday)...
Issued at 256 PM EDT Tue May 14 2013
Several shortwave troughs are expected to move overhead during the
long term, with more significant waves around Thursday evening and
Saturday evening. Then, after some brief ridging on Sunday, a more
large-scale upper trough will sweep in from the west early next
week. These features interacting with a warm and moist atmosphere
will raise the possibility of scattered showers and storms.
At the surface, high pressure will remain more or less in place over
the southeast United States. This will have two main effects for
us; one being that it will pump warm and humid Gulf of Mexico air
northward, and another that it will keep surface fronts coming in
from the Plains or Great Lakes from making it very far to the
southeast. This makes for a very challenging forecast, since how
far southeast the surface features make it will have a big say in
how much convection we will see in the Ohio and Tennessee Valleys.
A quasi-stationary front will be draped east-west just north of the
Ohio Valley through the weekend, with occasional forays to the north
and south. This feature will help to focus thunderstorm activity,
including overnight MCS development to our west and north which may
send left-over showers and thunderstorms into our region.
By Monday morning the deeper upper trof will spin up surface low
pressure over the Plains which should pull the stationary front
north. The low will advance into the Great Lakes and eventually
swing a cold front through southern Indiana/central
Kentucky...possibly just after this forecast period...with
additional showers and storms.
It`s still a question if we see any severe weather out of this
pattern. Right now it appears we could see some stronger storms on
Saturday in association with the upper wave and a 5H speed max. The
models develop quite a bit of surface instability but that may be
predicated on any MCS remnant clouds/showers coming through in the
morning. Then, the next best chance for stronger storms would be on
Tuesday ahead of the advancing Plains cold front...though that may
end up holding off until Wednesday.
Highs each day are progged to be around 80, depending on the
prevalence of clouds/storms. Most overnight lows look to be in the
lower and middle 60s.
.Aviation (18Z TAF Issuance)...
Issued at 1245 PM EDT Tue May 14 2013
Surface high pressure will continue to shift southeast of the region
through this TAF period. Winds will be out of the south to southwest
through tomorrow. Gusty winds that have developed this afternoon
will diminish this evening. However, winds are expected to remain in
the 8-10 knot range overnight. Breezy conditions will develop once
again by mid morning tomorrow. Skies will be mostly clear with just
some cirrus beginning to stream in tomorrow.