Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 312328
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
728 PM EDT Sun May 31 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Monday Night)...
Issued at 240 PM EDT Sun May 31 2015
Mid-afternoon surface analysis showed a compact area of low pressure
centered near Columbus, Ohio with a cold front extending southwest
through portions of eastern and south-central Kentucky. Southwest
breezes in the warm sector allowed readings to rise into the upper
70s to low 80s with summer-like cumulus. Meanwhile, across southern
Indiana and northern Kentucky, northwest flow behind the front and
low clouds have kept temperatures steady in the 60s, even mid to
upper 50s in places. There is a 25 to 30 degree temperature
difference across the forecast area this afternoon.
The main challenge is precipitation chances this evening through
Monday associated with an upper level shortwave trough currently
over Arkansas. The trend in model guidance the past 24 hours is for
this feature to be stronger, further north and to eventually close
off/stall nearby. The current shield of showers and embedded storms
across western TN, eastern AR is expected to slowly lift
north/northeast, running into the more stable air across Kentucky
tonight. Soundings show increasing lift in the low/mid levels after
06z along with deeper saturation. As a result, light rain showers
look to spread north/northeast into the forecast area. Hi-res models
and 31.12z guidance bring the precipitation all the way north to the
Ohio River and into southern Indiana by commute time Monday morning.
As a result, raised POPs to the 40 to 60 percent range for the
overnight into the first half of Monday. This may not be high enough
across central into northern KY, though there remains questions on
how much saturation will take place due to drier northeast flow.
Rainfall amounts generally look to be 0.1 to 0.2. While some
elevated instability is possible this evening across the
south/southeast, expecting predominately just rain showers.
With the increased chance for rain showers and expected overcast
skies, brought high temperatures down several degrees for Monday. It
will be a rather cool first day of June as highs are likely to be
stuck in the 60s. South-central KY near the TN border could break
out of the clouds late in the day to jump into the low/mid 70s,
otherwise expecting an unseasonably cool day. Normal readings are in
the low/mid 80s. As forcing wanes late in the day, showers will
dissipate giving way to a cool night with lows in the 50s.
.LONG TERM (Tuesday through Sunday)...
Issued at 300 PM EDT Sun May 31 2015
Models have come into some agreement on placing an upper low right
over the Tennessee Valley at the start of this period, helping to
keep us in clouds as well as cooler than normal. How thick those
clouds are will have a big effect on high temperatures likely for
several days this week, as the upper low still will move little.
Even a subtle shift to the east over the next few days could mean a
10-degree swing in temps for our western counties. Rain chances are
still uncertain for the same reason, and think the best chances stay
over our southeast through at least midweek.
By Thursday evening, model consensus brings the upper low into the
Appalachians, yet they still try also to bring in some diurnal
showers. Cannot rule these out, especially if we get some assistance
aloft in the form of a deformation band north of the upper low.
Those models then try and move the low into the Southeast U.S. by
the start of the weekend, allowing more of a northwest flow aloft
for us, as well as warmer temperatures. Northwest flows in the
summer are not always dry for us however, and thus will lean towards
climo pops, 20-30% for the next weekend.
.AVIATION (00Z TAF Update)...
Updated 728 PM EDT Sun May 31 2015
Cold front is now situated south and east of the TAF sites,
meanwhile an upper disturbance is postitioned to our west. Expect a
plume of deeper moisture moving into the region overnight, with a
round of light rain showers and lower ceilnigs/visibilities to go
Pretty high confidence that ceilings below fuel-alternate set back
in between 10 PM EDT and 1 AM EDT at the TAF sites. Think ceilings
at least as low as 1500 ft will persist through the night, however
there is enough potential to see drop into the IFR category in the
pre-dawn hours at BWG/SDF to continue mention. This will likely
occur with light rain showers as well so will include the visibility
drop. Most likely times will be around 2-5 AM EDT at SDF/BWG.
Low MVFR or IFR ceilings, along with steady light rain showers, are
then expected through the late morning/midday hours before rain
stops and ceilings begin to improve back into fuel-alternate or even
Timing of all of this happens a couple/few hours later at LEX. Winds
will generally be steady out of the NE during most of this forecast
Fuel-Alternate Ceilings: High
IFR Ceilings: Medium