Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 290704
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
304 AM EDT Fri Aug 29 2014
.SHORT TERM (Now through Saturday)...
Issued at 300 AM EDT Fri Aug 29 2014
Weak frontal boundary is roughly located along our southern border
this hour. This boundary is forecast to lift northward today, with a
wind shift from easterly ahead of it to southerly behind it. Lift
along this front as well as instability from late afternoon heating
should produce isolated to scattered storms, with the best chance
over southern Indiana and the Bluegrass region of Kentucky. The
stronger storms will produce brief gusty winds and heavy rain.
Those storms should exit to the northeast this evening before
another round comes in from the west late tonight. This action will
be as a low-level jet aids in development over the Bootheel region
that will shift eastward toward daybreak. Precipitable water values
will climb to near 2 inches during the day. The main focus for
heavier storms will be along another front to our northwest, but any
heating over our region should be able to produce scattered storms.
The main problem with these storms will be the torrential rainfall,
given the high atmospheric moisture. Storm motion vectors indicate
enough motion that we should be able to avoid flash flooding, but
areas that receive multiple rounds of storms could see some minor
flooding, especially in poor drainage areas.
Temperatures will continue above normal this period.
.LONG TERM (Saturday Night through Thursday)...
Issued at 300 AM EDT Fri Aug 29 2014
...Unsettled Weather Through the Holiday Weekend and into Next Week...
Multiple rounds of shower and thunderstorms are expected through the
long term with storms likely for a portion of the holiday weekend. A
weakening upper level trough will cross the upper Midwest Saturday
and move into the Great Lakes region by Sunday morning. Another
vortmax will track northeast through the upper level flow and into
the Lower Ohio Valley Saturday night into Sunday. At the surface
southerly flow will remain in place with high pressure centered off
the east coast.
The best chance for showers and storms during the long term will be
right at the beginning on Saturday night and Sunday as the upper
level disturbances move through the area. Wind fields are not overly
impressive, but a few strong storms will be possible with gusty
winds. However, soundings do reveal a very saturated atmosphere with
PWAT values rising to over 2 inches. Long skinny CAPE is also
suggestive of very heavy rain. Storms should be moving somewhat
quicker than previous episodes of heavy rain we have seen this
month. However, given torrential rainfall potential from storms, if
there is any training some minor flooding issues will be possible.
This would particularly be a concern in urban areas.
Another vortmax will set off another round of showers and storms
Monday afternoon. With drier air filtering in at mid levels PWATs
will drop Monday and heavy rainfall should be less of a concern. By
Tuesday a frontal boundary will drop south towards the area from the
north. This boundary looks to get hung up north of the forecast
area, though the models do have some differences in the details
towards the end of the forecast period. Regardless, scattered
showers and storms will be possible through Thursday along and south
of this front.
Temperatures for the most part will be in the mid 80s to lower 90s.
The exception will be Sunday. With all the clouds and precipitation
in the area temperatures will top out in the lower to mid 80s. Lows
will be in the upper 60s to lower 70s.
.AVIATION (06Z TAF Update)...
Issued at 115 AM EDT Fri Aug 29 2014
First concern is fog formation down at KBWG early this morning.
Already have MVFR conditions now, and vsby trend forecasts give a
good shot at IFR if not LIFR by daybreak. Bust potential could come
from a deck of clouds along the KY/TN border this hour, so will have
to see if that maintains itself on the way to the terminal.
KLEX did not get rain today, and consequently, the vsby is still at
10 miles this hour. With a solid east wind, have backed off on fog
potential there and gone with a tempo group for a few hours around
Next up will be dealing with scattered storms forming as a warm
front lifts north across the region today. The best chance for
development will be where this front coincides with peak heating.
Think this will happen over the Bluegrass later this afternoon. Have
enough confidence to go Prob30 for now, even though statistical
guidance is low. Cannot rule out development near KSDF, but think
chances are just a bit lower there so kept it out for now.