Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 170113
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
912 PM EDT SUN JUN 16 2013
Issued at 911 PM EDT Sun Jun 16 2013
Precipitation continues to push into eastern KY this evening. With
the quickly diminishing instability and the main forcing exiting the
region, think much of the overnight hours will be dry. Will keep a
slight chance of a shower towards morning as another shortwave
trough slides through the zonal flow aloft, but coverage will remain
limited. Am a bit concerned about some fog (possibly rather dense)
tonight, especially across areas that received heavy rainfall
today. Winds will go rather light, but lingering cloud cover might
hinder what otherwise would be a very good fog setup. Will just
enter areas/patchy area of fog into the grids for now, and allow the
overnight shift to monitor the situation. Will also enter the fog
potential into the HWO. Updated products will be out shortly.
.SHORT TERM (Fathers Day through Monday Evening Night)...
Issued at 300 PM EDT Sun Jun 16 2013
Well...I have primarily focused on POPS and weather to hone on best
opportunities for pcpn. 1st wave of pcpn is ahead of a cold front
located from BMG to MVN. Meanwhile warm sector pcpn developing in
better instability acrs S Central KY. Storms acrs the S have 1500
j/KG to work with with deep moisture plume above. These will make
for a few gully washers with some gusty winds below.
The main area of precip is moving to the E-SE and will bring likely
to categorical pops acrs S IN and N Central KY later afternoon
through mid evening. The NAM is handling the pcpn initialization
quite well and moving pcpn filed to the SE makes sense. The GFS is
much more aggressive. The high resolution models are all over the
place over the next 18 hours with the ARW, HRRR, SPC WRF etc all
having various solutions with the wx scenario. Overall, have cut
back pops tonight in all except Sr Tier counties.
The cold front currently located from Lake Erie to near STL will
slide SE tonight to SRN IN by 12z Monday. Model soundings show low
level clouds encompassing the Srn IN counties Monday morning, so
have cut back pops significantly with except of the srn tier again
where better instability and moisture exists.
On Monday, took the POPS out of SR IN in the morning and then with
ill defined front nearby have slgt chc of storms in the afternoon.
For the S KY counties coordinated with PAH and have high end chance
pops to low end likely pops with better MUCAPE and theta e
advection. The POPS will increase as the day moves along especially
across SW CWA.
Made minor tweaks w.r.t. temps, except for Monday where I decreased
high temps due to cloud cover. MOS guidance has upper 80s and with
cloud cover mid 80s looks more realistic.
.LONG TERM (Monday Night through Sunday)...
Issued at 300 PM EDT Sun Jun 16 2013
Monday Night through Tuesday...
Forecast confidence is not what it was just 12 hrs ago, but still
looks like a period of unsettled weather Monday night through at
least Tuesday as two impulses will sweep through in the cyclonically
curved flow aloft. Confidence is limited by uncertainty in the
timing of these disturbances, and the deeper moisture being
suppressed just to our south.
Will begin Monday evening with likely POPs across the southern tier,
tapering down to slight chance in southern Indiana. Precip chances
will expand northward later in the evening as the upper disturbance
scoots through. Best chances will be a few hours either side of
midnight, in line with the GFS solution which is a bit more robust
than the NAM and slower than the ECMWF. Still not too excited about
severe weather given weak dynamics and instability that is marginal
at best, but a juicy atmosphere will support heavy rainfall as the
One more shortwave to swing through on Tuesday, so the POPs will
continue as the moisture lingers. Slight chance over Indiana, but
40-50 POP from the southern tier up into the Bluegrass region where
there is more juice to work with.
Diurnal temp ranges will be limited by clouds and moisture. Min
temps split the difference between model guidance numbers, while
highs will be on the low end of consensus.
Tuesday night through Sunday...
Surface high over the Great Lakes and upper ridge building from the
southwest will bring drier weather with temps near climo and lower
humidity on Wednesday and Thursday. Warmer and more humid air will
return later in the week as southerly low-level flow develops and
the upper ridge continues to build in from Texas. Temps will push 90
Friday through Sunday, with lows either side of 70. With the ridge
axis extending more into the Mississippi Valley, there remains the
possibility for convection to fire to our north and west, and move
into the Ohio Valley as it decays. Therefore will go with a somewhat
broad-brush 20 POP for a lot of the weekend.
.AVIATION (18Z TAF Update)...
Issued at 650 AM EDT Sun Jun 16 2013
Well...the pcpn has moved out of SDF...SHRA in the VCNTY for another
hour or so at BWG and at LEX shra and isol tsra at the airfield for
another 1-2 hours. The heavy precip in the LOU metro and near calm
wind will bring some fog. The same goes for LEX, although they may
receive less pcpn than SDF. In addition the low clouds over IN/IL
will descend down along the front. Have 3000 ft BKN in the morning
at LEX and SDF.
Convection on Monday is less clear, with low clouds perhaps
inhibiting the north in the morning while KY will be less unstable
than it was on Sunday. The 12z models have pushed most of the pcpn
south of the airports, so we will look at the 00z runs for more
info. For now have the best chances of storms acrs the BWG airport
with VCNTY of SHRA for the moment.