Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 170517
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
116 AM EDT MON JUN 17 2013
...Updated Aviation Discussion...
.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 (06Z TAF Update)...
Issued at 110 AM EDT Mon Jun 17 2013
Light winds and some scattered mid-level cloudiness will continue
through the mid-morning hours on Monday with very little additional
chances of rain. However, wet grounds will allow patchy fog to
develop during the pre-dawn hours at LEX and even SDF. Do not think
that visibilities will fall below 4SM in urban SDF. However, MVFR
visibilities as low as 2SM are quite possible at LEX from 08z through
Under variably cloudy skies Monday, ceilings will stay well above
the VFR threshold. Scattered showers and thunderstorms will develop,
especially across the south by late morning or early afternoon,
continuing through the evening hours. With the unorganized nature of
these pop-up storms, will not attempt to time any potential
convection to any TAF site.
Winds will be very light during the day on Monday, perhaps becoming
southerly around 5kt during the afternoon hours.