Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 291347
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
947 AM EDT Fri May 29 2015
Updated 940 AM EDT Fri May 29 2015
High-res model forecast reflectivity show bands of precipitation
getting started as early as the next hour. Just a little bit of
sunshine would help to provide showers compared to the extensive
cloud cover yesterday that prevented showers until the afternoon.
Coverage should be more widespread than yesterday, but capped it at
scattered (30-50%). Temperatures will vary through the day based on
where those showers/storms popped up, but in general have highs in
the lower 80s.
.SHORT TERM (Now through Saturday)...
Issued at 305 AM EDT Fri May 29 2015
Locations that saw rainfall yesterday may start the morning with
some patchy fog. Fog should quickly burn off after sunrise.
The region will remain in a warm, moist airmass today with a few
upper level shortwaves expected to spark isld-sct convection
throughout the day. Wind profiles will remain supports of multicell
clusters below severe limits. The strongest storms may produce
gusty winds or small hail as a decent amount of CAPE should build
over the region with skies starting out mostly sunny. Precipitable
water values should be between 1.5-1.7 inches which is on the higher
end of climatology for May. This should result in efficient precip
producers with briefly heavy rainfall. High temps should reach the
low to mid 80s today...potentially cooler in spots that see rainfall.
Tonight the convection should cease or become widely scattered in
nature. According to most of the mesoscale models, most locations
will stay dry tonight. Thus, have lowered POPs to 20% for much of
the overnight hours with an increase in POPs just before sunrise
when an upper level shortwave is progged to enter the area. Low
temps will remain mild in the mid 60s to around 70.
Saturday convective activity should pick up around or shortly after
sunrise. Shortwave activity will increase ahead of an approaching
cold front and upper trough. 40-70% cover of showers/storms is
expected for Saturday with the best chances west of I-65. With
slightly better wind profiles and modest CAPE, strong storms with
gusty winds, small hail, and heavy rainfall will certainly be
possible. High temps should range through the lower 80s.
.LONG TERM (Saturday Night through Thursday)...
Issued at 358 AM EDT Fri May 29 2015
The medium range guidance continues to be in general agreement on
the front end of the forecast package. An upper level trough axis
will be approaching the region at the beginning of the period
bringing several rounds of shower and thunderstorms to the region.
Highest potential here will be from Saturday night through about
Monday afternoon. While instability will be generally decent, the
rich/deep moisture profiles look to keep severe weather chances down
a bit. Damaging winds and perhaps an isolated hail threat look like
the main severe weather hazards. However, of more concern will be
the potential for multiple rounds of heavy rainfall with such high
moisture in place. Temperatures during this period will likely be
held down due to clouds and moisture. For this forecast, have stuck
closer to the lower end of the multi-model consensus here with highs
in the lower-mid 70s and overnight lows in the lower-middle 60s.
By late Monday, the upper level trough looks to shift slightly more
to the east. The trough axis will likely be a little slower moving
out than the current model suggest, thus diurnally driven convection
looks likely for Monday and Tuesday afternoons. More breaks in the
clouds look likely for Tuesday which should allow temperatures to
warm into the lower 80s. By Wednesday, the models take the east
coast trough and allow the southern base of the trough to cut off.
The main differences in the models at this point are whether or not
the upper low will retrograde westward toward the MS delta region,
or if it will temporarily stall over the northern Gulf coast and
then head east. The GFS and it camp of ensembles suggest more of
the retrograde solution, while the Op Euro does the latter with a
temp stall and then movement off to the east. While these are
different solutions in regards to the upper levels, both models do
suggest some sort of tropical development off the SE coast by late
week. The moisture from that system may eventually impact our
region later in the week as well.
With regards to sensible weather, given the increasing of heights
aloft and with the cut off to the south, we should see more of a
diurnally driven convection pattern for mid to late week. Coverage
of precipitation looks to be scattered each afternoon. Temperatures
look to warm a little bit as the week goes on with afternoon highs
in the mid 80s and overnight lows in the upper 60s to around 70.
Total QPF amounts for the week still look rather decent with both
the GFS and Euro runs putting out 2-3 inches. The GFS solutions
seem to be a bit overdone in both coverage and amounts, with the
Euro solutions looking more realistic. Still think there is
potential for some localized hydro issues early in the period with
heavy rainfall and the possibility of locations seeing
repeated/training of storms. This will be something to keep an eye
on in later forecasts.
.AVIATION (12Z TAF Update)...
Updated 650 AM EDT Fri May 29 2015
Some light fog/low stratus will be possible at the TAF sites this
morning. Any restrictions should remain in the high end MVFR
category and be brief.
Isolated to scattered showers/storms will again be around throughout
the day today and will include in the TAF sites with reduced flight
conditions possible in convection.
Winds will range from E to S early this morning remaining under 7
kts for most of the early morning hours. Winds will increase to 8
to 12 kts for the daylight hours today becoming predominantly SSW.