Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 071921
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
321 PM EDT Tue Jul 7 2015
.SHORT TERM (Now through Wednesday Night)...
Issued at 320 PM EDT Mon Jul 6 2015
...Flash Flood Watch through Wed Evening...
Issued a flash flood watch given the latest model guidance suggests
multiple rounds of showers/storms through Wed evening and we already
have very saturated grounds and a very moist airmass in place.
Mesoanalysis indicates an axis of 2+ inch precipitable water values
from the southern Plains into southern/central Indiana and points
northeastward ahead of a slow approaching sfc front. A few
different upper level shortwaves exist along this axis as well and
will continue to ride northeast producing multiple rounds of
showers/storms through Wed evening. H850 moisture transport is
strong and parallel running parallel to the boundary.
Because of these reasons and flash flooding in western KY/southern
MO/and southern IN this morning, believe that we will have several
more chances for flash flooding through Wed evening. The best
chances will come when convection strength peaks moving slowly ENE
or regenerating in the same areas leaving bands of intense rainfall
rates and amounts. Some areas this morning already received 2 to 4
inches of rainfall and expect that may be common with locally up to
5 by in these heavier rainfall bands that occur through Wed
evening. With 1 hr FFG running between 1.5 to 2.25 inches and 3 hr
FFG running between 1.9 to 3.9 inches, flash flooding will
certainly be possible.
The heaviest waves of precipitation look to be in a round of showers
and scattered storms this afternoon/evening and then another round
expected late tonight as the low level jet ramps up. Models are
having a difficult time with the individual waves, but feel this
might be the most reasonable soln with a general lull around
midnight and the early morning hours Wed. Also the early morning
round of showers and scattered storms should bring central KY the
heaviest rainfall as the sfc front sags further south closer to the
By late morning the frontal boundary will begin to lift north
shifting precip chances back northward. Also precip intensity will
weaken during the late morning/afternoon hrs Wed. For Wed night,
think that most of the area may see a dry period before a low
pressure system threatens the area toward sunrise.
Temps will be tricky depending on rainfall areas and exact frontal
boundary location tomorrow morning. With rain in the area in the
morning will stay on the warm side of guidance with lows in the mid
60s over southern IN to lower 70s over most of central KY. We
should see quite the range of high temps tomorrow again depending on
rain/cloud location and how quickly they move northward throughout
the day. Highs should be limited to the mid to upper 70s in rainy
areas with drier and partly cloudy locations reaching the low to mid
80s. Lows Wed night will be in the upper 60s/lower 70s.
.LONG TERM (Thursday through Tuesday)...
Issued at 250 PM EDT Tue Jul 7 2015
The long term will begin with quasi-zonal flow aloft. Ridging will
gradually build from the south as a southern ridge retrogrades. By
this weekend the forecast area will be on the periphery of this
upper level ridge.
For Thursday a weakening frontal boundary will slide in from the
north. This front will stall and continue to wash out across central
Kentucky Thursday. Scattered storms will develop near this boundary
on Thursday. These will mostly dissipate on Thursday night, but a few
showers or storms may hang around, so will not go completely dry
overnight. Friday continues to look wet in the models as a weak
upper level disturbance dive into the region. This combined with
residual boundaries from overnight convection to the north and
daytime heating will lead to renewed storm chances Friday afternoon.
Thus, have increased pops Friday afternoon.
Rain chances will decrease through the weekend as the ridge builds
in. Precipitation chances will somewhat depend on how strong this
ridge is. The best chance for any shower/storms over the weekend
will be across the northern Bluegrass and portions of southern
Indiana. Temperatures will be hotter through the weekend. Highs will
top out in the upper 80s to lower 90s with heat index values nearing
100 in the afternoons.
By Monday we will transition back to a more northwest flow pattern
with disturbances diving southeast through this flow. Thus, it looks
like we will see renewed rain chances early next week.
.AVIATION (18Z TAF Update)...
Issued at 145 PM EDT Tue Jul 7 2015
Multiple rounds of showers/storms are expected throughout the TAF
period as a slow moving front approaches the Ohio Valley. On and
off rounds of showers are most likely with scattered t-storms at
the peak of each round of convection. Have tried to highlight that
in the TAFs for the round of convection this afternoon/evening at
all TAF sites and then at BWG/LEX tomorrow morning with another
round of stronger cells. Flight restrictions will fall into the
LIFR/IFR cat in storms and will need to time these out with tempos
with each round. Have included an IFR tempo group for the
afternoon/evening round of storms. Low cigs and some light br may
become more common late tonight into tomorrow morning outside of any
convection. Steady rounds of convective activity should cease some
time tomorrow morning after sunrise as the boundary begins to lift
Winds will remain southwesterly through the TAF period. Some gusts
may reach 18-22 kts outside of t-storms this afternoon/evening.
Gusts higher than 25 kts will be possible in any t-storm.
KY...FLASH FLOOD WATCH through Wednesday evening FOR KYZ023>043-
IN...FLASH FLOOD WATCH through Wednesday evening FOR INZ076>079-083-