Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 292248
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
648 PM EDT Wed Jul 29 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Thursday Night)...
Issued at 335 PM EDT Wed Jul 29 2015
...Heat Advisory in Effect through this Evening...
Decided to issue a Heat Advisory for much of the area through 8pm
due to moisture/heat pooling ahead of an approaching cold front.
This spike in moisture/heat is occurring right at peak heating which
has caused heat index values to increase into the 105 to 110 degree
range. A line of storms should move into the heat advisory area
between 22-2Z providing relief from the heat.
Currently storms have fired along a left over boundary in the
Bluegrass region. These storms have very slow storm motions and a
tendency to train and back build so these may cause some flooding
issues. Storms were also developing along the cold front to our
northwest over IL/IN. These storms will persist and move SE
through our region late this afternoon/evening. Mesoanalysis
indicates plenty of CAPE/DCAPE/high precipitable water amounts in
the area which will be favorable for an isld damaging wind threat
and localized flooding threat. Some small hail is possible but
unlikely given a mid level cap in place which may limit storm
heights, very warm boundary layer temps, and a generally weak wind
profile. Storms should diminish or move south of much of the area
just after midnight. All areas should be dry on the back side of
the front by sunrise. Low temps tonight will range from the upper
60s to lower 70s.
Lower dewpts will bring much more pleasant humidity values to region
starting Thurs. Expect clearing skies for Thurs morning with a
mostly sunny afternoon and high temps in the mid to upper 80s.
Thurs night low temps should range through the 60s with some patchy
.LONG TERM (Friday through Wednesday)...
Issued at 310 PM EDT Wed Jul 29 2015
Flow regime at the beginning of the period will be characterized as
northwesterly flow aloft as ridging persists out across the western
CONUS and a corresponding trough hangs out along the eastern CONUS.
The flow is expected to amplify a bit over the weekend with both the
western ridge and eastern trough becoming larger, thus our flow will
be maintained out of the northwest. The latest data suggests
another weak frontal boundary will shift southward through the area
early in the weekend and then a series of surface high pressure
systems will progress across the region yielding sunny skies along
with less humid conditions.
Highs Friday and Saturday will be generally below average with low
to mid 80s being seen across much of the region. A few upper 80s
over the southern and southwest sections seems likely. We generally
stuck to the bias-corrected consensus all model blend here which has
had a good verification record over the past several days.
Dewpoints will remain in the low 60s through the period yielding
significant relief from the muggy conditions of late. There may be
a very isolated chance of a shower or storm on Saturday with the
front pushing through. However, convergence is not overall
impressive along the front, thus plan on keeping things dry at this
The relative quiet weather pattern from the weekend will likely come
to an end early next week as the northwest flow pattern is forecast
to become more active. The latest model data suggests that several
waves will drop down into the region within the northwest flow early
next week. At the same time, the overall amplitude of the western
ridge is forecast to decrease and become more flat. Thus, it
appears that the northwest flow pattern will become more progressive
as geopotential heights attempt to rise across southern Plains and
into the western portion of the southeastern US. In this type of
set up, it appears that an enhanced area of unsettled weather will
develop from the northern Plains through the Midwest and into
portions of the Ohio Valley. Overall, this pattern is not much
different than what we`ve seen of late, though the multi-model
consensus suggests that the main axis of convection and associated
rainfall may develop just north of our region.
Temporal timing of the waves in this pattern setup remain
problematic. Thus, it will be a few more days before things can be
really pinned down to a certain time frame. For now, plan on
keeping chance PoPs in the forecast Tuesday through Thursday.
Precipitation and expected cloud cover will likely keep temperatures
down below seasonal normals. Therefore, have gone with the cooler
side of the guidance envelope with temperatures. Highs will likely
top out in the low-mid 80s in the north with mid-upper 80s in the
.AVIATION (00Z TAF Update)...
Updated 645 PM EDT Wed Jul 29 2015
Finally got an organized line of storms to take advantage of all of
the heat across the region. That line has past KSDF, but cannot
rule out a cell popping up in the vicinity over the next couple of
hours. Whether that storm survives to KLEX given earlier storms
stabilizing the atmosphere is a little in question, but they could
see a wind gust around 2330Z, just before the new TAF valid period.
After these storms, we likely will see some vsby reductions
overnight until a cold front starts to dry us out on Thursday.
KY...HEAT ADVISORY until 8 PM EDT /7 PM CDT/ this evening FOR
IN...HEAT ADVISORY until 8 PM EDT /7 PM CDT/ this evening FOR