Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 261335
Area Forecast Discussion
National Weather Service Louisville KY
935 AM EDT TUE JUL 26 2016
Issued at 935 AM EDT Tue Jul 26 2016
Never thought we would be calling dewpoints in the lower 70s "less
humid" but a slightly less humid air mass is in place over at least
southern Indiana and north-central Kentucky this morning. A weak
boundary from near Bloomington to near Cincinnati is already fairly
active, but appears to be lifting ever so slowly to the north. Still
expect convective temps to be reached before noon, which will help
other boundaries light up across Kentucky. Overall forecast for the
day remains on track, but will do a quick update to massage the
hourly trends, including a slightly slower expansion of precip
.SHORT TERM (Now through Wednesday)...
Issued at 300 AM EDT Tue Jul 26 2016
In the near term, partly cloudy skies were noted across the forecast
area. Temperatures were a bit cooler than in the past few overnight
periods with most locations currently in the lower 70s. For the
remainder of the overnight period, we expect partly cloudy skies to
continue with some patchy fog developing in areas that clear out and
get in a bit more radiational cooling.
As for today`s forecast, we expect another repeat performance from
Monday. The day looks to start off dry, but morning heating will
allow us to reach convective temperatures pretty quick. High res
CAMs suggest that storms will break out across southern Indiana by
late morning and then push southward into Kentucky during the
afternoon. So we plan to ramp PoPs up in the late morning and
peaking in the late afternoon hours. Mid-level flow is rather weak
and wind shear is not all that great. Model proximity soundings
show a moisture rich environment across the region this afternoon.
Storms that develop will be capable of producing torrential rainfall
and gusty winds as precipitation loading of storms may lead to an
increased wet microburst potential. With the storms capable of
producing torrential rainfall, some localized flooding issues could
crop up during the afternoon hours. High temperatures should top
out in the upper 80s in the north with upper 80s to the lower 90s in
the south before storms develop.
Convective coverage looks to diminish once again with the loss of
heating tonight. Skies may partially clear out overnight resulting
in patchy fog development once again. Lows look to cool into the
lower 70s. A similar weather pattern is expected to continue into
Wednesday with diurnally driven convection expected during the
afternoon and evening hours. Heavy rainfall will be possible again
with storms Wednesday. Highs look to top out in the upper 80s to
.LONG TERM (Wednesday Night through Monday)...
Issued at 317 AM EDT Tue Jul 26 2016
...HEAVY RAINFALL LIKELY WEDNESDAY NIGHT THROUGH FRIDAY NIGHT...
The latest round of guidance continues to be in good agreement with
the upper level pattern undergoing amplification through the period.
In general, the large upper ridge that has been responsible for the
recent warmth is forecast to break down. As this occurs, a
significant mid-level wave will move from the inter-mountain west
and amplify as it swings through the Ohio Valley. The upper trough
will expand and stall out over the eastern US while ridging
continues to strengthen across the western states. This pattern
will lead to very unsettled weather across the Ohio Valley through
the first half of the long term period (Wed night through Friday
At the surface, a stalled out frontal boundary will remain draped
across the region. A broad southwesterly flow will continue to pump
copious amounts of rich low-level moisture into the region.
Precipitable water values will remain well above seasonal normals
through the period with values at or above 2 inches. Diurnally
driven instability aided by the upper trough moving through will
set the stage for widespread convection to develop. The convection
will be most widespread from Wednesday night through Friday. While
it will not likely rain the entire time, several rounds of showers
and thunderstorms will likely move through the area. Organized
severe weather risk looks to remain low through the period with the
main threat being heavy rainfall. Several inches of rainfall will
be possible through the period. This rainfall combined with
rainfall expected earlier in the week may result in more widespread
hydrologic issues by the time we get to the weekend as areas may see
repeated/training rainfall. Should future forecasts continue to
advertise the heavy rain threat, a Flash Flood Watch may need to be
considered for future forecasts.
As we head into the weekend, there has been an increasing signal in
the data for the trough to deepen and head off more to the east.
This would effectively push the stalled out frontal boundary to our
south and bring some relief to the region from the wet/unsettled
weather pattern...especially to our northern areas. For now, have
trended the forecast a little drier in the north for the weekend,
but with the boundary in close proximity to our southern areas,
isolated-scattered showers/storms may continue into early next week.
A look ahead suggests that ridging may build back into the region by
early next week. That kind of pattern transition would result in
drier weather, but not an overall hot pattern by any means.
Temperatures through the early part of the period will likely run
slightly below normal due to expected shower and thunderstorm
activity. Highs Thursday may only warm into the lower-mid 80s with
overnight lows in the lower 70s. Temps Fri-Mon look to top out in
the upper 80s with overnight lows remaining in the low 70s.
.AVIATION (12Z TAF Update)...
Issued at 634 AM EDT Tue Jul 26 2016
Main TAF concerns will be fog this morning and convection potential
this afternoon. Fog is worst at Lexington where LIFR vsbys have
prevailed for the past couple of hours, a trend which should
continue for another hour or so before conditions rapidly improve.
Otherwise, the fog at LEX and perhaps some light BR at BWG will
quickly burn off this morning. Latest guidance continues to focus
convection nearest to the front this afternoon which will be in
closest proximity to LEX/SDF. Therefore, will introduce TEMPO groups
there for convection this afternoon. While a few storms will be
possible around BWG as well, looks as if there could be a bit better
capping there today so will limit them to just VCTS for now. Outside
of storms, today will feature diurnally-driven cumulus and passing
mid/high clouds with light WSW winds. Additional fog development
will be possible tonight if the sites receive rainfall today, but
will leave any mention out for now until those trends can be better
identified through the afternoon hours.