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Area forecast discussion 
National Weather Service Louisville Kentucky
105 am EDT Thu Aug 21 2014

..updated aviation discussion...

Short term (now through sunday)...
issued at 300 PM EDT Wed Aug 20 2014

Temperatures in the mid 80s to around 90 with dewpoints in the
low-mid 70s is making for an uncomfortable afternoon, with a few
storms starting to pop up. Deck of high clouds streaming in from the
northwest has helped to hold off significant development across most
of our region to this point. Have a thunderstorm complex developing
in the unstable airmass over north central TN, and this complex may
force some new storms to develop along an outflow boundary in
southern Kentucky. A few storms also are forming along the corridor from
Hancock County to Casey County in KY, with even more storms east of
the complex over south central in.

Best instability and moisture still resides over southern KY, so
will keep most focus for severe weather down there the next few
hours, with a secondary focus over our southeastern counties. For
this evening, should continue to see scattered development away from
these focus areas, with the northeast forecast area having the best
chance to continue with storms after midnight. This region will
continue to be the focus for development the next few periods, as a
ridge aloft should help dry out our southwest forecast area Thursday
and Thursday night.

That ridge will provide hotter temperatures in our southwest as
well, with highs Thursday likely reaching the mid 90s. Heat indices
could top out around 100. Given potential for some cloud cover have
not gone into the next category, 100-105, for heat indices there.
Think we can hold off on our more prolonged period of near heat
advisory criteria until Friday, read on in the discussion below.

Long term (sunday night through friday)...
issued at 306 PM EDT Wed Aug 20 2014

Friday - Monday...

..heat, humidity, and generally unsettled weather this weekend...

An upper ridge will be in place through this weekend and into next
week, keeping hot and muggy conditions in place. Upper ridge looks
"dirty" with very little in the way of a subsidence inversion
normally seen with this type of environment. Therefore, can't do
away with storm chances each afternoon and evening. Models are
generally all over the place with expected precipitation fields each
day, despite the fairly good agreement in the overall pattern.
Therefore will just keep isolated to scattered thunderstorms in the
forecast pretty much every day and evening.

As far as temperatures go, highs look to top out in the low and mid
90s each day Friday through Monday as a core of 850 mb temps between
20 to 23c settle over the area. Some spots could touch the upper 90s
in our western Kentucky counties. Heat indices will be a bit of a
concern during this time period as the hot temperatures will combine
with dew points in the low and even mid 70s. Highest heat indices
each afternoon could top out in the 100-105 range, so forecast needs
to be monitored for a potential heat advisory due to a prolonged
period of days where heat indices approach criteria (105f). This
advisory would come with a later forecast issuance. One factor that
could limit temperatures and associated heat indices could be the
afternoon/evening convection.

Tuesday - Wednesday...

Confidence lowers for the Tuesday/Wednesday time frame as some
degree of troughing over the western Continental U.S. Tries push the upper
ridge axis east. Should this scenario play out, it would bring
better chances for storms to our western cwa, along with
temperatures not as hot. As a result, will go with highs around 90.


Aviation (00z taf update)...
issued at 110 am EDT Thu Aug 21 2014

Warm humid weather with light southwest winds will continue today
and tonight. South southwest winds around 5 to 7kt this morning will
become southwesterly around 7 to 9kt this afternoon, before becoming
light southerly this evening through early Friday morning.

Bwg had heavy rain earlier Wednesday afternoon and this may lead to
some fog during the pre-dawn hours. Currently, light southerly winds
has kept fog at Bay. Think that is is more likely than not the
visibilities will only lower into the MVFR range at bwg this morning
if fog develops at all.

VFR flying conditions are anticipated outside of any scattered
thunderstorms that may affect sdf or Lex as early as the mid-morning
hours today. Coverage of any convection will be scattered and
disorganized and difficult to time. Due to only scattered pops, will
keep thunder out of the tafs at this point.


Lmk watches/warnings/advisories...


Short term........rjs
long term.........Bjs

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