Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 192304
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
704 PM EDT Sat Aug 19 2017

...Updated Aviation Discussion...

.Short Term (Now through Sunday Night)...
Issued at 100 PM EDT Sat Aug 19 2017

Fair weather is expected during the short term portion of the
forecast. This afternoon`s departing upper trough is forecast to
swing quickly up to the Northeast U.S. tonight. The parent Hudson
Bay low will get shoved east by an upstream trough/ridge pair over
Canada. Tonight through Sunday night, mid and upper level ridging
will steadily strengthen and expand over the Southeast U.S. This
will help confine the active storm track to the north of the
forecast area.

Temps will cool off into the mid/upper 60s early Sunday. With no
meaningful influx of drier air, dewpoints should also remain in the
mid/upper 60s tonight. Fog should become more common between 08-13z
Sunday and could be locally dense given mainly clear skies and light
winds. Sunday looks dry and mostly sunny, with highs around 90.
Areas west of I-65 are more likely to see highs in the lower 90s.

.Long Term (Monday through Saturday)...
Issued at 315 PM EDT Sat Aug 19 2017

Eclipse Day...

Surface and 850 mb ridging will slide a bit further east on Monday,
allowing a more uniform and light southerly return flow. However,
confidence continues to increase in a dry forecast. A shortwave
trough developing in the Plains, along with stronger moisture
transport, should fuel convection across parts of the Midwest, such
as Iowa and northern Missouri. RH cross-sections and forecast
soundings certainly show potential for thin cirrus on Monday. As for
the path of totality, will maintain a 20-30% sky cover forecast. For
eclipse viewing, the bigger concern would be diurnal cu development.
But the cu field shouldn`t be widespread. It actually looks more
widely scattered at best, and the resultant cooling during the
eclipse itself may actually diminish any cu floating around.

Monday does look hot, with high temperatures in the low 90s. Heat
Index values are forecast to reach the low/mid 90s just before the
eclipse and the mid/upper 90s immediately after the eclipse. Folks
planning to be outside for an extended period should dress for the
weather and drink plenty of water.

Tuesday-Saturday...

A strong upper trough will swing into the Great Lakes during the mid-
week period. A surface low is forecast to deepen as it moves
northeast into Quebec late Tuesday. This feature will drag a stout
cold front through the Ohio Valley Tuesday afternoon into Wednesday
morning. Showers and thunderstorms are likely to accompany the
front, and some strong to severe thunderstorms appear possible. The
main risk would be Tuesday afternoon and evening given the presence
of moderate instability and 30-40 kts of deep layer shear.

Tuesday is the last hot and humid day, with a substantial cool down
arriving behind the front for Wednesday. Highs Tuesday will range
through the mid 80s to around 90. Then, highs in the upper 70s and
low 80s are expected through the rest of the work week. Expect fair
weather with low humidity to persist into the weekend.

&&

.Aviation (00Z TAF Update)...
Issued at 655 PM EDT Sat Aug 19 2017

Isolated showers are on track to dissipate around sunset without
affecting any of the terminals, leaving fog potential as the main
challenge in this TAF set. Dewpoints managed to mix down into the
mid 60s this afternoon, so not as bullish on fog as in previous
forecasts. However, will still carry several hours of prevailing
MVFR visibility with TEMPO IFR conditions at both BWG and LEX on
Sunday morning. Could briefly go into LIFR at BWG, but not expecting
that to last.

By mid-morning all sites should recover to VFR, with light SW winds
and just a few fair-weather cu developing in the heat of the
afternoon.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Short Term........EBW
Long Term.........EBW
Aviation..........RAS


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