973
FXUS63 KLMK 090107
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
907 PM EDT Sun Sep 8 2024

.KEY MESSAGES...

* Fair weather this afternoon and Monday with one more chilly
  morning. Some filtered sunshine Monday with mid-level smoke from
  Canadian fires dropping southeast into our area.

* Overnight lows tonight will dip into the 40s. Temperatures in the
  low to mid 40s could approach or break low temperature records at
  Lexington and Frankfort.

* Dry weather is expected through Wednesday night.  A tropical
  system is expected to bring showers to the region Thursday night
  through much of next weekend.  Forecast confidence on rainfall
  amounts remains below average at this time.

&&

.UPDATE...
Issued at 907 PM EDT Sun Sep 8 2024

Hazy skies will continue through the overnight hours as some smoke
from Central Canada drifts over the region. Most of the mesonet
sites have already dipped into the upper 50s, therefore, have
lowered Min Ts over the region by about a degree. Models are still
showing quite a bit of uncertainty with Min Ts for Monday morning.
It is unclear how much the upper level smoke will prohibit cooling.
However, still have a good shot at seeing temperatures similar to
the previous morning in the low 40s and a decent shot at breaking or
getting close to record low temperatures. Have added some thin,
patchy fog in the river valleys given persistence, light winds, and
mostly clear skies. Otherwise, the current forecast remains on track
with high pressure and pleasant fall conditions.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 250 PM EDT Sun Sep 8 2024

Very dry airmass in place for this time of the year, with 12Z
Nashville sounding showing a precipitable water of 0.46", very close
to the min for this date. Unfortunately the brilliant blue skies of
yesterday appear to have taken on a hazy form, with latest Smoke
HRRR model showing some smoke aloft dropping down from central
Canada. GOES Natural Color imagery is showing this haze, being a
littler thicker now over central IL/IN/OH, and that area is headed
southward. Expect the hazy skies to continue this period.

Otherwise, no concerns in this forecast cycle. Surface high pressure
centered just to our northwest will wobble to a position over the
mid Ohio Valley by tomorrow afternoon, bring very light and variable
winds. Expect another cool night. Temperature comparisions from this
morning to tomorrow will depend on how the balance between calm
conditions works with that smoky layer aloft. For this package, will
lean towards it being 1-3 degrees warmer for most locations, with
coldest spots likely in the low-mid 40s. Highs tomorrow under that
filtered sunshine should be several degrees warmer than today, as
low-level thicknesses quickly increase. Should be in the low to mid
80s for most.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 250 PM EDT Sun Sep 8 2024

Monday Night through Wednesday Night...

Upper troughing over the Ohio Valley currently is forecast to lift
well off to the northeast by Monday night with heights building
across the area in its wake.  The flow pattern is forecast to remain
unremarkable with dry and tranquil weather expected through the
period.  Lows Monday night will generally be in the very low 50s
across much of the area.  A few of our deeper valley locations
probably will drop into the mid-upper 40s.  Temps will rebound
rather quickly on Tuesday with highs in the mid-upper 80s and lows
Tuesday night in the low-mid 50s.  As heights continue to build on
Wednesday, we should see most locations get into upper 80s to around
90 for highs.  Lows Wednesday night look to drop back into the upper
50s and lower 60s.

Thursday through Sunday...

By mid-week, large scale hemispheric pattern will find mainly zonal
flow over the northern CONUS.  A well advertised tropical cyclone
should be in progress in the northwest Gulf.  This cyclone, may make
a landfall somewhere in the LA area late Wednesday/early Thursday.
The multi-model consensus continues to tighten up here with all
three (GFS/CMC/Euro) tracking the system northward along the MS
River and having it located in NE AR by Friday morning.  Given the
multi-model consensus, it appears this system will bring much needed
rainfall to the region beginning as early as Thursday afternoon and
continuing through the weekend as the system may end up stalling out
across portions of the TN/OH Valleys.

QPF amounts from the models still contain substantial uncertainty
and contain a large amount of spread.  The Canadian is the wettest
of the bunch suggesting several inches of rain being possible.  The
GFS and Euro are not as robust as the Canadian, but offer some
helpful QPF for our drought areas. Overall, forecaster confidence is
a bit higher than 12 hours ago with regards to seeing some QPF, but
confidence in amounts (at days 5-7) remains below normal.

Highs on Thursday should feature a gradient with warmer temps up
across southern IN and northern KY where lesser amounts of cloud
cover will be found.  Highs in the upper 80s look likely here, but
mid 80s will be likely over southern KY.  Highs Friday and Saturday
will be quite cooler with expected cloud cover and precipitation
around.  Will go with upper 70s to the very low 80s for highs here.
Temps probably will not change too much for Sunday with highs
staying in the upper 70s to the very low 80s.

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 716 PM EDT Sun Sep 8 2024

VFR weather expected. Sfc high pressure currently centered over
western IL will drift ESE over the Lower OH Valley tonight. Expect
clear skies and light and variable tonight and Monday.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

UPDATE...SRM
SHORT TERM...RJS
LONG TERM...MJ
AVIATION...SRM