Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 181105
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
705 AM EDT THU AUG 18 2016

...Updated Aviation Discussion...

.SHORT TERM (Now through Friday)...
Issued at 300 AM EDT Thu Aug 18 2016

Current satellite imagery and observations reveal partly to mostly
cloudy skies across the forecast area this morning.  Area radars
still show some light rain showers down across southern KY...mainly
south of the Cumberland Parkway near the stalled out frontal
boundary.  Further north, some partial clearing has occurred and
with dewpoint depressions fairly low, areas of fog have developed.
Early morning temperatures were in the lower 70s.

In the near term, we expect the rain showers to continue across the
far southern parts of the forecast area through sunrise.  Further
north, we expect skies to remain partially clear with areas of fog
continuing.  Some of the fog may be locally dense in some spots.
Will continue to monitor conditions and if conditions deteriorate
further, a Dense Fog Advisory may be required.

For today and tonight, stalled out frontal boundary looks to remain
checked up near the KY/TN border.  Latest CAMs suggest that
scattered storms will be most numerous over the southern sections of
the forecast area with 40-50% coverage.  Some isolated storms as far
north as the Parkways still look possible as well.  Convection will
be diurnally driven, so expect coverage to drop off around sunset
with the loss of heating.  Temperatures will be a challenge as
clouds and precipitation will be around today.  We stuck close the
the CONSShort blend which has done well in the past few days.  This
would result in temperatures warming into the lower 80s in areas
north of the BG/WK Parkways with upper 70s to around 80 in areas
south of the Parkways.  Lows tonight should cool into the upper 60s
to the lower 70s region wide.  Another wave looks to move in late
tonight which may result in additional convection moving back into
southern KY late tonight.

Friday will feature another day of more diurnally driven showers and
storms. The best coverage will likely be across the southern
sections once again given their closer proximity to the stalled out
frontal boundary.  Convective coverage may be slightly more Friday
afternoon further north, but for now plan on keeping things in the
low chance range at this time.  Highs Friday look to warm into the
lower 80s.

.LONG TERM (Friday Night through Wednesday)...
Issued at 335 AM EDT Thu Aug 18 2016

...Strong Storms Possible Late Saturday and Early Sunday Followed By
Much Cooler Conditions Next Week...

====================================
Synoptic Overview
====================================

Amplifying upper level pattern will be in full swing at the
beginning of the period as a strong upper trough axis pushes through
the northern Plains.  The upper trough and associated surface
cold front will shift through the Ohio Valley on Sunday with a round
of strong convection preceding it.  In the wake of the frontal
boundary, much cooler and drier air will push into the region.
Temperature departures of 12-15 degrees are expected which will make
conditions feel more like mid-late October than late August.  Dry
conditions are expected through about midweek before another trough
axis approaches the region from the west late in the period bring
the next round of precipitation to the region.

====================================
Model Trends/Preference/Confidence
====================================

Overall model solutions are in fairly good agreement through the
period.  Temporal and spatial differences between the deterministic
runs and the ensemble members from the various models continue to
tighten up a bit...leading to increased forecast confidence.  There
is still a bit of spread regarding temperatures in the post frontal
airmass for Monday and Tuesday, but the spread is smaller than in
previous runs.  Overall, have trended the forecast to a blend of the
previous forecast while incorporating the trends from the latest
Euro and OP GFS runs.  Overall forecast confidence remains slightly
above average through the long term period.

====================================
Sensible Weather Impacts/Threats
====================================

Precipitation chances will ramp up Saturday afternoon and evening as
the cold front approaches from the northwest.  Strong convection may
pose a risk across the region.  However, the strength of convection
will largely be determined by how much instability will be available
as the front comes through the region.  The threat actually looks a
little less than in previous forecasts.  This is because the front
looks to outrun the better upper level forcing and bulk shear. These
two ingredients will be more focused across the Great Lakes states
and lag behind the actual front.  Nonetheless, unsettled weather is
likely from late Saturday through early Sunday.  Sunday will be the
main transition day across our region as the muggy conditions will
hold on through much of the day before the drier air starts to
advect in late in the day.

We should see clearing take place Sunday night with drier and much
cooler conditions moving into the region for Monday-Tuesday.  Highs
Monday and Tuesday will top out in the upper 70s to the very low 80s
with overnight readings falling into the mid-upper 50s.  Some lower
50s will be possible Tuesday morning in the more sheltered
locations.

Dry weather will continue with a moderation in temperatures as we
head toward midweek. The latest guidance suggests that mid-level
heights will continue to rise across the region as the next mid-
level trough axis swings across the Plains.  This feature may start
to affect our weather around Wednesday with a threat of showers and
storms late in the period. Highs Wednesday should warm back into the
mid 80s region wide.

&&

.AVIATION (12Z TAF Update)...
Issued at 655 AM EDT Thu Aug 18 2016

A stream of low and mid-level moisture continues this morning from
central TX northeastward across TN and southern KY. Scattered
showers are noted over parts of south-central KY at this time, and
these could affect BWG periodically for next few hours.

Cigs and vsbys have been variable overnight. Overall, low clouds
have hung in or developed as expected with cloud base heights at or
below 1000 ft. However, these cigs are beginning to rise to high end
IFR or MVFR, and this trend will continue until clouds become VFR
later this morning or early afternoon at SDF and LEX. So far, BWG
has been void of many low clouds. Vsbys also have come up at LEX,
and these too should remain VFR, although cannot preclude brief
lower vsbys thru 14z this morning.

Cig and vsby conditions may deteriorate tonight again as model
soundings and cross-sections show redevelopment of at least MVFR and
quite possibly IFR clouds. Vsbys should drop to MVFR at least.
Scattered showers may again affect BWG, with isolated showers
possible near SDF or LEX, but not numerous enough to include in
their TAFs at this time.

&&

.LMK Watches/Warnings/Advisories...
KY...NONE.
IN...NONE.
&&

$$

Short Term........MJ
Long Term.........MJ
Aviation..........TWF



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