Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/21/19

Area Forecast Discussion

National Weather Service Louisville KY

 706 PM EDT Fri Sep 20 2019

...Updated Aviation Discussion...

.Short Term...(This evening through Saturday)
Updated at 323 PM EDT Fri Sep 20 2019

Convection from earlier this morning into the afternoon has
diminished for the most part. A few very light showers linger in our
Bluegrass region, but otherwise we are dry. The next focus for any
shower activity will be across southern Indiana toward sunset. The
HRRR has been consistent in showing some isolated development by 21-
22z in that area. The latest mesoanalysis data shows around 1500-
2000 J/KG of SB CAPE up in that area, however any convection will
likely be mitigated by a mid level inversion (~15000 Feet) evident
on forecast and AMDAR soundings. As a result, have only included
showers in the forecast and will leave thunder potential out. Some
of these showers could spill into the Louisville metro after sunset
so will mention a 20% pop along and north of I-64.

Any shower activity should diminish before Midnight, with dry
conditions persisting thereafter. Temps should drop back into the
60s for lows given modest radiational cooling conditions under
mostly clear skies.

Dry conditions will continue again tomorrow due to the upper ridge
and a notable subsidence inversion evident on forecast soundings. A
steady SW wind combined with 850mb temps around 16C should yield
highs in the upper 80s and low 90s. Decided to lean on high side of
guidance due to drought conditions and recent overachieving of
temps.

.Long Term...(Saturday night through Friday)
Updated at 250 PM EDT Fri Sep 20 2019

The persistent warm, dry ridge of high pressure aloft from the
southeastern U.S. into the lower OH Valley at the start of the
extended period will get shunted southward temporarily as a strong
shortwave trough moves across the upper MS Valley and Great Lakes
states on Sunday and Monday. This system will drive a cold front
southeast across the lower OH Valley and our area Sunday night and
Monday. Widespread showers and t-storms associated with the front
will occur well to our north and west on Sunday. However, as rain
spreads southeast toward the upper ridge, expect a weakening trend
in coverage and amounts over our area, where rain is much needed.
Showers will become more scattered in nature. Based on current model
solutions, expect rainfall amounts to vary from roughly around 0.25
inch in parts of southern IN to maybe around 0.1 inch south of the
OH River to only a couple/few hundredths of an inch in south-central
KY. Definitely no drought buster.

Surface high pressure will build into our area Monday night and
Tuesday with high temperatures closer to normal. Then, another broad
shortwave trough is forecast to move across the northern U.S. states
during the mid part of next week. This should drag another front
southeast across the OH Valley roughly Wednesday night or Thursday,
with only isolated to perhaps scattered showers possible in parts of
our area. Again, at this time, it looks like little or no help with
the drought.

However, this frontal boundary should not make it too far south as
the upper ridge begins to expand northward again. By the end of next
week, all models show this pesky ridge back in control over the
lower OH Valley and points southward, with a return to very warm to
potentially hot temperatures next weekend into the start of the
following week.

&&

.Aviation...(00Z TAF Issuance)
Updated at 705 PM EDT Fri Sep 20 2019

VFR conditions are expected this evening and during the overnight
hours. Winds will generally be light out of the south to southwest.
For Saturday, look for VFR conditions across the region with a
diurnal Cu deck around 5-6 Kft AGL.  Winds will be out of the
southwest at 8-10kts.

&&

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

$$

Short Term...BJS/CSS
Long Term....TWF
Aviation.....MJ