Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 231405
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1005 AM EDT Thu Mar 23 2017

.Forecast Update...
Issued at 1002 AM EDT Thu Mar 23 2017

The forecast was updated to allow the Freeze Warning to expire. No
other major changes made.

Issued at 908 AM EDT Thu Mar 23 2017

Rain with embedded thunderstorms continues to push eastward this
morning. The latest mesoscale models do show it weakening and
dissipating by early afternoon, but it does look like some showers
could affect mainly south central KY. Have added in a slight chance
of rain and thunderstorms to the forecast to account for this.

&&

.Short Term (Now through Friday)...
Issued at 253 AM EDT Thu Mar 23 2017

Current surface analysis reveals our region being influenced by a
1035mb high pressure over Michigan. Surface winds have been
generally light out of the northeast at this hour. GOES-16 reveals
mainly clear skies and only some patchy mid to high level clouds
over central KY. The combination of dry air, light winds and mostly
clear skies have allowed temperatures to drop into the 30s across
the CWA, and at or below the freezing mark across much of
northeastern KY. Should see temperatures continue to fall through
sunrise and think current freeze warning in place is holding up well.

After a cold morning, the rest of today is looking to be mild and
dry. Strong surface high pressure will be in place over southern New
England, while cyclogenesis will be ongoing across the central
Plains. This type of setup will result strong warm air/moisture
advection within a broad southerly flow regime across the Plains and
eventually the Tennessee/Ohio River Valleys as the system propagates
eastward. As mentioned earlier, not expecting any rain today, but
high to mid level clouds will increase through the day as warm front
lifts north of the CWA, and should see near overcast skies by late
afternoon.

LLJ develops overnight ahead of the strong storm system in the
central Plains. Might see a few sprinkles or very light showers as a
weak shortwave passes near the CWA, but think chances are too slim
to include in the grids so have kept forecast dry for the overnight
hours.

By Friday, the low pressure system that formed off the Rockies from
the previous day will begin to weaken over the KS/OK border as the
system becomes stacked. The CWA will still be well within the warm
sector of the system, and despite widespread clouds, should see
temperatures quite warm, with highs generally in the low 70s thanks
to strong WAA. Similar to Thursday night, might see a few isolated
sprinkles or very light showers in the morning, but not enough to
warrant including in the grids at this time.

.Long Term (Friday Night through Wednesday)...
Issued at 304 AM EDT Thu Mar 22 2017

A rather active and unsettled pattern remains in place for the long
term period, with multiple waves bringing potentially widespread
precipitation.

Friday night - Sunday...

The low pressure system that was over KS/OK Friday morning will lift
northeastward toward our CWA for the weekend. A rather broad line of
showers and embedded thunderstorms will approach western portions of
the CWA Saturday morning before spreading eastward during the
afternoon. While there are some minor differences in NWP guidance
with precipitation coverage, they generally agree that the showers
and thunderstorms will weaken as they move eastward. Some models
even show eastern parts of the CWA remaining completely dry during
the day Saturday.

A second line of precipitation east of an ULL in MO will develop
Saturday afternoon and move across the CWA Saturday night through
Sunday morning. This line looks like it`ll hold together much better
than the first line. Most models show a weak tongue of instability
(MUCAPE < 500J/Kg) associated with this line of precipitation, so
some embedded thunderstorms within the rain showers will certainly
be possible. All of that should push east of the CWA by late Sunday
morning.

Depending on the track of the ULL, might see some wrap around
moisture and showers Sunday afternoon. Should see all precipitation
end by Sunday evening.

Monday - Tuesday night...

Another strong shortwave trough is progged to impact the area Monday
afternoon. A bit too early to get into any sort of detail with this
setup, but this shortwave trough will bring another round of showers
and thunderstorms to the region, starting Monday and continuing
through most of the day Tuesday.

Beyond Wednesday...

Long range models vary on upper level pattern as well as the track
and strength of a cold frontal passage Tuesday afternoon. The GFS
pushes a cold front almost down to the Gulf of Mexico and is some 15-
25F degrees colder than the ECMWF for highs Wednesday and Thursday
afternoon. For now, will keep a blended forecast, but it appears
that the pattern will still be active and favorable for more
precipitation through late next week.

&&

.Aviation (12Z TAF Update)...
Issued at 640 AM EDT Thu Mar 23 2017

Will maintain VFR, but with thickening and lowering cloud cover as
the departing surface high gives way to southerly return flow. Mid-
level ceiling comes in late in the day, but now looking like a
better chance for a strato-cu ceiling developing around the same
time, but just barely remaining VFR.

Low-level jetting really cranks up this evening, with 2000 foot
winds pushing 40 kt. Forecast soundings also show a strong inversion
developing, which will help focus speed shear. Will hold off one
more cycle before including LLWS in the TAFs, as shear would be
mitigated if the inversion is even slightly above 2000 feet.


&&

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

$$

Update...EER
Short Term........DM
Long Term.........DM
Aviation..........RAS


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