Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 270845

Area Forecast Discussion
National Weather Service Louisville KY
445 AM EDT Mon Mar 27 2017

...Updated Long Term Discussion...

.Short Term (Now through Tuesday)...
Issued at 245 AM EDT Mon Mar 27 2017

...Strong to Severe Storms Possible This Afternoon and Evening...

Today`s mid-level feature of interest can be seen spinning in
eastern Kansas on WV imagery early this morning. This progressive
wave is forecast to eject due east across the OH Valley today into
tonight. Meanwhile, in the low levels, a surface low was analyzed
over eastern Oklahoma early this morning, with a subtle surface
boundary extending eastward into the TN Valley. Over NW Arkansas by
12z, the surface low is forecast to move northeast to southern IN by
late tonight. As this occurs, moisture return gradually ramps up in
the warm sector of the system. Surface dewpoints are forecast to
rise into the mid to upper 50s,  with 60 dewpoints possible in the
SW forecast area.

The atmosphere begins to destabilize by mid to late morning. Most
areas will stay dry through 15z. Latest hi-res models do suggest
isolated to scattered warm advection showers/storms moving into the
forecast area after 14-15z. Plenty of cloud cover throughout the day
will also help to suppress surface heating a bit. The latest RAP/GFS
soundings suggest MLCAPE values in the 500-1000 J/kg range, with the
higher values further to the south and west. This aligns well with
SPC`s Day 1 Outlook, which features a Slight Risk for central
KY/southern IN and an Enhanced Risk across western KY/TN.

Deep layer shear is also sufficient for sustaining organized
convection, with 0-6 km values of 35-40 kts. Most likely storm modes
are multicells and linear segments. Some bowing linear segments will
be possible, and the main severe hazard is damaging winds. However,
given the proximity of the surface low as it tracks roughly along
the Ohio River this evening, there is some potential for an isolated
tornado or two to spin up. RAP soundings show some backing of the
surface flow this evening, with effective SRH maxing out near 200-
250 m2/s2.

As far as timing, severe weather looks possible mainly from 5 pm -
midnight EDT. Low pressure moves east of the area by 12z Tue, and
some showers could linger into Tuesday morning east of I-65. Highs
will reach the low to mid 70s this afternoon, with lows in the mid
to upper 50s tonight. Tuesday will be cooler, but still a bit warmer
than normal, with highs in the mid 60s to around 70 degrees.

.Long Term...(Tuesday night through Sunday)
Issued at 415 AM EDT Sun Mar 26 2017

The middle portion of the week will feature quiet weather, with a
dry forecast Tuesday evening through Wednesday evening. This is our
next brief window of upper level ridging before the next low
pressure system cycles through in this active flow pattern. Highs in
the mid 60s to low 70s Wednesday will warm into upper 60s to mid 70s
for Thursday.

Rain chances ramp up on Thursday as a deep upper trough approaches
the region, maxing out Thursday night into Friday morning. There is
at least a slight chance for storms during this period as well.
Decent agreement between 27.00z GFS/ECMWF on the cold front clearing
the forecast area Friday afternoon. Highs on Friday should be in the
mid to upper 60s, with cooler air filtering in behind the front.
Lows will drop into the 40s Saturday morning. Saturday is the
coolest day over the next week, with highs in the low to mid 60s.
Timing the next potential for precip is quite uncertain, but looks
to arrive by late Sunday or Monday. Sunday could end up dry, with
highs in the mid to upper 60s.


.Aviation (06Z TAF Update)...
Issued at 1255 AM EDT Mon Mar 27 2017

Shortwave ridging in between two upper impulses has quieted down the
weather across Kentucky, with VFR conditions and light winds. Will
carry a few hrs of MVFR visibilities in BWG just either side of
daybreak, as the fog climo there still seems to trump the potential
mid-level ceiling. Otherwise moderate to high confidence that
conditions will remain VFR through at least mid-afternoon on Monday.

Strato-cu deck comes in late morning in response to warm
advection/weak isentropic lift. However, looks like it stays just
barely VFR, if it is actually enough for a ceiling. Will carry VCSH
during this time period as well, with the best shot initially at
BWG, then trending toward SDF and possibly LEX later in the

A more solid band of showers and storms comes in during the evening,
and will warrant prevailing SHRA, with just VCTS/CB. Fairly
confident in MVFR prevailing visibilities, but can`t rule out brief
IFR periods in the stronger cells. Less confident in the ceiling, as
none of the model guidance is hitting any restrictions hard at all
and we haven`t seen ceilings go down and stay down the last couple
days. Will keep ceilings VFR.




Short Term........EBW
Long Term.........EBW
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