Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 271105
Area Forecast Discussion
National Weather Service Louisville KY
705 AM EDT Mon Mar 27 2017
Issued at 700 AM EDT Mon Mar 27 2017
Warm advection band of showers and thunderstorms currently lifting
quickly northeast into western KY oriented NW to SE. This activity
is on the nose of the 850 mb LLJ/strongest moisture transport.
Nudged precip/thunder arrival an hour or two earlier in the grids to
account for faster motion.
These showers and storms will likely push into the western CWA
around 12-13z. Severe weather is not likely with morning convection,
but brief heavy rainfall, gusty winds, and lightning are possible.
.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-
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
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 (12Z TAF Update)...
Issued at 645 AM EDT Mon Mar 27 2017
Extensive mid-level cloud shield spreading across western Kentucky
into central Kentucky, but with calm winds there remains a narrow
window for reduced visibilities early this morning. BWG was briefly
restricted earlier but recovered quickly, and may be able to
initialize VFR if there is enough of a mid-level ceiling.
Warm advection wing setting up over western Tennessee will lift
northward and could spark showers by midday in the terminals. BWG
will be the first to be impacted, while it may take until mid-
afternoon for LEX. Will carry VCSH, but more confidence in a strato-
cu ceiling which should stay VFR.
A fairly solid band of showers and thunderstorms should swing
through during the evening, but still limited confidence in any
impacts to ceilings. Have kept ceilings VFR, if only just barely,
but will go prevailing MVFR on visibilities. Could see brief drops
into IFR accompanied by gusty winds, but timing remains too
uncertain to be more pessimistic than VCTS/CB.
Precip clears out after midnight tonight, but plenty of low-level
moisture hangs around and the gradient gets sloppy in the vicinity
of a trailing sfc trof. Strato-cu should keep vis from tanking
completely, but will go with some light fog and MVFR visibilities
toward Tue morning.