Severe Thunderstorm Warning 93, NWS Louisville, KY

Area Forecast Discussion
National Weather Service Louisville KY
630 AM EDT Sun May 7 2023

...Updated Aviation Discussion...

.Short Term...(Today and tonight)
Issued at 320 AM EDT Sun May 7 2023

Upper ridging continues to sit just east of the Mississippi River
Valley this morning, and we remain within a WAA regime thanks to a
50kt LLJ being observed on regional VAD Wind Profiles. In fact,
temperatures have only dropped to the upper 60s across the region so
far this morning.

We have been watching the organization of a MCS over west-central IL
this morning, which could bring some strong to marginally severe
storms to the forecast area later this morning. Despite CAMs
struggling in weakly forced environments, there has been good
consistency among hi-res guidance on placement and timing of this
morning's thunderstorm cluster, as seen on HREF ensemble paintball
composite reflectivity. As we are beginning to see this morning, the
cluster trajectory is shifting to the SE, riding along an
instability gradient that is expected to drive the cluster straight
into central KY. Low/mid level winds have veered to the southwest
already (per VAD Wind Profiles), which will aid in the advection of
a marginal to modestly unstable air mass over our region. Model
soundings have consistently suggested weak low level capping, but
this would easily be overcome by a developed cold pool and allow sfc
based convection to remain sustained through the late morning hours.
Relied on HRRR, WRF-ARW, and WRF-NSSL for timing of PoPs in the
morning forecast, which should be arriving in the I-64/I-71 corridor
by 12-13z, and continuing south and east through the rest of the
Commonwealth through the late morning. Damaging wind gusts will be
the primary hazard as this cluster punches into the region.

As the cluster pushes southward, subsidence in it's wake should
inhibit additional convection for at least several hours. Portions
of north-central KY and southern IN may end up dry for the rest of
the late morning and afternoon hours. However, confidence for this
afternoon and beyond is limited given the lack of a trigger in
place, and questions on if our atmosphere will destabilize again
after morning convection. This period is where CAMs begin to
diverge on solutions. There could be another cluster of
thunderstorms tracking into western KY by this afternoon, which
would have difficulty maintaining organization in our worked-over
environment. Did broad brush PoPs across the region for this evening
for potential for any interaction with sfc boundaries stemming from
upstream convection.

.Long Term...(Monday through Saturday)
Issued at 305 AM EDT Sun May 7 2023

HRRR/RAP, which have done well with daytime convection and this
morning's MCS to our northwest, advertise the possibility of
additional MCS development Sunday night over the Midwest on the nose
of a strong low level jet, heading southeast towards the middle or
lower Ohio Valley by Monday morning. The timing of any morning
thunderstorms will have an effect on the possibility of
redevelopment in the afternoon. With a moist, unstable atmosphere
remaining in place, the possibility of leftover convective
boundaries, uncertainties in timing, and the potential for
convection to our west during the day to move into the region, will
continue PoPs into Monday afternoon.

Monday night low pressure crossing Ohio will drag a cold front
through here in the pre-dawn hours on Tuesday. With dew points in
the low-mid 60s, moderate deep layer shear, steep mid-level lapse
rates, and broad CAPE profiles on sounding progs, will continue
likely shower & thunderstorm chances through Monday night ahead of
the front.

With the quicker fropa now being advertised, and after coordinating
with neighbors, have reduced PoPs for Tuesday. Didn't eliminate them
completely quite yet, but recent model trends are leaning more dry
than wet for the bulk of the day with north post-frontal winds
bringing in drier air as high pressure settles from Ontario into the
Great Lakes.

As that high drifts to the southeast we'll keep the forecast dry for
Wednesday and Wednesday night. Wednesday looks like a pretty nice
day with plenty of sunshine and afternoon highs in the upper 70s to
around 80 and dew points around 50.

Thursday through Saturday 5H riding builds overhead. However, return
flow between surface high pressure along the East Coast and low
pressure over the Plains will bring increasingly warm, moist,
unstable air into the region. Though the GEFS shows the main
moisture plume remaining to our west, it still looks like scattered
primarily diurnal thunderstorm activity may be possible, especially
by the time we get into Friday and Saturday.

Guidance shows daytime temperatures through the period around 5-10
degrees warmer than normal, which agrees with the CPC's 6-10
day temperature outlook.

&&

.Aviation...(12Z TAF Issuance)
Issued at 630 AM EDT Sun May 7 2023

Low confidence forecast for this morning as a cluster of
thunderstorms dives into our region from the north-northwest.
Updated timing of TEMPO groups to highlight when the most likely
timing for impacts will be expected. Ceilings will continue to lower
this morning to MVFR as showers and storms blanket the region, with
brief periods of lower vis also possible. Dry conditions are
expected for a short time in the wake of morning storms, but
confidence falls even more for this evening with shower/storm
potential. Highlighted terminals with broad PROB30 groups for now,
but will likely need alterations in future updates.

&&

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

Short Term...CJP
Long Term...13
Aviation...CJP

Hazardous Weather Outlook
National Weather Service Louisville KY
419 AM EDT Sun May 7 2023

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-080830-
Orange-Washington IN-Scott IN-Jefferson IN-Dubois-Crawford-Perry-
Harrison IN-Floyd-Clark IN-Hancock-Breckinridge-Meade-Ohio-Grayson-
Hardin-Bullitt-Jefferson KY-Oldham-Trimble-Henry-Shelby-Franklin-
Scott KY-Harrison KY-Spencer-Anderson-Woodford-Fayette-Bourbon-
Nicholas-Nelson-Washington KY-Mercer-Jessamine-Clark KY-Larue-Marion-
Boyle-Garrard-Madison-Butler-Edmonson-Hart-Green-Taylor-Casey-
Lincoln-Logan-Warren-Simpson-Allen-Barren-Monroe-Metcalfe-Adair-
Russell-Cumberland-Clinton-
Including the cities of Paoli, Salem, Scottsburg, Madison, Jasper,
English, Tell City, Corydon, New Albany, Jeffersonville, Lewisport,
Hawesville, Hardinsburg, Brandenburg, Hartford, Leitchfield,
Elizabethtown, Shepherdsville, Louisville, La Grange, Bedford,
Milton, New Castle, Shelbyville, Frankfort, Georgetown, Cynthiana,
Taylorsville, Lawrenceburg, Versailles, Lexington, Paris, Carlisle,
Bardstown, Springfield, Harrodsburg, Nicholasville, Winchester,
Hodgenville, Lebanon, Danville, Lancaster, Richmond, Morgantown,
Brownsville, Horse Cave, Greensburg, Campbellsville, Liberty,
Stanford, Russellville, Bowling Green, Franklin, Providence,
Scottsville, Glasgow, Tompkinsville, Edmonton, Columbia, Jamestown,
Burkesville, and Albany
419 AM EDT Sun May 7 2023 /319 AM CDT Sun May 7 2023/

This hazardous weather outlook is for portions of south central
Indiana and Central Kentucky.

.DAY ONE...Today and Tonight.

Thunderstorms will impact southern Indiana and central Kentucky through
the morning hours. Isolated severe storms are possible, with damaging
winds the main hazard.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

On and off thunderstorms will be possible both Monday and Tuesday. A
few storms could be strong to marginally severe, with heavy rain,
damaging winds, and frequent lightning being the main hazards.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time, but spotters should
remain abreast of the latest forecast updates.

GENERAL STORM MOTION OF THE DAY:

Storms will move from northwest to southeast around 30 to 35 mph.

Any users of this storm motion must be aware that thunderstorm
activity can be erratic and constantly evolving. Please use this with
caution and be prepared for changing conditions.

&&

More information, along with other weather, hydrological and
climate information can be found, at weather.gov/louisville.

CJP/13

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