472 
FXUS63 KLMK 310708
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
308 AM EDT Tue May 31 2022

.Short Term...(Today and tonight)
Issued at 305 AM EDT Tue May 31 2022

Another dry and very warm day is in store as high pressure at the 
sfc and aloft remains parked over the southern Appalachians. Progged 
low-level thicknesses and H9/H8 temps suggest that we'll end up 
close to persistence for highs this afternoon, perhaps a degree 
warmer. Will trend tonight's lows up a degree or two from this 
morning to account for a little better mixing as a cold front slowly 
approaches from the NW.

&&

.Long Term...(Wednesday through Monday)
Issued at 250 AM EDT Tue May 31 2022

Wednesday through Thursday night...

Mid- and upper-level ridging across the eastern CONUS is expected to 
break down as we head into Wednesday and the latter half of the 
week. A series of shortwave disturbances/vorticity lobes will swing 
along the southern periphery of a large upper low located near 
Hudson Bay, gradually but consistently shifting the mid- and upper-
flow regime from ridging to troughing by Thursday night/Friday 
morning. The most highly-amplified shortwave will have an attendant 
surface cold front which is expected to extend SW-NE from the 
southern Plains, across IL/IN, and into southern ON Wednesday 
morning. Global model guidance is generally in good agreement with 
the evolution of the front, taking it slowly southeastward during 
the day on Wednesday, bringing it to near the Ohio River overnight 
Wednesday night before pushing it through central Kentucky during 
the day on Thursday. At present, the progression of the cold front 
is expected to be slow enough for all areas across southern Indiana 
and central Kentucky to once again surge into the mid-to-upper 80s 
to near 90 Wednesday afternoon. 

Current global and mesoscale model depictions suggest that the cold 
front should serve as the main initiating boundary for convection 
Wednesday afternoon through Thursday night. Forecast soundings 
contain more than sufficient instability in the pre-frontal 
environment Wednesday afternoon (MLCAPE 2000-3000 J/kg); however, 
vertical wind shear will be lackluster thanks in part to only 15-20 
kt flow at both 850 and 700 mb. With forecast soundings also showing 
considerable low- and mid-level dry air, the potential exists for 
quite negatively-buoyant downdrafts in strong storms, which could 
create some damaging wind concerns Wednesday afternoon and evening. 
Unsurprisingly (given antecedent ridging), melting heights will be 
quite height Wednesday afternoon, and low/mid-level lapse rates will 
generally be in the 6.5-7 deg C/km range, so the environment is not 
particularly favorable for large hail. However, given the amount of 
instability, isolated severe hail cannot be ruled out in storms with 
the strongest updrafts.

There should be a nocturnal lull in convection Wednesday night into 
Thursday morning as the near-surface layer stabilizes and overall 
instability decreases. However, with the front close by and 
increasing low- and mid-level moisture, expect shower chances (with 
a few embedded thunderstorms possible) to persist overnight 
Wednesday night. Lows Thursday morning will be mild, only falling 
into the mid-to-upper 60s. Another chance for scattered 
thunderstorms is expected Thursday afternoon, with a few strong-to-
severe storms possible across central Kentucky as sufficient 
instability will combine with slightly better shear as the low- and 
mid-level trough will be in closer proximity to the region by this 
time. Temperatures will be cooler Thursday afternoon with the front 
and additional cloud cover overhead, with highs only expected to 
reach the upper 70s to near 80. The storm threat will subside as the 
front clears the area Thursday evening, bringing cooler and drier 
air with it for Friday morning.

Friday and Saturday...

High pressure will settle into the Ohio Valley for Friday into 
Saturday, combining with mid-level NW flow to usher in drier weather 
for the end of the week and the first half of the weekend. Highs on 
Friday should reach the upper 70s to near 80, with lows Friday night 
falling into the mid-to-upper 50s. Highs Saturday will be near 
normal, with maximums generally expected to reach the low 80s. With 
dewpoints in the upper 40s and lower 50s both afternoons, expect 
comfortable conditions both days. Lows Saturday night should fall 
into the upper 50s to lower 60s.

Sunday into early next week...

Beyond Saturday, model solutions begin to diverge as the remnants of 
Hurricane Agatha begin to interact with the mid-latitude wave 
pattern across the eastern half of the Northern Hemisphere. WPC 
cluster analysis reveals that 30/12Z GEFS solutions are generally 
wetter for this time period, in line with the 31/00Z GFS 
deterministic run, while the 30/12Z EPS solutions are generally 
drier, which is in line with the 31/00Z ECMWF deterministic member. 
Since confidence is extremely low in any one solution at this amount 
of lead time, will stick with NBM temps and PoPs, which blends in 
information from multiple different guidance suites. In general, 
expect the warming trend which should begin Saturday to continue 
through Sunday and into Monday, with highs returning to above-normal 
levels. PoP chances will also slowly increase as we head into Monday 
and Tuesday as low- and mid-level moisture return should allow for 
typical afternoon shower/storm chances.

&&

.Aviation...(06Z TAF Issuance)
Issued at 110 AM EDT Tue May 31 2022

Sfc and upper ridging over the southern Appalachians will maintain 
dry weather through the valid TAF period. Expect VFR conditions with 
just scattered diurnal Cu, and light south winds at night increasing 
and veering to more of a SSW direction during the mixy part of the 
day. Gradient looks a bit tighter as you go north and west away from 
the high center, so included gusts just short of 20 kt in SDF and 
HNB this afternoon.


&&

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

$$

Short Term...RAS
Long Term...CSG
Aviation...RAS