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Area Forecast Discussion (AFD)

Issued by Louisville, KY (LMK)

FXUS63 KLMK 171100

Area Forecast Discussion
National Weather Service Louisville KY
700 AM EDT Mon Jun 17 2019

...Updated Aviation Discussion...

.Short Term...(Today and tonight)
Issued at 320 AM EDT Mon Jun 17 2019

Juicy and boundary-rich environment in place for the short-term, and 
the main challenge will be placement and coverage of more 
convection. Stratiform precip that lingered behind Sunday evening's 
storms has now largely dissipated, but new convection has developed 
near the Kentucky/Tennessee line, and it remains to be seen how 
sharply that will cut northward. Impacts will be an even bigger 
deal, as copious amounts of rain fell mainly along and north of 
Interstate 64, and 1-hr FFG in some of those areas is now less than 
1 inch. 

Hi-res models have been struggling at times with run-to-run 
consistency, but do show the current storms over south-central KY 
lifting NE and intensifying as they get north of the Parkways later 
this morning. Synoptic-scale models paint with a broader brush, and 
show storms re-igniting this afternoon over the same locations where 
some of Sunday's heaviest rain fell. These are usually overdone, but 
hard to write off completely in this environment, and given the very 
low FFG, will carry a Flash Flood Watch for roughly the northern 
half of the forecast area. Another wave will kick through late 
tonight into Tuesday morning, so will continue the watch through 
at least midday Tuesday. Not expecting a repeat performance of 
Sunday hailers as any CAPE today is of the tall and skinny variety.

.Long Term...(Tuesday through Sunday)
Issued at 330 AM EDT Mon Jun 17 2019

...Unsettled Pattern Continues...

The longterm starts off wet as a shortwave moving through a zonal 
pattern pushes out of the Mississippi Valley and into the Ohio 
Valley that continues to lie south of a quasi-stationary boundary 
and within a moist and conditionally unstable environment. Scattered 
showers and thunderstorms ahead of this shortwave will continue 
potential flood concerns, therefore the Flash Flood Watch will 
remain valid until midday Tuesday. Models generally agree that 
precipitation chances should begin to wane by early Wednesday 
morning with dry conditions through much of the day. The Euro model 
is advertising a chance of light rain throughout the day, but the 
GFS and CMC keep any showers/storms at bay until Wednesday late 
afternoon/evening. Severe potential exists late Wednesday into early 
Thursday morning with SBCAPE values ranging from 2500 to almost 4000 
J/kg across the area accompanied by modest deep layer shear. But 
increased southwest flow will see PWATs return to close to 2.00 
inches, which will once again turn our focus toward potential flood 
issues. Models suggest a much need drying out for much of Friday. 
Precipitation totals through Friday range from 2 to 4 inches, though 
the convective nature could see localized areas receiving much less 
or much more. 

By Friday evening, long range models begin to diverge. The Canadian 
and Euro models continue dry conditions through Saturday, whereas 
the GFS advertises another shortwave bringing showers and storms 
back by Friday night through Saturday. Models come back into 
agreement for a wet Sunday and Monday.


.Aviation...(12Z TAF Issuance)
Updated at 655 AM EDT Mon Jun 17 2019

Initial challenge will be any persistence of scud, which previously 
brought in a brief IFR ceiling at LEX and HNB. Recent trends have 
been for it to scatter out to not being mentioned in those sites, 
though SDF is still carrying a FEW003. Will initialize VFR, with 
high-end MVFR at HNB. 

Forecast confidence remains low as it is a moist and boundary-rich 
environment, with plenty of questions as to which boundaries will 
fire. One current band of precip north of I-64 and another across 
central Kentucky are not affecting any of the terminals at this 
time. Destabilization will be limited but can't rule out mentioning 
VCTS in any of the terminals this afternoon. 

Another wave coming through the Ohio Valley later tonight will bring 
increasing rain chances toward daybreak on Tuesday. Will limit 
thunder mention to VCTS, with MVFR ceilings dropping into fuel-
alternate at all sites except LEX.


IN...Flash Flood Watch through Tuesday afternoon for INZ076>079-083-

KY...Flash Flood Watch through Tuesday afternoon for KYZ025-029>043-



Short Term...RAS
Long Term...CG