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FXUS63 KLMK 221626

Area Forecast Discussion
National Weather Service Louisville KY
1126 AM EST Mon Jan 22 2018

.Forecast Update...
Update 1123 AM EST Mon Jan 22 2018

...Gusty Winds and Showers...

Widespread rain showers, mostly light, are pushing east across the 
CWA. A steadily weakening trend has been noted, and expect this to 
continue. Still, everyone should expect at least some rain so will 
keep pops in the categorical range. Around a quarter of an inch in 
most spots is still a reasonable bet. 

The main focus as we head into the afternoon will be chances for 
redevelopment of showers just ahead of the cold front. We'll have to 
watch this potential closely because the 45-50 knot low level jet 
will still be in place and if we get some destabilization from the 
dry slot our low level lapse rates could steepen and allow us to mix 
down the stronger winds from that layer. The latest HRRR runs are 
pretty bullish with the redevelopment along the I-65 corridor 
pushing east late this afternoon early evening, and given the exit 
region jet dynamics combined with the surface front it seems 
reasonable. That being said, the other hi-res models seem to 
struggle with redevelopment some. So, low confidence on exactly how 
it will evolve this afternoon, but higher confidence that if we do 
get some showers gusty winds of 40 mph or greater aren't out of the 


.Short Term...(Today through Tuesday)
Issued at 255 AM EST Mon Jan 22 2018

Bowling ball upper low making its way across Kansas will catch up to 
its sfc reflection later today, and the system will become 
vertically stacked over NW Missouri this evening before heading ENE 
into the Great Lakes tonight. Warm conveyor belt is well established 
from the ArkLaTex up into the Ozarks, and will translate eastward 
across the Ohio Valley today.  

Have gone with categorical POPs across the region for today, with 
the best precip chances late this morning into early afternoon along 
and west of I-65, and later in the afternoon farther east into the 
Bluegrass region and along the Cumberland Escarpment. QPF for this 
event is fairly modest, averaging around a quarter inch. Thunder 
remains a low probability, but there is some weak elevated 
instability so we will include a slight chance for embedded thunder. 
Not a huge difference in probabilities when all is said and done, 
but confidence is a bit higher south of the Western Kentucky and 
Bluegrass Parkways. 

Temps will be relatively flat through the day today, staying in 
the 50s to lower 60s. Bigger story will be the wind later this 
afternoon and tonight, as the wind fields are fairly robust. 
However, with the strongest cold advection aloft coming during the
night, that will limit the gustiness, but still could see gusts 
in the 30-40 mph range. 

Not much temp recovery is expected on Tuesday under lingering upper 
trofiness behind the departing cyclone. Most of the wraparound 
moisture will stay to our north, but held on to slight chance POPs 
over the Bluegrass region late in the day as the low-level flow 
turns more northwesterly.

.Long Term...(Tuesday night through Sunday)
Issued at 255 AM EST Mon Jan 22 2018

Fairly progressive pattern through the middle of the work week. 
Initially deep cyclonic curvature could keep some lingering precip 
over the Bluegrass into Tuesday night, and that could end as 
flurries if it persists long enough. However little or no impact is 

Temps near seasonal normals Tue night and Wed, with a warming trend 
for the latter half of the week as we trend into low-amplitude upper 
ridging, and southwesterly low-level flow behind a departing sfc 

Next precip chance ramps up Fri night and stays with us for much of 
the weekend as the pattern amplifies enough to get a good Gulf 
moisture tap. Temps are mild enough for this to be an all-rain 
system, but moist adiabatic profiles are too stable for any thunder 
threat. Capped precip chances in the likely category mainly to 
account for timing uncertainties. Otherwise rain at some point 
during the weekend is close to a slam-dunk. GFS and ECMWF both 
currently show a "clean" frontal passage, but other runs have shown 
the potential for a secondary sfc wave that could hang the front up 
enough for precip to persist longer and perhaps even end as snow. 
Sunday forecast will mention mixed precip, but it's a low-
probability forecast at this point.


.Aviation...(12Z TAF Issuance)
Issued at 618 AM EST Mon Jan 22 2018

Strong low-level southerly winds in place this morning ahead of a 
cold front and associated rain band. Moderate rain has spread into 
far western KY/southeastern IL and will reach OWB/EVV within the 
next hour. For the most part, VFR ceilings are expected today. 
However, expect a lowering with the rain band and especially right 
after the rain. Enhanced low-level moisture will likely result in 
Fuel Alternate at HNB this afternoon. Did include a period of high-
end MVFR at BWG this afternoon as well. SDF could see temporary MVFR 
around 21z (and LEX around 00z), but confidence in prevailing MVFR 
is low at those two sites. 

Peak southerly gusts today should reach 25-30 kts, with winds 
veering southwesterly this evening. The rain won't last all that 
long at any one site, but a secondary band of showers may be able to 
develop after 21-22z right along the surface cold front. This band 
would push through LEX shortly after 00z. We'll see a period of 
clearing where clouds go SCT late this evening and tonight as a dry 
slot works in behind the front. But additional low ceilings will be 
possible Tuesday morning as clouds work back in from the northwest.




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