Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 231703
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
103 PM EDT Thu Apr 23 2015

...Updated Aviation Discussion...

...Forecast Update...
Updated 1030 AM EDT Thu Apr 23 2015

Updated the forecast to make dewpt changes as locations over
southern Indiana have already dropped into the mid to upper teens.
Dry conditions are expected this afternoon with minimum RH values
ranging from the mid teens to lower 20s.  These dry RH values and
breezy winds (northwest between 5-15 mph with gusts to around
20mph), prompted some enhanced fire danger discussion amongst NWS
offices and our fire weather partners.  The general feeling is that
most ground fuels are still too wet to pose an enhanced fire risk,
but some patches of dry litter in wooded areas or fields that have
not yet greened up may still be susceptible to uncontrolled
burning.  Thus, issued an SPS for enhanced fire danger.

Otherwise expect a sunny day with highs in the upper 50s/lower 60s.

Updated 805 AM EDT Thu Apr 23 2015

Updated the forecast to remove the frost advy in effect this morning
which as expired.  Another frost advy is in effect for late tonight
into Friday morning as temps look to fall into the low to mid 30s
again with areas of frost formation likely.  Some locations in the
the Bluegrass region may drop as low as the upper 20s.

.SHORT TERM (Now through Friday)...
Issued at 300 AM EDT Thu Apr 23 2015

...Potential Frost/Freeze Again Tonight...

Lots to talk about in the short term for what would otherwise be a
quiet synoptic pattern. Currently, temperatures have fallen mostly
into the upper 30s and low 40s across the region, with a few
notorious cool spots already in the low and mid 30s. Patches and
some areas of frost are still expected through just after dawn.
Ongoing Frost Advisory for early this morning looks good.

Expect dry NW flow aloft today and tonight with surface high
pressure center settling over our area just after Midnight tonight.
Other than a few upper clouds across our SW today, sunny skies will
rule with highs in the upper 50s N to low 60s elsewhere. Steady NW
winds will be between 10 and 15 mph, with some gusts around 25 mph
or so through the afternoon.

There is fire weather concern for late this morning and this
afternoon. Soundings suggest potential for dry air mix down that
would yield dew points in the 15-20 range and dropping RH values
well below critical thresholds. However, winds and 10 hour fuel
moistures are more marginal so will hold off on further mention
other than in the main Fire Weather Forecast.

In coordination with surrounding offices, issued another Frost
Advisory for almost all of the CWA from 07-13z Friday morning.
Temperatures are expected to be slightly colder than what we
are currently observing as the surface high settles right over the
area and optimal radiational cooling should occur. Most areas should
settle into the mid 30s for several hours, with more localized areas
finding their way to the lower 30s. Not convinced we will see
widespread frost as the near-surface T/Td depression will be
notable, however Patchy/Areas certainly seems reasonable. Tossed
around the idea of a Freeze Warning across my far east counties as
data suggests these spots could fall below freezing for a few hours.
However, mainly think this will be in the sheltered and notorious
cool spots so not convinced it will be widespread enough to hoist a
Freeze Warning headline. Day shift can reconsider. Left out a few
counties around Bowling Green and the Tennessee border as some upper
cirrus looks to plague the area after Midnight.

Temperatures are expected to recover into the mid and upper 60s in
many spots Friday as brief upper ridging takes hold. Will begin to
see upper clouds stream overhead which may hold temps back just a
bit across the west. Otherwise, we`ll stay dry save for a few
showers possible around Bowling Green by early Friday evening.

.LONG TERM (Friday Night through Wednesday)...
Issued at 305 AM EDT Thu Apr 23 2015

Friday Night - Saturday Night...

Upper shortwave trof lifting out of the Desert Southwest on Friday
will spawn a surface low over the central Plains. Southerly flow
will deepen over the Ohio Valley, especially Friday night once a
shortwave ridge slips to our east. Expect precip chances to increase
dramatically through the night as isentropic lift develops. While
there are still some discrepancies in the exact timing and
placement, model consensus points to a decent band of showers
somewhere in the northern half of the forecast area prior to
daybreak Sat. Could be some elevated thunder, but low levels remain
very stable through this round.

Surface low will deepen to ~995mb over Missouri, but after that the
upper wave will shear out and the low will be guided ESE by the
closed H5 low over New England. Still some disagreement in the track
as the NAM takes the low along the I-64 corridor, while ECMWF tracks
along the KY/TN border. SVR potential bears watching, especially
south of the low track. Should be moderately unstable in the warm
sector, and mid-level lapse rates will also be quite impressive. Fat
CAPE is evident above 750 mb, so any storm that can punch through
the warm nose around 800mb will pose a hail and wind threat. Again,
the whole severe potential hinges on the surface low track, so stay
tuned. Will see quite a discrepancy in high temps, as south-central
KY should punch into the 70s while our Indiana counties struggle to
crack 60. Somewhere in between the gradient will be quite a bit
sharper than the current forecast can accurately reflect.

Precip chances will end from west to east on Sat night as the
surface low pushes east of the area. Still carrying a small chance
into Sunday across the Lake Cumberland area.

Sunday - Wednesday...

Cool and dry high pressure will prevail Sunday into Monday, with
temps running several degrees below late April normals. As we get
deeper into the week, we get into a split flow pattern which is
especially challenging with the broad closed low over the northeast
CONUS still blocking the pattern. POPs will ramp up Tue-Wed, but
we`ll limit them to 30-40% chance given the discrepancies in model
solutions.

&&

.AVIATION (18Z TAF Update)...
Updated at 100 PM EDT Thu Apr 23 2015

High pressure will dominate the region through the TAF period.
Northwest winds will be gusty at SDF/LEX this afternoon before all
TAF site winds go calm or light and variable late this evening.
Expect increased high and mid level clouds tomorrow ahead of the
next weather system.  Light winds will be predominantly from the
southeast tomorrow.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...FROST ADVISORY from 3 AM EDT /2 AM CDT/ to 9 AM EDT /8 AM CDT/
     Friday FOR KYZ023>043-045>049-053>057-062>067-074-076>078-
     081-082.

IN...FROST ADVISORY from 3 AM EDT /2 AM CDT/ to 9 AM EDT /8 AM CDT/
     Friday FOR INZ076>079-083-084-089>092.

&&

$$

Update.........AMS
Short Term.....BJS
Long Term......RAS
Aviation.......AMS





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