Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 042248
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
548 PM EST Wed Mar 4 2015

...Forecast Update...
Issued at 545 PM EST Wed Mar 4 2015

Precipitation has changed over to basically all snow northwest of the
Ohio River, with Louisville transitioning to all snow prior to 6
pm. Frankfort currently has snow and Lexington will switch to
snow by 7 pm.

Snow will intensify through mid evening across southern Indiana and
along the Ohio River as decent radar returns are approaching
Jefferson County Ky. Overall, snowfall totals across our forecast
seem on track at this point.


.SHORT TERM (Now through Thursday Night)...
Issued at 301 PM EST Wed Mar 4 2015

...Winter Storm Still on Track Tonight...
...Bitter Cold Friday Morning...

First, though, will likely go ahead and let the Flood Watch expire
on time at 7pm EST/6pm CST.  Only light rainfall amounts are
expected for the rest of the afternoon/evening and any ongoing minor
flooding can be handled with short term products.

Cold air is coming into the region as arctic high pressure enters
the from the northwest.  The rain changed to sleet and then snow
earlier this afternoon north of the Ohio River, with the changeover
continuing to move to the southeast late this afternoon and this
evening.  Frontogenetical forcing, our location near the right
entrance region of the upper jet, deep moisture, significant
isothermal layer and good dendritic growth on soundings, and some
weak low level instability all point to widespread snow tonight.
Snow amounts are never easy to nail down, but in general, after
chatting with neighboring offices, we have remained fairly
consistent with the amounts we`ve been advertising since last night.
There will be some banding with this event, and anyone getting
caught under a band will see strong snowfall rates and, as a result,
higher amounts.  The best chance for heavy banding appears to be
roughly from the northern Blue Grass through the Nolin and Rough
River Lake areas.

We have pulled back a bit on glaze in the south tonight.  In
southern Indiana the changeover has been primarily from rain to
sleet to snow, and model progs in southern Kentucky this evening
support that idea.  Some ice will still be possible, but should be
less than a tenth of an inch.

Low temperatures tonight will generally be in the teens...perhaps
around 20 in the Lake Cumberland region.

On Thursday the storm system will pull off as the arctic high
advances from Iowa to Illinois.  In southern Indiana significant
snow should be done before the sun rises, with snow tapering off
from northwest to southeast during the early and mid morning hours
in Kentucky.  Could see a few lingering flurries into the afternoon
as clouds slowly break up.  With clouds in the sky and snow on the
ground, and northerly surface winds, went cooler than guidance for
highs.  Didn`t goo *too* cool, though, since we could get some
partial March sunshine in the afternoon.  Given this, temps landed
in the lower and middle 20s for highs.

Tomorrow night that high will continue to invade, and will be
centered right over the Ohio River at 12Z.  This will lead to calm
winds and mostly clear skies.  With those factors plus deep fresh
snowcover, went well below guidance for lows, keeping in line with
previous forecasts in the single digits either side of 0. That`s
about 30 degrees colder than normal.

.LONG TERM (Friday through Wednesday)...
Issued at 230 PM EST Wed Mar 4 2015

...Spring-like Temperatures On the Way...

Friday - Saturday...

Sfc high pressure will settle into the region for Friday/Saturday
resulting in dry conditions.  The main forecast challenge will then
be temperatures over the snowpack.  After a potentially record
setting cold Fri morning, temperatures will struggle to reach the
mid to upper 20s Friday afternoon with perhaps some locations over
far south central KY in the Lake Cumberland region reaching lower
30s.  If the Lake Cumberland region receives a thicker snowfall,
they may not make it out of the upper 20s Fri afternoon either.

Friday night into Saturday, temperatures look to moderate some as
troughing/NW flow flattens over the Ohio Valley.  Expect low temps
Sat to range between 10-17 degrees and highs on Sat afternoon to
rise above freezing into the mid and upper 30s with some locations
potentially reaching 40 degrees.

Although sunshine on Friday should help melt snow off of dark
surfaces like pavement, Saturday should be a better melting day area
wide as temps rise above freezing.

Sunday - Wednesday...

The GFS tries to bring a very small amount of precip into our area
from a disturbance passing to our north on Sunday, but moisture
profiles seem too shallow for precipitation.  Thus, will continue
with increased clouds and no POPs.

The bigger story for next week is a big warm up for the Ohio Valley
taking temperatures back to around normal.  The upper level pattern
will flatten over the CONUS early next week helping temps to
moderate over our region as thicknesses steadily rise.  In addition
a more active southern stream should help push warm air into the
Ohio Valley starting Tues.  Some rain chances look to occur in the
Tues-Thurs time frame next week although models are in disagreement
as to when and how much rain we will receive mid week next week.
Therefore will continue 20% POPs in that time frame.  One thing that
long range models are in agreement with is high temperatures
reaching the 50s and perhaps low 60s Tues-Thurs next week!

&&

.AVIATION (00Z TAF Update)...
Issued at 1210 PM EST Wed Mar 4 2015

Complex winter system moving through the Ohio Valley today into
tonight which will continue to bring IFR to LIFR conditions.

KSDF:
Already getting reports of sleet mixing in around the Louisville
metro, so will initialize KSDF with -RAPL.  Will transition to -SNPL
at 19Z, going to all snow by 22Z.  Think vsbys within the snow will
likely be 1/2SM or less given the expected high intensity.  Cigs may
bounce over the next few hours between IFR and MVFR, but think IFR
cigs will be the most prevalent.

KLEX:
Will bring -RAPL into KLEX by 20Z, transitioning to all snow by
23Z.  The snow will be heavy once it transitions, so vsbys 1/2 to
1/4 of a mile are likely for a long duration tonight.  Cigs will
be IFR, perhaps high-end LIFR at times.

KBWG:
Will continue with -RA through 23Z, before bringing in -RAPL.  Sleet
will likely last a few hours longer at KBWG, transitioning to all
snow by 02Z.  The best forcing looks to pass just north of KBWG, so
will not hit the vsbys quite as hard with this package, but LIFR
vsbys are still likely.

All sites will slowly improve through Thursday morning as the snow
ends and cigs begin to rise.  Winds will be out of the north through
the period around 10 knots.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...WINTER STORM WARNING until 1 PM EST /Noon CST/ Thursday FOR
     KYZ023>043-045>049-053>057-061>065-070>072.

     FLOOD WATCH until 7 PM EST /6 PM CST/ this evening FOR
     KYZ023>043-045>049-053>057-061>067-070>078-081-082.

     WINTER STORM WARNING until 1 PM EST /Noon CST/ Thursday FOR
     KYZ066-067-073>078-081-082.

IN...WINTER STORM WARNING until 1 PM EST /Noon CST/ Thursday FOR
     INZ076>079-083-084-089>092.

     FLOOD WATCH until 7 PM EST /6 PM CST/ this evening FOR INZ084-
     089>092.

&&

$$

Update.........JSD
Short Term.....13
Long Term......ZBT






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