Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 171847
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
147 PM EST Sat Feb 17 2018

...Slick Travel Conditions in Southern Indiana and Northern
Kentucky This Afternoon...

.Forecast Update...
Issued at 145 PM EST Sat Feb 17 2018

Light to moderate snow showers continue along and north of a line
from Hancock County to Franklin County. South of the Ohio River, we
are seeing rain mix in with the snow at times. However, multiple
traffic issues were reported along I-64 in Shelby County and eastern
Jefferson County. Just issued a short-term Winter Weather Advisory
for hazardous travel through the rest of the afternoon.

Mesoscale banding has put down 1 to 2 inches of snow already across
parts of southern Indiana. Steady precip has kept temperatures cold
enough for all snow in these areas. Along and south of the river,
additional accumulations should be limited to a dusting. But some
slick spots on area roads will be possible. Road sfc temps are
relatively warm in the mid to upper 30s, but moderate rates have
easily overcome this. Travel is particularly hazardous just north
and west of Louisville, including Indiana counties like Crawford,
Harrison, Floyd, and Clark. As of this writing, moderate snow
continues in these areas. Will continue to assess impact potential
from snow further east and expand if necessary this afternoon.

&&

.Short Term...(This afternoon through Sunday evening)
Issued at 206 AM EST Sat Feb 17 2018

Surface analysis early this morning showed high pressure sprawled
across Illinois, Indiana, and Ohio. Latest IR satellite imagery
depicted a blanket of stratus across southern Indiana and central
Kentucky while high clouds were spreading east into the region.
Regional radar all clear and with light north/northeast winds,
readings were in the 30s, near 40 closer to the KY/TN border.

The main focus in the short term is for today`s rain as a southern
stream system quickly spreads across the region. The latest guidance
including hi-res models is in good agreement showing precipitation
spreading in from the southwest after daybreak, peaking in the
mid/late morning through early/mid afternoon before exiting the area
late this afternoon. No significant changes were made to the
precipitation chances from the previous forecast other than blending
the hourly forecast with the latest guidance.

Looking at surface temperatures and forecast soundings, there`s
still potential for precipitation onset to be a mix of rain and
snow, generally along/north of the I-64 corridor with temperatures
initially in the 32-35 degree range. Little if any snow accumulation
is expected as ground temperatures are warm and daytime accumulation
is harder to achieve. By late morning, precipitation is expected to
be all rain. Nonetheless, wouldn`t be surprised to see some wet
snowflakes mixed in where precip bands are the heaviest.

Total rainfall amounts are expected to vary from less than 1/4 of an
inch across southern Indiana, then 1/2 to 3/4 of an inch across
southern Kentucky. While heavy rain is not anticipated, across
southern Kentucky these amounts could cause some additional rises on
rivers, streams, and creeks given the recent wet spell and saturated
soils.

High temperatures today won`t vary too much from morning readings
with the precipitation and clouds around. Plan on highs to top out
in the lower to middle 40s while some spots across the northern
Bluegrass could stay right around 40.

Clouds will clear out later this evening and tonight as high
pressure moves directly over Kentucky. With the light winds,
clearing skies, and recent rainfall, added patchy fog to the
forecast. Lows will fall into the lower 30s.

Sunday is still shaping up to be a dry day with highs in the 50s and
a mix of sun and clouds.

.Long Term...(After midnight Sunday night through Friday)
Issued at 225 AM EST Fri Feb 17 2018

...Increasing Potential For River Flooding Next Week...

Highly anomalous weather pattern is still poised to set up across
the lower Ohio Valley next week bringing threats for heavy rain,
river flooding, and potentially record warm temperatures to parts of
Kentucky and southern Indiana.

By Monday, the upper level pattern is expected to feature a building
southeast US ridge while troughing digs across the southwest US. The
southwest flow in between will allow an axis of highly anomalous
Gulf moisture to stream north/northeast through the mid-Mississippi
and lower Ohio Valleys. 17.00z GFS PWATs ranged from 1.2 to 1.4
inches across portions of Indiana and Kentucky Monday through
Wednesday, which is near records for mid/late February at
ILN/BNA/ILX.

The first wave of precipitation comes late Sunday night through
Monday as the warm front lifts north across the region with the
highest precipitation chances after midnight through noon on Monday.
Depending on how quickly the warm front surges north, temperatures
Monday will warm well into the 70s across Kentucky with highs
currently forecast near 75 degrees across southern Kentucky.

Monday night through Tuesday should be mainly dry and near record
warm. 17.00z guidance points to 850 mb temperatures reaching +10 to
+14C, which is 2-3 standard deviations above normal. Blended
guidance puts highs in the mid to upper 70s, but wouldn`t be
surprised if this trends higher and portions of southern Kentucky
and parts of the Bluegrass surge to 80 degrees if clouds clear out.
Current forecast already hits or exceeds record temperatures for the
day (just set in 2016 or 2017) and the all-time February record is
81 for Louisville (set in 2017).

The bulk of the heavy rain axis Tuesday into Tuesday night looks to
stay just northwest of the forecast area, though we`ll have to watch
portions of southwest Indiana which may be clipped. By Wednesday,
guidance points to the front slipping through Kentucky bringing
widespread rain and possibly a few thunderstorms to the area.

Total rainfall amounts forecast for Monday through Wednesday came in
lower across southern and southeast Kentucky with totals around 1
inch. Across southern Indiana, especially southwest Indiana, totals
of 2 to 3 inches are still forecast. With the ongoing rises on
rivers, this additional rainfall could cause further rises on small
river basins, streams, and creeks and extend the rises on the main
stem Ohio River which is forecast to rise into minor flood stage
next week.

More rainfall could fall Thursday into next weekend as models show
another frontal boundary stalling near the region. Still lots of
time to hone in on where the heaviest axis of rain will fall, but
the overall forecast regarding flooding is not very optimistic.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1245 PM EST Sat Feb 17 2018

An upper wave crossing the Ohio and Tennessee Valleys today will
continue to bring snow to HNB/SDF and mainly rain to LEX/BWG this
afternoon.  LEX may see a few flakes mix in as well.  The rain/snow
line will be very close to LEX and may need to amend late this
afternoon. Precipitation should be light to moderate at times
causing IFR and possibly lower conditions at times.  Precipitation
should end this evening with IFR cigs sticking around and perhaps
some evening VCSH at HNB/SDF.  Low clouds will clear the area from
west to east late tonight into tomorrow morning with VFR conditions
returning by tomorrow morning.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory until 7 PM EST /6 PM CST/ this evening
     for INZ076>079-083-084-089>092.

KY...Winter Weather Advisory until 7 PM EST this evening for
     KYZ030>034.

&&

$$

Update...EBW
Short Term...ZT
Long Term...ZT
Aviation...AMS



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