NWS Area Weather Forecast Discussion
Louisville, KY

FXUS63 KLMK 160514

Area Forecast Discussion
National Weather Service Louisville KY
1214 AM EST Sat Feb 16 2019

...Updated Aviation Discussion...

.Forecast Update...
Issued at 940 PM EST Fri Feb 15 2019

Latest Doppler radar trends shows that precip has really diminished
over southern IN and the northern half of central KY at this time.
Note that cloud bases rose after the initial northern band of snow
dissipated. Meanwhile, KY Mesonet obs show temps have been quasi-
steady lately over central/south-central KY, with values 33-35 over
south-central KY and mid-upper 30s in our far southeastern counties
where no Advisory exists. BWG has been reporting light rain, and we
have received reports of mixed precip at times where radar shows
higher returns over south-central KY now.

Meanwhile, the St. Louis and Evansville radars show more precip
still to the west of us, with a slight drift north of east. This
could suggest that some light snow could again move into parts of
north-central KY and perhaps into south-central IN later this
evening/overnight. The new 00 UTC NAM12 and NAM3 along with latest
HRRR models pick up on this, with the northern edge of measurable
precip roughly from Hancock/southern Perry counties eastward to
south of I-64 to about Lexington, with higher amounts south of that

With current trends and the latest high res model output, it seems
prudent to cancel the Winter Weather Advisory for a row of counties
on its northern edge. This includes Dubois, Crawford, Harrison, and
Floyd counties in Indiana, and Jefferson (including Louisville),
Shelby, Franklin, Scott, Bourbon, Nicholas, and Harrison counties in
central Kentucky. Will keep Advisory for Lexington for now pending
latest radar trends later this evening into the overnight.
Meanwhile, based on current surface temps and forecasted lows
overnight over our far southeastern counties, see no real reason to
expand Advisory into those 5 counties near the TN border.

Overall, made some adjustments to POPs and QPF amounts overnight.
Improvement occurs on Saturday.


.Mesoscale Update...
Issued at 645 PM EST Fri Feb 15 2019

Latest radar shows that precip has overspread our forecast area and
will reach the ground in all areas in central KY shortly. There has
been a small northern band of snow for the last hour or so bringing
temporarily lower visibilities/rates than what models suggested but
will likely weaken and not affect the current Advisory. A tight
gradient to flurries or nothing exists over our eastern counties in
south-central IN as expected.

A more persistent band of precip with higher reflectivity returns
exists over our west-central KY counties. Within this band, current
dual pol correlation coefficient (CC) data suggests that a mix of
precip or varying types is likely occurring from Grayson and Hart
counties southward. Expect precip to continue for the next several
hours across central KY. No forecast changes at this time.


.Short Term...(This evening through Saturday)
Issued at 310 PM EST Fri Feb 15 2019

...Minor Snow Accumulations Tonight...

Broad snow shield taking shape across Missouri and parts of southern
Illinois ahead of an upper shortwave trof moving quickly eastward
across Kansas. Snow to rain/freezing rain transition lays out from
the Ozarks into the Missouri Bootheel. The area of snow will pivot
eastward across the Ohio Valley later this evening as the upper
impulse scoots through, producing 1-2 inch accumulations, perhaps
with some locally higher amounts.

Confidence in the snow forecast is decreasing, especially along the
northern edge, because the sfc reflection appears weaker and farther
south. The greatest accumulations will be roughly along a line from
Hartford to Elizabethtown to Richmond, but there could be localized
totals of 2 inches or more within that area. Best window for
accumulations still looks to be late evening to shortly after
midnight, likely with a period of moderate snow that will cover even
treated roadways.

Will clip a few counties out of the Winter Weather Advisory north of
Interstate 64 even though they could still see a dusting to a half
inch. Dubois County is tricky given a much colder start this
morning, which makes impacts more likely from otherwise meager
snowfall. Will cover the cancelled areas with a Special Weather
Statement. Southern edge will be kept as-is, given that we still
stand to lose ice aloft after midnight, leading to a period of
freezing drizzle.

The precipitation is expected to quickly move east of the forecast
area by dawn Saturday. Recovery in temps during the day will be slow
at first due to cloud cover, but should rise above freezing by
midday and touch 40 in the afternoon.

.Long Term...(Saturday night through Friday)
Issued at 330 PM EST Fri Feb 15 2019

The weather starts dry late on Saturday evening, but that looks to
change during the early morning hours of Sunday. Weak upper level
ridging gives way to a compact wave over the Missouri Valley. An
easterly sfc wind will be maintained with overrunning precip
developing between 06-12z Sunday. Temperatures are forecast to be
fairly steady in the low to mid 30s Sunday morning over the northern
half of the area, with the southern half of the area warming into
the upper 30s/low 40s. So still looking at a brief wintry mix
possible over the northern half of the area to start the day, but
accumulations are unlikely at this point. Temperatures continue to
rise through sunrise, with all rain in southern Indiana by 15z or
so. The rest of Sunday looks to feature some light rain, especially
east of I-65 during the afternoon. Afternoon highs will be in the
40s to low 50s.

A period of dry weather is still likely Sunday night through Monday
night, possible Tue morning. Highs on Monday are shaping up to be in
the low to mid 40s. Heights amplify over the eastern U.S. during
this period in response to a substantial trough over the
Intermountain West. This robust wave will eventually pivot northeast
toward the Upper Midwest. Meanwhile, an effective warm frontal
boundary should set up near or perhaps just south of central KY
(models differ somewhat). The axis of heaviest rain will shift
between now and then, but there is potential for moderate to heavy
rain Tuesday afternoon through Thursday. Forecast confidence is very
low beyond next Thursday.


.Aviation...(06Z TAF Issuance)
Updated at 1215 AM EST Sat Feb 16 2019

Have had a couple of reports of sleet near BWG this past hour, but
expect a mix of rain or sleet the next couple of hours before a
brief transition to freezing rain and then drizzle. Only other site
likely to see impactful weather is LEX, with potential an MVFR light
snow. Winds will be from the north and slowly transition to
northeast during the day...with the northern sites possibly seeing
clear skies. BWG probably will hang on to some lower clouds longer.


IN...Winter Weather Advisory until 6 AM CST Saturday for INZ089.

KY...Winter Weather Advisory until 7 AM EST /6 AM CST/ this morning
     for KYZ023>029-038>041-045>049-053>057-061>067-070>072-074-



Short Term...RAS
Long Term....EBW

Forecast Discussion from:
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