Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 211202

Area Forecast Discussion
National Weather Service Louisville KY
802 AM EDT Wed Mar 21 2018

.Forecast Update...
Issued at 802 AM EDT Wed Mar 21 2018

Went ahead an upped totals for an area stretching from Salem, IN
down through New Albany, Louisville, and Bardstown. A persistent
moderate-heavy snow band has set up and persisted with at least 1"
per hour rates. Now seeing widespread amounts between 6 and 8" in
the warning area, with locally higher amounts possible. Expect an
additional 1 to 2 inches on top of what has already fallen.

Decided to add Nelson and Spencer counties into the warning since
the band is now stretching down into that area. Expect storm totals
in the 4 to 6 inch range down there.

Issued at 649 AM EDT Wed Mar 21 2018

Will keep all of the headlines going for now this morning as light
snow continues to rotate around the parent upper low. Snow is mostly
light, although a few moderate bands are occurring. Most notably is
a moderate band stretching from Salem, IN down through New Albany,
Louisville, and near Bardstown. Seeing close to 1 inch per hour
rates with this feature. With snow expected to persist through the
morning hours, additional amounts between a coating and 2 inches are
possible, although areas west of I-65 will likely see less than 1
inch of additional accums.


.Short Term...(Today through Thursday)
Issued at 310 AM EDT Wed Mar 21 2018

...Snow Accumulations Continuing This Morning...

Upper low is now centered over east central Kentucky, and will very
slowly move SE toward the Appalachian spine by midday. As this
occurs, light to occasionally moderate, snow will continue in
response to mid level deformation. Have been seeing accumulations
around a half an inch per hour, and with several hours of snow still
to go, 1 to 3 inches is still expected on top of what has already
fallen across the area. Recently expanded the Winter Storm Warning a
bit further SW where storm totals should range between 3 to 5
inches. Across the original Warning area, totals should range
between 4 to 6 inches, with locally higher amounts up to 8 inches
possible. Elsewhere across the Advisory areas, storm total snow
amounts should range between 1 to 4 inches.

Temps have now fallen to around or just below freezing and will
remain that way until just after sunrise when they try to warm a few
degrees above freezing. As a result, have seen side and untreated
roads deteriorate over the past couple/few hours. The morning
commute will likely be impacted with snow continuing to fall and
temps just below freezing. Use caution and allow extra time this
morning. Also watch for downed trees limbs due to the heavy wet
snow. Have already seen a report of that in the Louisville metro.

Snow should end around midday to early afternoon from W to E with
highs ranging from the mid 30s to low 40s. Will keep the current
headlines going until 18z.

Tonight - Thursday...

Surface high pressure and dry NW flow aloft will take hold. This
will bring a brief period of dry conditions before more weather
makers arrive for the weekend. Expect cold overnight lows in the low
to mid 20s, with highs on Thursday mostly ranging in the 45 to 50
degree range.

.Long Term...(Thursday night through Tuesday)
Issued at 310 AM EDT Wed Mar 21 2018

...Active weather pattern to continue with a few weather systems
that could have impact...

Thursday night...

The long term starts out with NW flow aloft sandwiched between a
ridge over the central U.S. and a deep trough over the northeastern
U.S. Within this NW flow, models continue to show a weak shortwave
diving SE across the lower OH Valley Thursday night. At this point,
most data is looking pretty weak with any precipitation across our
CWA. Will just mention a slight chance of rain or snow for now. Lows
will range from the upper 20s in the east to the mid 30s in the west.

Friday night through Saturday night...

A storm system will move out of the central Plains and into the Ohio
Valley as we enter the weekend. As this occurs, a large
precipitation shield will overspread the area. Precipitation type
looks to be mostly rain, with some thunderstorm potential also
possible. However, a tight temperature gradient will exist on the
north/northeast side of the precipitation shield to the point where
some mixed precipitation could come into play. Will have to keep an
eye on this trend in the coming days. Overall, rainfall amounts
could range between a half and 1 inch, with locally higher amounts.

Lows on Friday night will range from the low 30s NE to the low 40s
SW. Highs Saturday should jump to the upper 50s SW, but only reach
the low to mid 40s NE. A 10 degree temps spread form NE to SW will
continue into Saturday night ranging from mid 30s NE to mid 40s SW.

Sunday - Early next week...

We should dry out on Sunday as the storm system quickly pushes off
the mid Atlantic coast, and upper ridging tries to take hold. Highs
should recover to the 50s by Sunday afternoon.

As we head into the early part of next week the upper ridge axis
will try to hold on, but will still make slow progress eastward over
the area. SW flow through a deeper column will develop to our west
between the upper ridge axis and a cutoff low over the SW CONUS. A
deep Pacific/Gulf plume of moisture will setup between those two
features and then try to spill into the Ohio Valley as we approach
mid week. This could be the beginning of a wet period, but will have
to see how the details shake themselves out. Will stay a bit
optimistic with only low chances for precip Monday with potential
that the upper ridge hangs tough for a bit. However, rain chances
become higher by Tuesday as the upper ridge axis begins to lose
influence over our area.

Highs should be in the upper 50s and low 60s with milder lows in the
mid 40s by early next week.


.Aviation...(12Z TAF Issuance)
Issued at 625 AM EDT Wed Mar 21 2018

Ongoing snow and stratus are contributing to low cigs/vis across the
region. The worst conditions have generally been across southern
Indiana and north-central Kentucky this morning. Models show the
snow sticking around for most areas through sunrise, with some
clearing starting in western fringes of the CWA (near HNB) in the
next hour or two. The drier air and will gradually push eastward
through the day, and we should see VFR conditions everywhere by
sunset with mostly clear skies overnight.


IN...Winter Storm Warning until 2 PM EDT /1 PM CDT/ this afternoon
     for INZ076>079-084-089>092.

     Winter Weather Advisory until 2 PM EDT this afternoon for INZ083.

KY...Winter Storm Warning until 2 PM EDT /1 PM CDT/ this afternoon
     for KYZ024-025-028>034-038-045.

     Winter Weather Advisory until 2 PM EDT /1 PM CDT/ this afternoon
     for KYZ023-026-027-035>037-039>043-046>049-053>057-061>067-



Short Term...BJS
Long Term...BJS
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