Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 210834

Area Forecast Discussion
National Weather Service Northern Indiana
434 AM EDT Wed Mar 21 2018

Issued at 428 AM EDT Wed Mar 21 2018

Snow will continue through mid morning for areas mainly south of
US 24 in east-central Indiana and western Ohio. Snow accumulations
are expected in these areas. Cool and dry northerly flow is
expected otherwise. Highs this afternoon will be in the upper 30s
and low 40s. Similar conditions are expected into Thursday and
Friday before the next system brings chances for rain and snow
later Friday night into Saturday.


.SHORT TERM...(Today and Tonight)
Issued at 428 AM EDT Wed Mar 21 2018

Short term forecast concerns center around morning snowfall amounts
and ending of pcpn. Energy transformation to east coast
getting underway early this morning as strong upper level jet rounds
base of trough across the mid south. Meandering upper low over the
Ohio valley will quickly translate east later today and deepen as
upper jet intensifies over the warm Gulf stream. GOES-16 water vapor
and IR images showing the early development nicely this morning.

Deformation zone on back side of departing upper low remains active
over our southeast as expected early this morning. However, very dry
air that has been in place has hampered westward expansion of snow.
Areas that have saturated have seen a quick drop in temperatures
into the upper 20s. Hires guidance have been struggling with this
interface of deeper moisture and drier air. Last several runs of
HRRR and RAP have been consistently overdone on QPF amounts. Earlier
01-04z runs were showing an axis of 0.5-0.6" total qpf from
Blackford northeast through southeast Allen and into Paulding OH.
Based on limited surface obs and MRMS regional radar qpe the
hourly hires QPF has been grossly overdone so far. Regional radar
mosaic does show a couple narrow bands of more intense snow
trying to wrap west but at same time dry air entrainment appears
to be hampering more widespread development. Still think there is
a window through sunrise for narrow banding to take place in and
just west northwest of current advisory but hires models likely
overdone. Have blended HPC qpf with hires for compromise and this
yields about 1 to 3 inches additional snow this morning. Few
webcams that can be seen have shown some light accums sticking on
roads but most accums have been confined to grassy surfaces.
Expect some slick roads this morning, especially those untreated
or less traveled where freezing will occur. Will be watching
trends in case further expansion of advisory is needed but for now
will handle with special weather statements.

Snow will quickly diminish this morning as upper energy transfers
east. Gradual clearing should follow today in the west and
eventually all areas by evening. Light winds and clear skies tonight
should allow good radiational cooling in the southeast over
snowpack. Lowered temps across snowpack to around 20 tonight with
upper 20s elsewhere.


.LONG TERM...(Thursday through Tuesday)
Issued at 428 AM EDT Wed Mar 21 2018

Below normal temperatures expected to continue for much of this long
term period though some glimmer of hope for warmer temperatures by
early next week. Dry weather expected through Friday evening though
a subtle short wave Thursday night into early Friday expected to
pass by to our south but will need to be watched for some light pcpn
far southwest. Otherwise main focus shifts to late Friday night and
Saturday with approach of mid level short wave and surface warm
front. Surface low associated with this system now expected to track
south of our area, likely through Kentucky, while also weakening as
it moves east. Warm air advection pcpn shield looks to spread well
north and east of surface low as warm front expands northeast.
Northern periphery of pcpn still in question depending on timing and
track of low but chances exist from around the US20 corridor south
and highest chances near and south of US24.

Pcpn type will also be tricky as atmosphere initially will support
snow north of warm front early Saturday morning but as sfc temps
warm transition to a wet snow or rain/snow mix possible as warm
front nears. A few inches of snow possible but with late March sun
angle and daytime warming will be difficult to get significant
accumulations on roads after mid morning.

Medium range models seem to be in agreement on a warming trend early
next week as yet another system tries to get organized in the plains
and moves northeast. Decent model agreement on this system and
warming but expected differences in critical details such as
frontal boundary location and timing of frontal waves. There is a
potential for some heavy rainfall near the frontal zone but much to
early to try and nail down any area. Will have to continue
monitoring trends next few days.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
Issued at 146 AM EDT Wed Mar 21 2018

VFR conditions expected at KSBN through the period, with mainly
gusty northeast winds becoming north-northwest and diminishing in
intensity by Wednesday afternoon. Otherwise, a tricky forecast at
KFWA with the surface low and associated deformation zone to our
southeast. KFWA is right on the far western edge of where we expect
the moderate snow to be tonight into tomorrow morning. Some of the
models bring the more moderate intensity bands just east of KFWA,
while others bring it right over the terminal. Looking at upstream
obs, the bands expected to potentially reach the terminal are
leading to low-end MVFR conditions. Just east of there in the better
forcing, we have IFR and even some LIFR conditions (as close as
AOH/Lima, OH). For now, went on the conservative side and kept the
TAF low-end MVFR at BKN025 and 3SM visibility. Given lower
confidence, I put this in a tempo group. I expect the VLIFR
conditions to stay southeast of the terminal, but will monitor
observational trends closely and adjust the forecast to bring more
pessimistic conditions further northwest if needed. Winds at the
terminal will continue gusting into the mid 20 knot range, but
will gradually die down as the pressure gradient slackens
Wednesday afternoon.


IN...Winter Weather Advisory until 10 AM EDT this morning for INZ034.

OH...Winter Weather Advisory until 10 AM EDT this morning for OHZ025.

LM...Small Craft Advisory until 8 AM EDT Thursday for LMZ043-046.



SHORT TERM...Lashley
LONG TERM...Lashley

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