Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 171726

Area Forecast Discussion
National Weather Service Northern Indiana
1226 PM EST Sun Feb 17 2019

Issued at 243 AM EST Sun Feb 17 2019

An upper level system will spread light snow across the area this
afternoon with snowfall amounts of 1 to 3 inches. Highs this
afternoon will range from 25 to 30. Monday and Tuesday will be
dry with moderating temperatures.


.SHORT TERM...(Today and Tonight)
Issued at 243 AM EST Sun Feb 17 2019

Wrapped up upper low over NE will open up across IA this aftn before
lifting out rapidly through the ern lakes by Mon morning. Of most
concern is pivoting strong upper jet streak through the wrn OH
valley this aftn atop tightly packed low level frontal slope. This
is turn likely to manifest a period of mesobanded snow especially
with added component of lower static stability arising within
impinging dryslot suggesting some convective snow bursts/greater
snowfall rates likely 16-00Z sw-ne. However highres guidance
signaling neither consistent or very agreeable on placement of
highest duration overlap. Loose consensus suggests areas within or
near a Monticello-Warsaw-Hillsdale line stand the best chance of as
much as 3-4" snow amounts, while a general 1-2 fits elsewhere. This
begs the question of whether an advisory is needed. Metro pavement
model indicates melting snow this aftn and without 1/2"/hr or
greater snowfall rates little if any impacts expected contrasted
with likely mesobanding and rates pushing 1"/hr for a time which
would present problems. Given the vagaries of highres model suite so
far and aftn timing best course of action is to punt to dayshift in
the hope that better model based delineation of highest snowfall and
associated impacts resolves with later runs.

Otherwise midlevel dryslot overspreads most of the area tonight with
some freezing drizzle possible mainly far south late.


.LONG TERM...(Monday through Saturday)
Issued at 243 AM EST Sun Feb 17 2019

Sfc ridging sprawls east through across the lakes through Tue ahead
of next upstream swrn US placed sw disturbance ejecting out and
shearing through the upper midwest late Wed. This will undoubtedly
reactive old stalled frontal zone through the TN/lwr MS valley as
forcing with upper wave passes well west. Blended pops still look a
bit overdone esp late Wed but generally accepted. Still appears as a
start with snow initially Tue night followed by a change over to
rain Wed morning.

Thereafter focus lies with more formidable parent low ejection next
weekend. GEM/EC similar in kind sfc and aloft with explosive
deepening through the wrn lakes versus a comparatively tame yet
vastly differing GFS solution. Soon to be operational GFS-FV3 though
does attempt to mimic the GEM/EC construct but 10mb weaker with sfc
cyclone. Nevertheless next weekend period remains of great interest
especially in the context of the idea that the ern US finally sees a
phased nrn/srn stream system.


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1222 PM EST Sun Feb 17 2019

Tricky forecast at the onset of the period. Hires models indicate
a mesoband forming shortly after start of period but exact
location is still uncertain. Accounted for possibility with a few
hour tempo further reducing visby over both TAF sites down into
IFR flight conditions. Otherwise light snow showers will continue
into the evening but should not impact visby too much. Fuel
alternate cigs remain through the end of the forecast period.





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