Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 161805

Area Forecast Discussion
National Weather Service Northern Indiana
205 PM EDT Mon Apr 16 2018

Issued at 200 PM EDT Mon Apr 16 2018

Scattered snow showers, possibly mixed with rain, are expected to
continue into tonight as a cold upper level system moves through
the region. Cool temperatures will continue tonight dropping back
into the 20s, but will be able to warm upper 30s to mid 40s
Tuesday. A warming trend takes hold into midweek when we have
another chance for rain.


.SHORT TERM...(This Evening through Tuesday)
Issued at 200 PM EDT Mon Apr 16 2018

Water vapor imagery depicting closed upper low over the area this
afternoon with a series of impulses rotating down the backside along
lake Michigan generating numerous snow showers over the forecast
area. Closed low will continue E/NE tonight but great lakes region
will still be under deep cyclonic flow and keep lingering chances
for snow showers over much of the area. Windy conditions this
afternoon will continue tonight in presence of strong surface
gradient. Low level thermal trof rotating down will aid in favorable
low level temperature profile to continue mixing down 25-30kt gusts
as well. Cyclonic flow finally lifts out of the area Tuesday
afternoon as weak surface ridging builds in from the west. Continued
unseasonably cold Tuesday with temps 20F below normal over most of
the area...clearing skies in SW CWA will allow for some moderation
into the low 40s while rest of the area only upper 30s to around


.LONG TERM...(Tuesday Night through Monday)
Issued at 200 PM EDT Mon Apr 16 2018

Weak surface ridging will provide a dry start to the forecast
period. Good radiational cooling for Tuesday night with mainly
clear skies and light winds...but strong low level thermal
response in advance of next system will temper cooling to 25-30F
for lows...but still 10-15F below normal. Pacific energy coming
onshore in the western US Monday will have longwave upper trof
axis shift from the west coast into the Rockies/high plains and
lead to closed low developing in the base of the trof. Surface low
associated with this system will lift out of the plains and track
northeast into the southern great lakes Wednesday. Despite strong
dynamics...moisture will be lacking as surface high pressure
remains anchored over the gulf of Mexico and effectively blocking
gulf return flow. Models remaining consistent in reflecting light
QPF amounts as a result. Decent WAA ahead of this system will have
temps near 60F in the southern CWA but track of surface low will
limit temps in the north to only around 50F. Lingering precip
chances Wednesday night into Thursday morning will have thermal
profiles supportive of possible mix with snow before ending.
Models trending toward an extended period of dry weather remainder
of the long term period. Next system coming onshore expected to
close off over the four corners region and become detached from
prevailing northern stream flow. This will keep it on a more
southerly track and allow Canadian high pressure to settle in over
the northern great lakes region and provide our area with a cool
but dry easterly flow. Temperatures will be seasonably cool in the
mid to upper 50s going into the weekend. Northern stream wave
coming into the Pacific northwest Saturday will induce downstream
ridging and height rises that will push eastward toward our area
and bring temps back to normal by the end of the forecast period.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 136 PM EDT Mon Apr 16 2018

An upper level low pressure system overhead slowly pushes off to
the east during the day today, but not before allowing for low
clouds, scattered drizzle and light snow showers. Within the
stronger snow showers, as low as IFR visibility is possible
especially closer to SBN as lake enhancement and diurnally forced
instability augment their intensity. With an enhanced pressure
gradient and diurnal forcing, gusty winds will continue into the
evening tonight, relaxing some overnight, but then picking up
tomorrow within the temperature gradient and diurnal forcing.
Overnight, expect low MVFR CIGs to moderate towards higher MVFR


LM...Small Craft Advisory until 5 PM EDT Tuesday for LMZ043-046.




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