Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 041006

Area Forecast Discussion
National Weather Service Northern Indiana
506 AM EST Sun Dec 4 2016

Issued at 505 AM EST Sun Dec 4 2016

An area of snow mixed with rain will move through the region
today. Precipitation should fall as mainly snow north of a line
from Monticello to Fort Wayne to Lima with 2 to 4 inches over
northwest Indiana into far southern Lower Michigan. More wet snow
is likely Tuesday before much colder air and lake effect snow
arrive late this week.


.SHORT TERM...(Today and Tonight)
Issued at 447 AM EST Sun Dec 4 2016

An upper level trof will move east today and bring a round of
precipitation to the area. High resolution WPC models favor a
rather intense band of snow or a rain/snow mix for 3 to 6 hours
associated with this system. BUFKIT profiles favor snow over
northwest areas mainly northwest of Warsaw with generally a
rain/snow mix over southeast areas. The dendritic growth zone will
also be favorable for snow development given impressive omega
through this layer. The 295K isentropic layer of the RAP also
supports a rather intense band of snow with 30-40 kts of lift with
3.0 to 4.0 g/kg of moisture. Therefore, have raised snow amounts
considerably especially over these northwest areas to around 3
inches. Current thinking is roads will be mainly wet given
pavement temps staying above freezing. The snow should end rather
quickly over all areas by early tonight.


.LONG TERM...(Monday through Saturday)
Issued at 447 AM EST Sun Dec 4 2016

...Wet snow Tuesday then much colder weather and lake effect snow
still on track for later this week...

A second system expected to arrive Tuesday will follow the path of
the system that moves across the area today. Favor more of a wet
snow forecast in lieu of a rain solution given the latest forecast
thermal profiles. This system will be an ejecting upper low from the
southern stream. Have trended this low and associated precipitation
farther northwest given solid support from the GFS and the ECMWF.

A third system will bring much colder air to the area late this
upcoming week. The ECMWF continues to be at odds with the GFS and
still holds onto the Wednesday night frontal wave, bringing a round
of snow ahead of a very strong cold front. There is also support
from other models for this wave. Have rejected the model blend
and kept the previous forecast given uncertainty. Lake effect snow
will develop Thursday as much colder air spreads over the mild
lake waters. Delta T values should eventually reach 25 to 30C, so
lake effect snow accumulations appear very favorable at this time.
A fourth system appears on the horizon with snow chances
increasing Saturday.


.AVIATION...(For the 06Z TAFS through 06Z Monday Morning)
Issued at 1249 AM EST Sun Dec 4 2016

Ewd ejection of broad central plains based sw trough focus this
period. Fairly broad arc of precip this morning from the central
plains sewd into the Tn valley within general zone of moist/warm
advection. Weak frontal wave over the lower MS valley will lift newd
into the ern OH valley by tonight as sw pivots into lower MI.
Primary concern is potential for burst of accumulating snow invof of
KSBN given adequately cold environmental thermal profile and
maximized zone of ascent that develops within zone of strong
isentropic lift. At least potential exists for a period of lifr
conds late aftn-early evening. Otherwise general deteriorating trend
to flight conditions expected to commence this aftn as upstream
precip shield advances ewd across the terminals.




SHORT TERM...Skipper
LONG TERM...Skipper

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