Area Forecast Discussion
Issued by NWS Green Bay, WI

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346
FXUS63 KGRB 010002
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
702 PM CDT Sun Apr 30 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 315 PM CDT Sun Apr 30 2017

A strong mid level cyclone and surface low pressure system will
move from the southern Plains to Wisconsin by the end of the day
on Monday. As these features approach the state they will bring
showers, and possibly some thunderstorms, to the forecast area
tonight through Monday.

Light rain and drizzle that fell earlier in the day departed but
radar showed more rain upstream. Unlike Saturday, dew point
depressions in the southern part of the area were generally just a
few degrees at 19Z, and the 12Z GRB sounding was saturated up to
at least 600 mb. Locations farther to the north had temperatures
near 50 degrees with mid to upper 20s dew points, so it will take
a little longer to get any rain there. The rain should move in
from the south, ahead of the approaching mid level dry slot.
Models indicated enough elevated instability to go with a mention
of thunder as the band of rain to the south moves across the
area. After this band passes, rain should become more scattered,
but there will still be showers around through at least Monday.

.LONG TERM...Monday Night Through Sunday
Issued at 315 PM CDT Sun Apr 30 2017

Precipitation chances will slowly go down Monday night and Tuesday
as a low pressure system exits the western Great Lakes region.
Although the heaviest rain will be over by this period, rivers
could still rise as rainfall makes its way through the river
basins. The best precipitation chances will generally be across
the north where wrap around moisture continues to bring a feed of
moisture and mid level PV anomalies across the northwestern Great
Lakes. As colder air wraps into the system Monday night, snow will
mix in with the rain and even change over to all snow at times,
especially across north-central Wisconsin. However, given surface
temperatures are expected to be right around freezing and the
saturated soil from recent rains, snowfall amounts Monday night
and Tuesday morning are expected to be minimal, on the order of a
few tenths of an inch. Further west, across central Wisconsin,
some snow may mix in at times but a full changeover is not
anticipated.

Dry weather will finally make its way into the region Tuesday
night and Wednesday as high pressure builds in across the western
Great Lakes. Clearing skies and light winds should allow
temperatures Tuesday night to fall a few degrees below SuperBlend
values across north-central Wisconsin, closer to MOS guidance.

A weak low pressure system will bring a renewed chance for
precipitation late Wednesday night into Thursday. However the weak
nature of this low and limited moisture available will keep these
chances fairly low as this system traverses the western Great
Lakes region. The rest of the extended period, from Friday through
next weekend, appears to be fairly dry as the area resides on the
edge of a trough across the eastern Great Lakes and a ridge across
the Great Plains. The one exception appears to be Friday night
when a weak cold front tracks through the area.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 702 PM CDT Sun Apr 30 2017

Low pressure moving northeast from the southern Plains
will bring mainly IFR conditions and periods of rain through
Monday night. There could be a few thunderstorms tonight,
especially south of a Merrill to Door County line.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....MG
LONG TERM......Kurimski
AVIATION.......RDM



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