Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 260836
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
336 AM CDT Mon Jun 26 2017

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 335 AM CDT Mon Jun 26 2017

A cold upper low will move across the region today and bring
clouds, showers and temperatures around 15 degrees below normal.
The air is cold enough for enhancement of the showers by the lake
and bay, so the best chance of rain is in those areas. Wet bulb
zero heights are very low, but instability is weak, so some very
small hail is possible. The showers should end from north to south
during the afternoon as the upper low departs.

Skies should clear tonight, and with a cool start to the evening,
lows should fall into the 40s in most locations, with some upper
30s in far northcentral Wisconsin.

Sunny skies and pleasant temperatures expected Tuesday, with
highs in the 70s.

.LONG TERM...Tuesday Night Through Sunday
Issued at 335 AM CDT Mon Jun 26 2017

The mean flow to have already de-amplified by the start of the
extended forecast, however this may only be temporary as models
indicate two separate shortwave troughs which will move through WI
Wednesday/Thursday and Friday/Saturday. The first system will have
a surface low/cold front accompany the trough with showers/
thunderstorms affecting northeast WI mainly Wednesday afternoon/
night. The second system appears more robust and will impact
northeast WI in two waves, Friday and again on Saturday. Bottom
line, look for unsettled weather to return with below normal
temperatures to end the month of June.

As the surface high shifts east into the Appalachians Tuesday
night, a return flow with WAA will increase across WI. Meanwhile,
a shortwave trough/cold front combination will be pushing across
the northern/central Plains. Increasing moisture transport should
bring a gradual increase in clouds across northeast WI mainly
after midnight and cannot rule out a stray shower from reaching
central WI toward daybreak. Temperatures will not get nearly as
cool as Monday night with readings for Tuesday night in the upper
40s to lower 50s north, mainly middle 50s south.

The shortwave trough/cold front reach the Upper MS Valley on
Wednesday with showers/thunderstorms spreading eastward across WI
through the day. Instability is initially lacking with MUCAPES not
getting above 500 J/KG until 00z Thursday. There will be plenty of
moisture available as the system approaches with PW values
climbing over 1.5 inches and dew points reach the lower 60s by
Wednesday afternoon. Some locally heavy rainfall is possible over
northeast WI later on Wednesday afternoon and with soil conditions
still somewhat saturated, there could be some areal flooding
possible. Max temperatures are expected to be near 70 degrees
north-central WI, lower to middle 70s elsewhere.

The potential for heavy rain will continue into at least Wednesday
evening as the shortwave trough/cold front move into the western
Great Lakes. Severe risk should be held to a minimum due to all
the clouds/precipitation in the area, even as MUCAPES get into the
500-1000 J/KG range. The main concern would be possible flooding
or river flooding Wednesday night as saturated soils would
continue and some rivers are still running high/fast flows. This
will need to be watched over the next 36-48 hours. Showers and
thunderstorms should start to diminish later Wednesday night as
the better lift/mid-level forcing shift east into Lower MI. Min
temperatures to range from the middle to upper 50s north-central,
lower to middle 60s east-central WI. Lingering light showers/
perhaps a stray thunderstorm to carry over into Thursday morning,
however most of Thursday appears to be dry as the area to reside
between systems. If we can get even a little sunshine,
temperatures would be able to warm up a bit. For now, have max
temperatures in the lower 70s north-central, generally 75-80
degree range elsewhere.

After a quiet Thursday night, precipitation chances look to be on
the increase again as the next shortwave trough/cold front
push into the western Great Lakes on Friday. The higher pops are
expected to be over the southern half of WI where the models show
a surface wave moving northeast along the cold front. Since
northeast WI never truly gets into the warm sector, the threat for
any severe storms appears to be minimal at this time. Max
temperatures for Friday will be cool once again with the
increasing chance for precipitation, thus readings will only be
around 70 degrees north-central/lakeshore, lower to middle 70s
elsewhere.

Precipitation trends are forecast to gradually diminish Friday
night as the shortwave trough moves east, along with the surface
wave/cold front. However, cannot rule out a small chance of
showers on Saturday as the next shortwave trough sweeps into the
Upper MS Valley and mid-level forcing begins to increase over WI.
Max temperatures on Saturday will remain cool with readings
similar to Friday. This latest shortwave trough quickly moves
across WI Saturday night and be to our east on Sunday. Will keep a
small pop for Saturday night with the passage of the trough, then
mainly dry conditions are expected on Sunday as weak high pressure
moves into the region.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1113 PM CDT Sun Jun 25 2017

Ceilings late sunday evening were mainly vfr with patchy mid
level clouds. The only exception is the far north and northeast
where area of mvfr cigs were noted along with isolated light
showers. Little to change overnight into Monday as the region will
remain in a moist cyclonic flow. More showers are expected Monday
as the upper trough and cyclonic flow will linger one more day.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......Kallas
AVIATION.......TDH



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