Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 252309

Area Forecast Discussion
National Weather Service Green Bay WI
609 PM CDT Sun Jun 25 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 312 PM CDT Sun Jun 25 2017

The precipitation trend from the 12Z models includes an increasing
chance for showers and some thunderstorms late this afternoon
before rain chances decrease during the night. Most locations will
still have a chance for showers through Monday and thunder is
possible Monday afternoon. The rain chances continue across much
of the forecast area since surface flow remains cyclonic, there is
a weak east-west surface boundary across Wisconsin and a 500 mb
low is forecast to pass across far northern Wisconsin.

Temperatures are expected to be below normal overnight but it
should not get too cold with clouds in place and dew points mainly
in the upper 40s and lower 50s. The clouds and showers, along with
continuing cold advection through Monday will keep highs around 15
degrees colder than normal. The 12Z NAM MOS only had a high of 57
at Green Bay and its 3-hourly temperatures decreased from 15Z
through 21Z before increasing a couple of degrees by 00Z Tuesday.
This seems unlikely, even with clouds and precipitation, since we
are less than a week past the summer solstice.

.LONG TERM...Monday Night Through Sunday
Issued at 312 PM CDT Sun Jun 25 2017

During early part of this period, the transition to a flatter,
zonal flow is complete. A couple of shortwave trofs will move
across the region and bring a couple periods of active weather.

Temperatures, for the most part, will remain at or below normal
into next weekend.

Dry weather on Tuesday is fleeting as surface ridge moves east,
allowing for return flow WAA to increase into state. The next
shortwave trof and surface reflection are forecast to move from
the northern Plains toward the Upper MS Valley by Wednesday AM.
Showers are likely Wednesday, along with scattered thunderstorms
as system moves into western Great Lakes and the trailing cold
front/occlusion reaches the WI/MN border late in the day.
Instability appears marginal and shear insufficient to
compensate, so widespread severe risk across northeast WI looks

The front is forecast to become stationary over southern WI or
northern IL on Thursday. Potential wave of low pressure could
ride along the front and enhance precip chances again late
Thursday night into Friday. Some significant differences between
GFS and ECMWF on this aspect of the forecast, so model blend will
suffice this far out.

.AVIATION...for 00Z TAF Issuance
Issued at 609 PM CDT Sun Jun 25 2017

Ceilings early this evening ranged from a lower end
VFR over east central wisconsin to MVFR levels over parts of
central and north central Wisconsin. Little to change overnight
into Monday as the region will remain in a moist cyclonic flow.
Bands of showers with isolated storms will continue to move east
central and far northeast Wisconsin this evening, then taper off
to isolated showers overnight. More showers are expected Monday as
the upper trough and cyclonic flow will linger one more day.



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