Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 150344

Area Forecast Discussion
National Weather Service Green Bay WI
1044 PM CDT Thu Sep 14 2017

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Friday
Issued at 214 PM CDT Thu Sep 14 2017

Due to a little more mixing, fog along the Lake Michigan shore
has finally lifted to a stratus deck, moved to the open waters or
diminished a bit. Forecast challenge for tonight then focuses on
low temps and fog potential again. Shower and storm potential
over Northwest Wisconsin is on the increase through Friday.

With a bit more mixing expected with the increasing south gradient
tonight into Friday, anticipate less fog in terms of coverage and
duration. But still anticipate some fog development in the rivers
basin areas and low lying areas. Fog has been persistent over Lake
Michigan the last few nights as well and patchy fog is possible
again overnight.

Post frontal scattered storms and showers were developing over
far Northwest Minnesota into North Dakota. The Convection was
also in a better sheared region with slightly higher PWATs. The
GFS and ECMWF were more aggressive with convection reaching the
DLH area by 4 pm this afternoon vs the drier NAM model. Due to
initialization, will run with the drier NAM tonight into Friday
and begin to bring in chances for convection Friday afternoon
across far North Central Wisconsin. The HRRR was also dry this
afternoon into tonight for far NW Wisconsin. Mid level lapse
rates are on the increase over Minnesota and far Northwest
wisconsin this afternoon, but plenty of dry air to overcome per
MSP raob this morning.

.LONG TERM...Friday Night Through Thursday
Issued at 214 PM CDT Thu Sep 14 2017

At the start of the period a few models continue to show a brief
opportunity for showers and perhaps some thunder in the far north
Friday evening. However, latest runs are trending towards keeping
the pcpn just north of Wisconsin. Kept slight chance mention in
far north- central Wisconsin, mainly Vilas and northern Oneida and
Forest Counties. Otherwise, the rest of the area to remain dry
Friday evening through Saturday afternoon.

A mid-level short wave begins pushing the surface cold front
southeast Saturday evening through Sunday afternoon. As the front
progresses expect to see the chance for showers and thunderstorms
move from NW to SE across the forecast area. Severe potential
appears minimal at this point. Stronger storm development looks
more likely to the west Saturday afternoon and evening when
instability will be greater. Weakening instability into the night
would suggest limited severe potential.

GFS, ECMWF, and Canadian still trying to come to a consensus on
the large scale pattern heading into next week. There seems to be
better agreement that surface high pressure and weak mid- level
ridging will keep the forecast area dry on Monday. Beyond that
differences persist. EC is still deepening the trough across the
western CONUS which allows a ridge to build across the western
Great Lakes region through the week. The GFS solution depicts a
broader trough in the west and the ridge developing much further
east, which puts us in a southwest flow pattern with opportunities
for multiple shortwaves to bring chances for showers and
thunderstorms. The Canadian is somewhere in between. Forecast
continues to features on/off chances for showers and thunderstorms
from Tuesday and beyond. It`s too early to determine if severe
storms would be a consideration at this point.

Temperatures will be well above normal on Saturday, cool off some
Sunday/Monday following the cold front (but still above normal),
and then return to highs in the low to middle 70s for the middle
of the week. Expect cooler highs along Lake Michigan most days.

.AVIATION...for 06Z TAF Issuance
Issued at 1037 PM CDT Thu Sep 14 2017

A few thunderstorms have developed over northwest Wisconsin this
evening. The airmass is considerably more stable over north-
central WI, so they may diminish before reaching Rhinelander. But
added a vcsh for a couple hours after midnight in case a shower
survives the trip. Otherwise, not expecting fog to be much of an
issue tonight, except for near the lakeshore possibly. Mainly
quiet weather for Friday into Friday night, with breezy south




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