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Forecast Discussion for Green Bay, WI

FXUS63 KGRB 230455

Area Forecast Discussion
National Weather Service Green Bay WI
1155 PM CDT Thu Jun 22 2017

Updated aviation portion for 06Z TAF issuance
and new information added to update section

Issued at 1150 PM CDT Thu Jun 22 2017

The heaviest rains have finally shifted south of the area, but
light showers and a few thunderstorms are likely to linger over
east-central Wisconsin for a while overnight. Dense fog quickly
formed across the north mid-evening, but has dissipated a bit
now--probably due to some mid-clouds moving back over that area
and some mixing as winds above the surface increase due to the
arrival of the tail of a mid-level shortwave. The fog may thicken
again later tonight. At this point, plan to handle with and SPS
unless it become much more widespread.

.SHORT TERM...Tonight and Friday
Issued at 243 PM CDT Thu Jun 22 2017

Showers and scattered thunderstorms continued to move across the
region this afternoon. The clouds and rain have pretty much
diminished the chances of severe weather in our area. Still think
some of the stronger storms could produce gusty winds to around 40
mph and small hail south of a Marshfield to Green Bay to Algoma
line. The bigger story will be the locally heavy rain. So far
today, Marshfield has received 1.44 inches of rain with amounts
over 2 inches in Manitowoc.

For the rest of the afternoon, showers will continue across the
north and showers and scattered thunderstorms across the south.
The showers and storms will gradually end from northwest to
southeast this evening north and west of the Fox Valley, and
early Thursday morning from the Interstate 41 corridor east to
the lake.

On Friday, fair weather cumulus clouds will develop by mid to
late morning. Have added a small chance of instability showers
Friday afternoon over much of the area. Did not stray far guidance
for lows tonight and took a blend of the warmer mav and cooler
met guidance for highs on Friday.

.LONG TERM...Friday Night Through Thursday
Issued at 243 PM CDT Thu Jun 22 2017

Models in general agreement on the overall pattern through the
middle of next week, with differences arising in the timing and
location of smaller features. Attention in the long term will be
on timing of various mid- level shortwaves and the resulting pcpn
chances and temperatures.

Friday evening...Any lingering showers should quickly diminish as
daytime heating is lost and the shortwave energy slides
southeast. A dry period is expected Friday evening through
Saturday mid/late morning.

Saturday through Monday...An upper level trough remains firmly in
place across the Upper Midwest/western Great Lakes. This puts the
area in northwest flow and allows for multiple mid-level shortwaves
to stream through, with showers and afternoon thunderstorms in
the forecast each day. The best timing based on 12Z model runs is
from early afternoon through early evening Saturday, Sunday, and
Monday. Severe potential looks rather low as dew points fall into
the 40s/low 50s, MUCAPES top out anywhere from 400-1400 J/kg
depending on what model you reference, and bulk shear is only 10
to 20 knots Saturday and Sunday, and increases some on Monday.
Temperatures will be running as much as 10 to 15 degree below
normal, with highs only forecast to be in the low 60s in north-
central Wisconsin on Saturday and Sunday. Could see these
temperatures needing a slight boost if more sun/less showers

Tuesday...Models still show surface high pressure building into
the region. This will result in a welcomed dry day and warmer

Midweek...Models diverge here but all suggest transitioning to a
west/southwest flow which will lead to the return of seasonal
temperatures and moisture. It appears a surface frontal system
will brings more shower and thunderstorm chances in the Wednesday
and Thursday time frame, but exacting timing details are unclear
this far out. Will settle with a model blend.

.AVIATION...for 06Z TAF Issuance
Issued at 1150 PM CDT Thu Jun 22 2017

Though patchy dense fog will definitely be an aviation concern
overnight, the overall trend should be for improving conditions
the rest of the night. Fairly good flight conditions are expected
Friday, with gusty west winds probably the biggest concern.

Issued at 243 PM CDT Thu Jun 22 2017

An inch or two of rain has fallen at many locations south of a
Kewaunee to Wausau line. An additional inch of rain with locally
higher amounts are still possible for the remainder of the
afternoon and evening in this region. Many rivers will be on
the rise with abnormally high levels and fast flows for late
June. Please check for the latest river forecasts and warnings.



SHORT TERM.....Eckberg

NWS Green Bay, WI (GRB) Office Area Forecast Discussion

Discussion Script by Ken True at Saratoga Weather - WFO Script by SE Lincoln Weather