Special Weather Statement, NWS Green Bay, WI

Area Forecast Discussion
National Weather Service Green Bay WI
327 PM CDT Sun Jun 4 2017

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Monday
Issued at 326 PM CDT Sun Jun 4 2017

Main forecast challenge to be on extent of precipitation late this
afternoon/evening as a cold front/strong shortwave trough drop
south through the region. There are still questions as to how
unstable northeast WI can get before any storms arrive as dew
points have dropped into the 40s and 50s.

The 19z MSAS surface analysis showed one area of low pressure over
east-central Lower MI with a cold front stretched southwest into
IL. The cold front of interest extends roughly from extreme
southeast Ontario westward through Upper MI, then northwest back
into southwest Ontario. The radar mosaic had seen an uptick in
showers and thunderstorms over northeast MN into central Upper MI.
Lastly, taking a look at the water vapor satellite imagery showed
an impressive shortwave trough draped across southern Ontario.

The cold front/shortwave trough combination will sweep south
through northeast WI this evening (a bit slower than advertised 24
hours ago) and bring a chance of showers/thunderstorms to the
area. Forcing and shear are more than sufficient for precipitation
development, however the later arrive time places concern on
instability and whether any of these storms could become severe.
Dew points do climb back into the 50s just ahead of the cold
front and SPC continues the marginal risk this evening, so cannot
rule out an isolated damaging wind event. As the cold front pushes
through the forecast area, look for winds to veer north-northeast
and become gusty, especially over eastern WI near the bay and
lake. Otherwise, an influx of CAA will bring low clouds back to
the region late tonight. Min temperatures will range from the
upper 40s to lower 50s north, lower to middle 50s near Lake MI and
middle to upper 50s south.

Lingering low-level moisture will keep these clouds around through
mid-morning before mixing a drier air advecting into WI allows for
skies to become mostly sunny by midday through the afternoon. High
pressure centered over Ontario is forecast to build south into the
western Great Lakes on Monday and will be our main weather feature
into mid-week. Max temperatures on Monday will be noticeably
cooler with readings in the upper 60s to lower 70s north/near Lake
MI, lower to middle 70s south.

.LONG TERM...Monday Night Through Sunday
Issued at 326 PM CDT Sun Jun 4 2017

High pressure will bring quiet dry weather to the western Great
Lakes through the middle part of the work week. Temperatures
during this period are expected to drop into the 70s for daytime
highs, with 40s and 50s expected for nighttime lows.

The next chance for rain will not occur until late in the week
when a weak low pressure system tracks through the western Great
Lakes region. There could be some thunder with any showers that
form, however instability will be rather weak. High pressure will
keep the first half of next weekend dry, however another weak low
pressure system could bring some showers next Sunday. There are
model discrepancies that far out, therefore there is a chance all
of next weekend could be dry.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1240 PM CDT Sun Jun 4 2017

Mainly VFR cumulus clouds this afternoon. The passage of a cold
front and mid-level trough of low pressure this evening will bring
a chance of showers/thunderstorms to the region, especially over
eastern WI. Any of the heavier showers or storms may allow vsbys
to drop briefly into the MVFR category. Winds are expected to
sharply veer north-northeast behind the cold front and become
gusty, especially at the GRB and MTW TAF sites. As cooler air
settles into the area overnight, a band of low clouds is forecast
to overspread much of northeast WI. Cigs could drop into the IFR
range roughly between 10z and 14z with localized LIFR conditions
possible. These clouds are expected to linger through at least the
mid-morning hours of Monday before drier air begins to advect into
WI and skies become mostly sunny. VFR conditions to then prevail
for Monday afternoon.
&&

.MARINE...
Issued at 326 PM CDT Sun Jun 4 2017

A strong cold front is forecast to move quickly south across the
area late this evening into the overnight hours. Winds will
abruptly shift from northwest to northeast behind the front and
increase in speed with gusts to 25 knots. As a result, waves are
expected to build to 2 to 4 feet. A small craft advisory remains
in effect from 9 PM this evening until 7 PM Monday.
&&

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

SHORT TERM.....Kallas
LONG TERM......Kurimski
AVIATION.......Kallas
MARINE.........Kallas

Hazardous Weather Outlook
National Weather Service Green Bay WI
250 PM CDT Sun Jun 4 2017

WIZ005-010>013-018>022-030-031-035>040-045-048>050-073-074-052000-
Vilas-Oneida-Forest-Florence-Northern Marinette County-Lincoln-
Langlade-Menominee-Northern Oconto County-Door-Marathon-Shawano-
Wood-Portage-Waupaca-Outagamie-Brown-Kewaunee-Waushara-Winnebago-
Calumet-Manitowoc-Southern Marinette County-
Southern Oconto County-
250 PM CDT Sun Jun 4 2017

This Hazardous Weather Outlook is for north-central and northeast
Wisconsin.

.DAY ONE...Tonight

Thunderstorms are possible over far northeast and parts of east-
central Wisconsin late this afternoon through the evening hours.
If enough moisture can return to the area, a few of the storms
could become severe and produce localized wind gusts to around 60
mph and hail to 1 inch in diameter. If severe weather occurs, it
would most likely be between 400 pm and 900 pm. Anyone with
outdoor plans late this afternoon into the evening should monitor
later forecasts for updated information on this marginal severe
weather risk.

.DAYS TWO THROUGH SEVEN...Monday through Sunday

There is a chance of thunderstorms Thursday into Friday. It is too
early to determine if any of the storms would become severe.

.SPOTTER INFORMATION STATEMENT...

Spotters late this afternoon and evening are requested to report
wind gusts over 40 mph and hail.

LMZ521-522-541>543-052000-
The Bay of Green Bay south of a line from Cedar River MI to Rock
Island Passage-Lake Michigan from Washington Island to Sheboygan-
250 PM CDT Sun Jun 4 2017

This Hazardous Weather Outlook is for portions of northwest Lake
Michigan and the waters of Green Bay.

.DAY ONE...Tonight

Thunderstorms are possible late this afternoon and this evening.
The storms could produce gusty winds and hail.

An abrupt wind shift to the northeast is likely to surge down the
lake and bay this evening. The exact timing and strength of the
winds associated with the wind shift remain uncertain, it will
likely pose a substantial hazard to small craft when it occurs.
Anyone boating on the lake or bay this evening should closely
monitor weather conditions and forecasts prior to heading out on
the water.

.DAYS TWO THROUGH SEVEN...Monday through Sunday

Northeast winds will result in hazardous boating conditions for
small craft on Monday.

There is a chance of thunderstorms Thursday afternoon into
Friday that may pose a hazard to mariners.

Kallas/Kurimski

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