Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 271938
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
238 PM CDT Sun May 27 2018

Forecast discussion for routine afternoon forecast issuance

.SYNOPSIS...
Issued at 238 PM CDT Sun May 27 2018

Still very warm and rather humid on Memorial Day (though not as
hot as today), then temperatures gradually edging back closer to
seasonal normals.

On the large scale, a broad, strong, and relatively low amplitude
band of westerlies was located across Canada and the adjacent
oceans. A weaker high-amplitude branch of the flow was across the
CONUS, with a deep trough/closed low over the West, a sharp ridge
over the eastern Plains, and a broad/diffuse trough over the
East. Energy peeling out of the northern stream and digging down
the West Coast will kick the current western U.S. trough eastward
by mid-week. It will weaken as it lifts out and flattens the
downstream ridge, eventually merging with the remnants of
subtropical storm "Alberto" over the eastern Great Lakes region
and Ontario by late in the week. By next weekend, a broad and
fairly strong band of westerlies is forecast to be across southern
Canada and much of the CONUS. The will be a broad trough across
the West and ridging over the Great Lakes region before the flow
splits into a ridge-"over"-trough pattern over eastern North
America.

Very warm air is in place across the area. After record/near
record temperatures today readings will edge back somewhat. But
they should remain considerably above normal through at least
Thursday, though they could be held back a little by thunderstorm
outflow and east winds at times. Temperatures will return closer
to normal for the upcoming weekend. There will be at least a few
opportunities for rain, with the best occurring during the
Wednesday-Thursday time frame when the remnants of "Alberto"
and the remnants of the western U.S. upper trough cross the region.
Since it appears the primary surge of tropical moisture with
"Alberto" will pass east of the area, rainfall totals will depend
on where the scattered showers and thunderstorms develop, and may
vary considerably from place to place.
&&

.SHORT TERM...Tonight and Monday
Issued at 238 PM CDT Sun May 27 2018

See climate section of the area forecast discussion on the
record setting temperatures this afternoon. Temperatures
this afternoon ranged from the middle 80s across the far
north with 90s over much of the rest of the region. The
exception was across eastern Wisconsin where well distinct
lake/bay breeze boundaries were spreading westward. At last
check, it was 61 degrees at Northport Pier and 68 at the
Kewaunee shoreline. In comparison, the buoy on the northern
end of Lake Michigan was 41 degrees with a water temperature
of 38 degrees.

For the rest of the afternoon into the eastern, lake/bay
breeze boundaries continue to push westward. Bufkit soundings
and meso models would suggest we stay dry despite these well
distinct boundaries. Will continue the dry forecast for this
evening. Later tonight, a cluster of showers and thunderstorms
is expected to move across far northern Wisconsin by daybreak.
Have chances of showers and storms to cover this feature. Still
some uncertainty in the coverage of precipitation, thus kept it
in the chance category for now. Any showers and storms are
expected to dissipate by mid to late morning.

The showers and thunderstorms could produce an outflow boundary
that could push southward across the northern half of Wisconsin.
There are differing solutions on how far south this boundary
would make it. Took a compromise between the northern/southern
solutions. This will make for a possible larger temperature
gradient across the forecast area. Lowered high temperatures
across the north and far northeast due to the potential for
the outflow boundary and cloud cover during the morning.

Things get interesting during the afternoon hours on Memorial
Day. The combination of the heat and more humidity, combined with
a boundary across the area will bring a chance of thunderstorms
during the afternoon hours. If storms form, they are expected to
become strong or severe with damaging winds and large hail along
with torrential rainfall. Stay tuned!.

.LONG TERM...Monday Night Through Sunday
Issued at 238 PM CDT Sun May 27 2018

Though its exact position at the start of the long-term portion of
the forecast will depend on earlier convection and is difficult to
determine, a weak frontal boundary is likely to be somewhere
across the area at 00Z Tuesday. It should slide should south and
west across the remainder of the area during the evening. Although
large scale forcing will be weak as the forecast area will be near
center of a broad mid-upper level anticyclone, low-level
convergence near the boundary could result in some some
convection. Given the expected instability, isolated strong wind
gusts and brief heavy rains will be possible with the storms.

There will be a lull in the precip chances until Wednesday into
Thursday when weakening energy that ejected out of the western
trough reaches the area while the remnants of Alberto are lifting
toward the central Great Lakes region. It still looks like the
main surge of the tropical moisture will be shunted just east of
the area, but forcing and moisture should still be sufficient for
scattered to numerous showers and storms.

Another cold front will drop through the area Friday. Cooler and
drier conditions should set up over the area for at least a couple
days in the wake of the front, as the forecast area remains on
the southwest flank of a large sprawling Canadian anticyclone
settling into the Hudson Bay region. The dry air may still allow
afternoon temperatures to warm to AOA normal (except near the lake
and bay), but overnight lows will probably drop to AOB normal. The
medium range models suggest precipitation chances could return by
the latter part of next weekend, though would not be surprised if
those eventually need to be delayed given the upper pattern.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1150 AM CDT Sun May 27 2018

VFR conditions will continue this afternoon into much of
tonight. Some patchy fog is possible after midnight across
the far north. The other concern will be the chances of showers
and storms late tonight. Some showers and storms will move
across north-central late tonight into Memorial Day morning.
For the remainder of Memorial Day, there is low confidence
in the wind forecast as a weak boundary drops southward into
the area. If there is more widespread convection across
northern Wisconsin during the morning, front may be pushed
southward than what some of the models are indicating. However,
the models are not in agreement with how much convection will
be around. Some adjustments in the wind forecast is likely
along with the chances of storms on Memorial Day, especially
during the afternoon hours.
&&

.CLIMATE...
Issued at 238 PM CDT Sun May 27 2018

The temperature this afternoon at Green Bay warmed to 96 degrees,
making it the 2nd warmest temperature on record during the month
of May. The warmest temperature was 99 degrees on May 31, 1934
(dust bowl years). As of 2 pm, these sites have set record high
temperatures for today: Rhinelander at 92 degrees, Marshfield at
91 degrees, Wisconsin Rapids at 95 degrees, Oshkosh at 91 degrees
and Wausau at 91 degrees. A record event report will be sent out
later this afternoon. More record highs are possible across
central and portions of northeast Wisconsin on Memorial Day.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Eckberg
LONG TERM......Skowronski
AVIATION.......Eckberg
CLIMATE........Eckberg



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