Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 250302

Area Forecast Discussion
National Weather Service Green Bay WI
1002 PM CDT Wed May 24 2017

Updated aviation portion for 06Z TAF issuance

Issued at 244 PM CDT Wed May 24 2017

The holiday weekend will start out mild with just some scattered
light precipitation, but likely end on a cooler and wetter note.

The blocky pattern over eastern North America will gradually
transition to a more consolidated northwest flow regime during the
period. As the upper low currently crosses the region shifts off
to the east, upper flow will briefly back to the southwest and
usher in some warmer and drier air. That won`t last long, as
another upper low will settle into the region during the weekend
and then linger into next week as ridging strengthens back
upstream along the West Coast.

Temperatures will start out cool, warm to near or a little above
normal for about the first half of the holiday weekend, then drop
back to below normal for the end of the weekend and next week.
There will be several opportunities for precipitation, with the
best chance occurring during the latter half of the holiday
weekend. Amounts are likely to end up near normal for the 7 day
period, which will be drier than the past couple weeks.

.SHORT TERM...Tonight and Thursday
Issued at 244 PM CDT Wed May 24 2017

The main short-term forecast issue is how long the extensive low
cloud deck will linger across the area. Satellite imagery does not
look very favorable for quick clearing after sunset as the more
cellular clouds are north and west of the area. Slowed the
decrease in clouds from the previous forecast, but further
adjustment in that direction may still be necessary. Also lingered
showers into the evening, mainly over the east.

The GFS and ECMWF generated a band of light precipitation over
eastern Wisconsin tomorrow afternoon. Though most of the rest of
the guidance is dry, have found that when those 2 models agree
they are often on to something. Added low PoPs to eastern
Wisconsin for tomorrow afternoon.

.LONG TERM...Thursday Night Through Wednesday
Issued at 244 PM CDT Wed May 24 2017

Unsettled pattern expected to continue into much of next week as
an upper trough remains across eastern North America with a ridge
across western North America. Northwest flow aloft will allow
disturbances to drop southeast into the western Great Lakes
from time to time.

First system expected to drop across the area late Thursday
night and Friday. Have the highest chances of rain north and
west of the Fox Valley with this feature. A few thunderstorms
are possible with this feature as well, but severe weather is
not expected. The chances of showers could linger into Friday
evening across the north.

More instability showers are expected on Saturday into Saturday
evening. Attention then turns to a more potent shortwave on
Sunday. Bufkit soundings indicated cape values of 300 to 500
j/kg, 700-500mb lapse rates around 6 C/KM, and total totals
around 50. Current thinking is there will be scattered
thunderstorms around the region late Sunday morning and Sunday
afternoon. Wetbulb zero heights around 7500 feet would support
the potential for some small hail. Some of the showers and storms
also could produce brief heavy rain and gusty winds. Scattered
showers may linger into Sunday night with another uptick in areal
coverage on Memorial Day due to daytime heating and another
shortwave approaching from the northwest. There may be a break
in the rain next Wednesday as weak ridging building into the
western Great Lakes. Temperatures Friday and Saturday will be
around normal, if not a little bit above. Temperatures for the
remainder of the period will be at or below normal.

.AVIATION...for 06Z TAF Issuance
Issued at 1002 PM CDT Wed May 24 2017

Moist cyclonic flow will continue to generate IFR to
a lower end MVFR cigs for most locations overnight into Thursday
morning. As the low pressure system departs east and a ridge of
high pressure builds into the region from the west, conditions
expected to improve to VFR levels Thursday afternoon through



SHORT TERM.....Skowronski
LONG TERM......Eckberg
AVIATION.......TDH is the U.S. government's official web portal to all federal, state and local government web resources and services.