Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 232338
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
638 PM CDT Wed May 23 2018

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Thursday
Issued at 331 PM CDT Wed May 23 2018

Daytime cumulus clouds developed across much of the area late this
morning and afternoon, with the most coverage over northern WI
where the fewest high clouds were located and surface temps
climbed into the lower to middle 80s. The thicker high clouds
held down temps slightly which keep the daytime cumulus clouds in
check.

A dry evening is expected across the area, with the daytime
cumulus clouds fading away, but the higher clouds will continue to
drift across the region. Chance for showers and possibly a storm
arrive across central and northern WI later tonight into Thursday
morning as the upper level ridge slides to the east and moisture
increases as the low-level jet points into western WI and MN. Best
forcing and moisture stays to our west, so will confine POPs to
central and north central WI. Very limited instability, so no
severe weather is expected. It will be warmer night across the
area, especially over the north, with highs mainly in the middle
50s to around 60 (cooler near Lake MI).

Any overnight activity should weaken toward sunrise as the low-
level jet weakens, but additional showers and storms will be
possible through the day as models show instability building,
highest across central and north central WI, with CAPEs in the
1-2K J/KG range. Bulk shear values will be weak, generally under
20 kts, and no surface feature really to focus any organized
convection on, so while a few strong storms are possible, severe
weather is looking unlikely. Will keep POPs on the low side,
highest across central and north central WI, with eastern WI
staying dry. 850/925mb temps climb a couple degrees by Thursday
afternoon, so for most locations will be slightly warmer than
today. Dewpoints hovering in the upper 50s to lower 60s will make
for a summer-like day.

.LONG TERM...Thursday Night Through Wednesday
Issued at 331 PM CDT Wed May 23 2018

Thunderstorm chances are the main concern in the long term.

Instability ahead of an approaching mid level trough, and a
frontal boundary associated with a surface low moving across
southern Canada, will bring a chance for showers to central and
north central Wisconsin Thursday night. Rain chances increase and
spread across the rest of the area on Friday and thunderstorms
can also be expected. The showers and storms should persist
through at least the evening before winding down late Friday
night/Saturday. Severe storms can`t be ruled out, but shear is
not that strong and SPC only has a marginal risk of severe storms
for 12Z Friday through 12Z Saturday. Not really anything more than
slight chance PoPs for the rest of the weekend through the middle
of next week with surface high pressure and a mid level ridge the
main features in the region.

Expect warmer than normal temperatures, with lows in the 50s and
60s. Highs should be in the 70s and 80s, but it will be cooler
near Lake Michigan.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 636 PM CDT Wed May 23 2018

Good flying weather expected tonight and Thursday, with just a
very small chance of a shower or thunderstorm late tonight and
Thursday across central and northcentral Wisconsin. There is also
a chance of some low clouds along the lake Michigan shoreline late
tonight and early Thursday.

&&

.MARINE...
Issued at 331 PM CDT Wed May 23 2018

Moist air flowing over the cool waters of Lake Michigan will
continue to produce areas of dense fog. Not much change in
dewpoints or wind direction into Thursday, so fog is likely to
continue.
&&

.FIRE WEATHER...
Issued at 331 PM CDT Wed May 23 2018

Low RH values will continue this afternoon and evening across
northern and far northeast WI. An increase in moisture and shower
and thunderstorm chances are forecast for the end of the week
which could provide much needed relief from the dry conditions and
ease the fire weather threat.
&&

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

$$

SHORT TERM.....Bersch
LONG TERM......MG
AVIATION.......RDM
MARINE.........Bersch
FIRE WEATHER...Bersch



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