Forecast Discussion for GRB NWS Office
FXUS63 KGRB 162106

Area Forecast Discussion
National Weather Service Green Bay WI
406 PM CDT Tue Aug 16 2022

Forecast discussion for routine afternoon forecast issuance

Issued at 406 PM CDT Tue Aug 16 2022

Seasonable temperatures for the rest of the work week. The chance
for showers will gradually increase during the latter part of the
work week, then scattered showers and some thunderstorms are
expected for the weekend.

Amplification of the western ridge/eastern trough pattern is
expected the next few days as a series of shortwaves dig south
from Canada. The shortwave energy will eventually close off over
the Upper Midwest/Great Lakes region, temporarily pulling the
eastern trough axis back to the west for the weekend. The trough
should shift back east next week.

Rain chances will slowly increase from northwest to southeast
across the area during the latter part of the work week, then
scattered showers and thunderstorms are expected for the weekend.
Seven-day rainfall totals will probably range from near to a
little below normal in the eastern part of the area to above
normal in the west. Temperatures throughout the period probably
won`t stray too far from seasonal normals, running a little warmer
on days with more sunshine and a little cooler on days with more
clouds and precipitation.

.SHORT TERM...Tonight and Wednesday
Issued at 406 PM CDT Tue Aug 16 2022

Quiet weather will continue tonight as weak high pressure
continues to ridge into the area from Ontario. As stronger
shortwaves begin digging farther west toward the Northern Plains
tomorrow, the forecast area will temporarily become situated in a
col in the mid-level wind field between the energy to the west
and the main portion of the eastern NOAM longwave trough to the
east. This suggested slowing the arrival of rain chances a bit on
Wednesday. Trended the forecast in that direction, but some
further adjustment may still be necessary with subsequent
issuances. Edged temps across most of the above the NBM guidance
for tomorrow given current temps across the area and a bit of
anticipated warming at 850 mb. The exception will be the NW part
of the area which will have more clouds.

.LONG TERM...Wednesday Night Through Tuesday
Issued at 406 PM CDT Tue Aug 16 2022

The main focus from this forecast period revolves around
precipitation trends associated with a closed low. Temperatures will
be dependent on when and where the rain falls and cloud cover.

Wednesday night through Thursday...A weak mid-level shortwave over
Ontario will become nearly stationary during this time period.
Meanwhile, low to mid-level moisture associated with this shortwave
will extend into northwest WI. A few showers and thunderstorms may
reach north-central WI Wednesday night as a result. However, heading
into Thursday, a secondary (stronger) shortwave will dig over
eastern ND/northern MN. The two shortwaves will slowly combine on
Thursday over the Upper Mississippi Valley and bring shower and
thunderstorm chances to the forecast area, with the best chances
over central and north-central WI.

Rest of the extended...The shortwave will continue to strengthen
over MN and eventually become closed sometime Thursday night into
Friday. Models are in agreement with the low`s track dropping south
over MN on Friday, which will cause a mean south/southwest flow over
the forecast area. As the moisture continues to circulate around the
closed low, additional showers and isolated storms will remain
possible across the forecast area on Friday. Due to the slow
east/southeast progression of the closed low from southern MN to
southern WI, periods of showers and isolated thunderstorms will also
be possible throughout the remainder of the weekend and into early
next week. However, models do not suggest a complete wash-out for
the forecast area.

.AVIATION...for 18Z TAF Issuance
Issued at 1230 PM CDT Tue Aug 16 2022

Generally good aviation weather conditions are expected
throughout the TAF period. Diurnal Cu will continue to form this
afternoon, but bases will be VFR. Patchy fog is possible tonight.
There is a hint of it on the LAV guidance at KCWA and KGRB, so
will include with a TEMPO group at those sites for late tonight
since it doesn`t look like it will be very widespread/persistent.



SHORT TERM.....Skowronski
LONG TERM......Hykin

NWS GRB Office Area Forecast Discussion