Forecast Discussion for GRB NWS Office
831
FXUS63 KGRB 211142
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
642 AM CDT Sun Apr 21 2019

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Monday
Issued at 415 AM CDT Sun Apr 21 2019

Early this morning, regional radars indicated scattered showers
and a few storms across northern Minnesota and far northwest
Wisconsin, and another cluster of showers and storms across
south-central Minnesota. Temperatures early this morning were
in the upper 30s and 40s.

For today, the latest HRRR model wipes out the precipitation that
is currently across south-central Minnesota.However, there still
may be a shower or two across the north, thus continued small
chances this morning. Frontal boundary across far northern
Wisconsin will continue to sag slowly southward today. Some
question is where the front will be by 00z Monday, but should
still be just north of Green Bay. High temperatures tricky, as the
north may stay in the 50s while readings across central Wisconsin
may warm into the middle to upper 70s. The chances of showers and
storms will be on the increase later today, which is expected to
linger into Monday night. Per coordination with NWS Marquette,
issued a flood watch for Forest, Florence, Vilas and Oneida
Counties. Will issue an Hydrologic Outlook (ESF) for the remainder
of the area, although could see the rest of the forecast area
being places in a Flood Watch later today. For tonight, the far
north will be closer to the right entrance region of 300mb jet
which will aid lift and produce heavier precipitation totals
tonight into Monday morning.

For tonight, rain will continue across the far north in the west
to east axis. The rain may not make it to Wausau until closer to
12z and across northeast Wisconsin after 12z. Low temperatures
tonight will fall into the upper 30s far north to around 50 south.

For Monday, the real question is where the front will be.
Expecting the front will be around the Highway 29 corridor. North
of the front, temperatures will remain in the 40s to around 50,
while our southern tier counties will warm into the 60s to around
70. This is assuming the front does not sag further south then
expected. Precipitation amounts across central and east-central
Wisconsin may need to be bumped up over the next day as convection
may bring locally heavy rain along the boundary. Will also add
some patchy fog in the forecast. Scattered thunderstorms are
expected on Monday, but severe weather is not expected.

.LONG TERM...Monday Night Through Saturday
Issued at 415 AM CDT Sun Apr 21 2019

The main concerns for this forecast period are the precipitation
amounts from Monday night through Tuesday morning, and the
associated flooding impacts.

At the start of the forecast period, a surface cold front,
associated with showers and scattered thunderstorms, will be
bisecting the forecast area from central to far northeast WI. In
addition to this cold front, a surface low pressure system, will
position itself over central Wisconsin before tracking along the
frontal boundary. This low pressure system will bring additional
widespread QPF, between 0.25 inches and 0.75 inches, across the
forecast area, mainly through 15z Tuesday. The chances for
thunderstorms will mainly be focused across central and east-
central Wisconsin, which could locally boost rainfall totals. See
the Hydrology section below for information on potential flooding
concerns.

A surface high pressure system will begin moving over the
forecast area Tuesday afternoon and continue to prevail through
Wednesday.

An upper-level shortwave will sweep across northern Wisconsin on
Thursday, bringing the potential for more showers and possibly a
few thunderstorms.

Another surface high pressure system will push over Wisconsin on
Friday allowing dry conditions to return before an approaching
low pressure system brings the next chance for precipitation this
weekend.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 633 AM CDT Sun Apr 21 2019

For today, there may be a few showers this morning across the
north. Otherwise, a cold front across far northern Wisconsin
will gradually sink southward today. The cold front will help
trigger showers and a few isolated thunderstorms across the
north this afternoon. Occasional rain is expected by mid to
late evening (03z-06z) and continue into Monday at KRHI.
However, the rain may not make to KAUW/KCWA until around 11z
and Green Bay after 15z at the earliest. VFR conditions
should give way to MVFR/IFR CIGS across the north tonight
and across the remainder of the on Monday. Timing of the
low clouds questionable at KGRB/KATW/KMTW depending on
the frontal position. Showers and storms expected Monday
afternoon into Monday night.

&&

.HYDROLOGY...
Issued at 415 AM CDT Sun Apr 21 2019

Minor flooding continues on several rivers across the area. Look
for the the Wisconsin River to slowly fall early this week, while
the Wolf and Menominee rivers remain steady or are forecast to
slowly rise. Much of the region should see three quarters of an
inch to one and a half inches of rain from Sunday afternoon
through early Tuesday, with locally higher amounts possible,
especially in thunderstorms. The heaviest rainfall is expected
over north-central WI. Additional/new flooding concerns could
arise throughout the work week.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Flood Watch from this evening through Tuesday afternoon for
WIZ005-010>012.
&&

$$

SHORT TERM.....Eckberg
LONG TERM......Hykin
AVIATION.......Eckberg
HYDROLOGY......Hykin

NWS GRB Office Area Forecast Discussion