Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 171117
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
617 AM CDT Mon Jun 17 2019

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 356 AM CDT Mon Jun 17 2019

Main concern in the short-term portion of the forecast will be
timing and placement of greatest chances of precipitation as several
shortwaves rotate through the north half of Wisconsin. Temperatures
will be closer to average for this time of year, which is in the mid
to upper 70s.

Today: A surface ridge is expected to remain over the area today,
while all of northern WI will be on the southern fringes of a 500mb
trough extending south and west from a 500mb closed low east of
Hudson Bay. This will allow for a brief break in the precipitation
and unsettled weather. High to mid clouds may linger across central
and east-central portions of Wisconsin, while increasing clouds can
be expected during the afternoon hours across the north-central. The
rest of the area will end up with clear to partly cloudy skies. A
weak surface trough and upper-level shortwave will approach from the
west late this afternoon. This could touch off a few showers and
possibly a thunderstorm across the north-central, but the better
chances will occur in the evening. High temperatures will be much
warmer for most locations today with highs expected to be in the 70s.

Tonight and Tuesday: The aforementioned surface trough is expected to
remain nearly stationary or shift slowly to the east through this
time period. For the most part, this will be the main focus of any
shower and thunderstorms. The shortwave is expected to
flatten/weaken as it slides across the area this evening, but it may
still allow for enough instability to touch off a few thunderstorms.
That shortwave will shift east of the area during the overnight
hours and dissipate, while the next shortwave approaches from the
west. This shortwave is progged to slide across the area, especially
across the north, by early Tuesday afternoon. Again, their will
likely be enough instability around with the shortwave to touch off
some scattered showers and thunderstorms.  At this point, have kept
scattered mention for pops as the better chances will need to be
focused with the boundary and waves as they approach/pass through
the area. As confidence increases with the timing, increased pops
will likely be necessary. Overnight lows will be mainly in the 50s
with daytime highs warming into the 70s again!.

.LONG TERM...Tuesday Night Through Sunday
Issued at 356 AM CDT Mon Jun 17 2019

Precipitation chances from Tuesday night through Friday are the
main concern as a fairly zonal flow aloft and model differences
make pinpointing timing difficult. A change in the mean flow will
likely bring a more active weather pattern next weekend, although
it is too early to determine if the storms would become severe.

For Tuesday night, left a small chance of showers through the
night. On Wednesday, mainly dry conditions are expected across the
north. Left a small chance of rain across the south with system
passing well south of the area. The GFS/NAM models would suggest
rain chances would be higher across the Fox Valley and lakeshore
region. On the other hand, the Canadian and ECMWF are dry, so the
forecast would be a compromise between the two different solutions.
Weak high pressure moves across the region on Thursday as the
next round of rain across the Dakotas and Minnesota moves towards
us during the day. Rain is possible late in the day across
portions of central and north-central Wisconsin.

The areas of showers should gradually dissipate as they move into
north-central and central due to dry air in place Thursday
afternoon and Thursday evening, which is represented by the
GFS/ECMWF solution. For Friday through Sunday, will trend toward
the ECMWF/Canadian solutions for precipitation chances. Based on
the model solution of the ECMWF/Canadian model, have concerns
about high temperatures Friday and Saturday due to cloud cover,
rain and cooler southeast flow off Lake Michigan. Temperatures may
need to be lowered over the next few days if these conditions
continue. No changes made to the Sunday forecast as this time.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 617 AM CDT Mon Jun 17 2019

A mid-level cloud deck continues to linger across central and
east-central portions of WI, impacting the southern TAF sites with
around 5-6kft ceilings. Conditions will improve through this
afternoon at all TAF sites with good flying conditions expected. An
approaching low/trough will cause clouds to increase across the
area late this afternoon and evening with a chance for showers
and possibly a thunderstorm along with MVFR cigs at RHI this
evening.
&&

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

$$

SHORT TERM.....Cooley
LONG TERM......Eckberg
AVIATION.......Cooley


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