Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 211021
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
521 AM CDT Mon Aug 21 2017

Updated aviation portion for 12Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 334 AM CDT Mon Aug 21 2017

Convection trends today and tonight continue to be very
challenging.

Overnight, a weak cold front dropped into the state and at 3 am
extended roughly from central Marinette county to Wausau to
southeast Minnesota. Winds have tapered off but overall it appears
the front has stalled. A few showers developed along this front
around midnight but little or no development after that. MU CAPES
still around 1200 j/kg near this front, but little forcing at this
time as an 850 ridge slides over this morning. To the southwest
over Iowa, convection continues to develop along the cap edge and
area of greater instability. LLJ also positioned in this area.
The ECMWF appears to be handling this Iowa convection the best at
the onset, but for the today period, various models are all over
the place for convective solutions. So the question later morning
or today is the amount and timing of any convection. Return flow
and instability expected to increase this afternoon ahead of a
short wave trough approaching from the plains. Will continue to
monitor on any northeast development from the Iowa convection this
morning, especially along the frontal boundary.

Primary weather feature to likely affect the area late today and
especially tonight is the 850 trough passage. Convection was more
widespread over the Dakotas early this morning with this feature.
Pwats are progged to increase to near 2.00 and MU CAPES rebound
to the 1000 to 1200 range for the entire area. Deep layer shear
increases by tonight with the westerly flow and RRQ region of a
Jet.

850 mb trough with surface cold front slide through late tonight
or early Tuesday to end the precipitation chances from west to
east. Cooler and drier air will pour into the region on gusty
northwest winds.

.LONG TERM...Tuesday Night Through Sunday
Issued at 334 AM CDT Mon Aug 21 2017

All the action remains in the short term portion of the forecast
for this work week. High pressure at the surface will keep mostly
dry conditions in the forecast through the end of the week. As we
get towards next weekend, warm air and southerly flow are
expected to return, setting up the next chance to see active
weather in the area. Details on timing and strength will start to
become more clear in the coming days. Temperatures will be below
normal through the work week and rise to a few degrees above
normal by the end of the weekend.
&&

.AVIATION...for 12Z TAF Issuance
Issued at 521 AM CDT Mon Aug 21 2017

Patchy IFR/LIFR vsbys due to fog will linger a few hours after
daybreak due to light flow and a weak frontal boundary extending
from around MNM to AUW to SE Minnesota. Isolated convection may
develop along or near this frontal boundary today, otherwise
MVFR/IFR cigs with MVFR vsbys to become more widespread late
afternoon into tonight as a short wave trough and cold front slide
over the area.
&&

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

$$

SHORT TERM.....TDH
LONG TERM......Uhlmann
AVIATION.......TDH



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