FXUS63 KGRB 051956
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
256 PM CDT Thu Aug 5 2021

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Friday
Issued at 255 PM CDT Thu Aug 5 2021

A mid level disturbance will continue to produce scattered showers
and isolated thunderstorms this evening as it tracks east through
the forecast area. The MLCAPEs are fairly low; therefore, only
general thunderstorms are expected. Lows tonight are expected to
fall into the lower to middle 60s across the region.

A weak surface trough will track through the western Great Lakes
region on Friday. MLCAPEs on Friday will be much higher than
today, rising to 1000 to 2000 J/kg across central and east-central
Wisconsin during the afternoon hours as temperatures rise into the
upper 70s to lower 80s. Despite the decent CAPE values, shear will
be fairly weak as 0-6 km bulk shear values are only around 10
knots. Given the high MLCAPE values an isolated strong to severe
storm with gusty winds and large hail is possible; however, given
the weak shear widespread severe weather is not expected.

.LONG TERM...Friday Night Through Thursday
Issued at 255 PM CDT Thu Aug 5 2021

An active pattern will continue into the first half of next week
with progressive 500mb flow. Temperatures should run near or above
normal on most days through the period. 

Models continue to show 1,000 to 2,000 J/KG of CAPE Friday
afternoon into early Friday evening. 0-6km shear values around
20 knots. Could not rule out an isolated strong or severe
thunderstorm early Friday evening. Wet bulb zero heights around
13,000 feet. A few of the storms could produce strong winds and
hail, along with torrential rainfall.  

There will be a break in the rain later Friday night into Saturday
morning. Additional storms expected to develop Saturday afternoon
across western Wisconsin and Minnesota Saturday afternoon. Some of
these storms could make it into central and north-central
Wisconsin by 00z Sunday. The cluster of thunderstorms is expected
to move across the area Saturday night. A few of the storms could
contain strong winds, hail and torrential rainfall. The Day 3
Storm Prediction Center Outlook has much of the area in a
marginal risk of severe storms Saturday night into Sunday morning. 

For Sunday, additional thunderstorms are expected to develop 
Sunday afternoon and move across the area along a warm front
(ECMWF). Depending on how much clearing takes places, some of
the storms could become strong or severe as well. On Monday, the
500mb trough is expected to move across the western Great Lakes
bringing additional chances of showers and storms. Some of these
storms could be on the stronger side as well. Beyond Monday,
progressive flow in the 500mb pattern will result in broad brushed
chances of showers and storms for the remainder of the forecast 
period.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1229 PM CDT Thu Aug 5 2021

Middle clouds and some low cumulus clouds have increased across
the area ahead of an upper level disturbance approaching from the
west. The disturbance will produce scattered showers or
thunderstorms in central and north-central Wisconsin this
afternoon and evening, as already evidenced by upstream doppler
radar.

Scattered showers are possible across the entire region tonight 
as the upper level disturbance moves east. IFR ceilings are 
possible in central and north-central Wisconsin after midnight as
low level moisture increases.

A weak surface front will bring scattered showers and
thunderstorms Friday, mainly during the afternoon. MVFR/IFR 
conditions in the morning should improve to VFR by late 
afternoon.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......Eckberg
AVIATION.......Kurimski