Forecast Discussion for GRB NWS Office
000
FXUS63 KGRB 180751
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
251 AM CDT Wed Jul 18 2018

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Thursday
Issued at 251 AM CDT Wed Jul 18 2018

High pressure over the western Great Lakes will keep the weather
quiet with mostly clear skies today and tonight. After some
isolated morning fog, mainly across the north, highs today will
rebound a bit into the upper 70s to lower 80s away from Lake
Michigan, with highs in the lower 70s near the lake as the high
drifts east and the area gets on the backside. Some fair weather
cumulus clouds are once again expected today, although coverage is
not expected to be as high as yesterday. Clouds will increase
tonight as the high continues to move east and a low pressure
system approaches from the west, with overnight lows a bit warmer
ranging from the middle 50s to around 60 degrees.

The aforementioned low will approach from the west on Thursday,
bringing increasing chances for showers and a few thunderstorms
from west to east as the day progresses. The best chances will be
across the west closer to the approaching low with fairly small
chances or dry conditions expected across the east. Instability
on Thursday is relatively paltry along with a fairly weak wind
field, therefore nothing more than a few rumbles of thunder are
expected from thunderstorms during this period. Highs on Thursday
will range from the middle to upper 70s across the west with
increased clouds, with highs around 80 further east away from the
lake. Near the lake highs will be in the lower to middle 70s.

.LONG TERM...Thursday Night Through Tuesday
Issued at 251 AM CDT Wed Jul 18 2018

Forecast concerns mainly revolve around precip chances and trends
from Thursday night through this weekend when a slow moving upper
low traverses the region.  The ecmwf and gfs have come into better
agreement over the past 24 hours, so a blend of these models should
suffice.

Thursday night through Friday night...Compact yet potent upper low
will move across eastern Minnesota and western Wisconsin on Thursday
night.  Ahead of the low, increasing elevated moisture transport via
30 kt low level jet and instability upwards of 400-600 j/kg will
lead to the shower and thunderstorm threat increasing from southwest
to northeast across the region during the evening.  Additional
periods of showers and storms can be expected overnight on Thursday
night through Friday evening as the vertically stacked low travels
across central to northeast WI.  Coverage of storms may see an
uptick on Friday afternoon as a result of surface based heating,
particularly over eastern WI where SB capes over 1000 j/kg will be
possible if clouds do not hold back temps.  Deep layer shear looks
too marginal for any severe storms, though suppose cannot rule out
an isolated cold air funnel. Even though the low will move into the
Upper Peninsula on Friday night, cloud cover looks to remain fairly
widespread, with scattered showers over northern WI. Due to the
clouds and precip, temps on Friday will only reach into the low to
mid 70s.

Rest of the forecast...The low pressure system will continue to spin
over the vicinity of northern Lake Michigan on Saturday and Saturday
night, and will generate scattered showers at times, most widespread
over northern WI.  As the low finally pulls away on Sunday, should
see skies gradually clear from west to east after a mostly cloudy
start.  Wouldnt be surprising to see a few sprinkles  persist into
the morning hours.  A significant change in the model solutions
takes place early next week as the models now advertise another cold
front moving through on Monday or Monday night, which could trigger
additional precip chances. As flattened upper troughing settles
overhead, temps will remain near or slightly below normal into early
next week.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1001 PM CDT Tue Jul 17 2018

VFR conditions will prevail through Wednesday evening, the only
exception would be for some patchy fog (MVFR visibilities) across
north-central Wisconsin Fair weather cumulus clouds at 5 to 6
thousand feet will dissipate around sunset, then redevelop again
after 16z on Wednesday. Light winds overnight turn southerly
later Wednesday morning.
&&

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

$$

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

NWS GRB Office Area Forecast Discussion