Area Forecast Discussion
Issued by NWS Green Bay, WI

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056
FXUS63 KGRB 230858
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
358 AM CDT Mon Jul 23 2018

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 355 AM CDT Mon Jul 23 2018

Satellite imagery shows an area of clouds over Lake Michigan
slowly retrograding to the west early this morning. Model progs
show this area of clouds pushing west over much of northeast and
east-central Wisconsin throughout the day. These clouds will help
shroud some of the incoming solar radiation this afternoon,
keeping high temperatures lower across northeast and east-central
Wisconsin, with higher temperatures across central Wisconsin given
more sunshine. Other than the clouds generally dry weather is
expected as a weak cold front approaches the area from the west.
Highs today will range from the lower to middle 80s across the
west, with highs around 80 across the east and lower to middle 70s
near Lake Michigan.

The aforementioned cold front will track through the western Great
Lakes region tonight, however forcing by this point will be very
weak. Therefore precipitation is not anticipated from this feature
as it tracks through tonight. Lows tonight under mostly clear
skies will range from the middle to upper 50s across the north,
with lows around 60 across the south.

A surface trough could produce some showers across eastern
Wisconsin on Tuesday afternoon as MUCAPEs rise to around 1000
J/kg. However moisture will be fairly limited with a fairly good
inversion around 700 mb. However hi-res model runs have been
fairly consistent in producing this area of showers and the
instability is impressive. Therefore will put in a slight chance
for showers across the eastern cwa with the thought that any
activity that forms will be isolated in nature, if it indeed
forms. Highs Tuesday will generally be in the lower to middle 80s
away from the lake, with highs in the middle to upper 70s near
Lake Michigan.

.LONG TERM...Tuesday Night Through Sunday
Issued at 355 AM CDT Mon Jul 23 2018

Transition to a more unsettled and cooler weather pattern will
begin Wednesday night with passage of seasonably strong shortwave
trough and attendant cold front. Thereafter the forecast area will
generally be dominated by a mean longwave trough that will
persist over the western Great Lakes region through the upcoming
weekend and into early next week. Primary forecast challenge will
revolve around timing of embedded weaker impulses moving southeast
through the mean trough. Mean temperatures will start out a few
degrees above normal mid-week, then fall off to below normal
thereafter and through the upcoming weekend.

Medium range guidance seems to have come into somewhat better
agreement on timing of cold front across the area Wednesday night.
Appears frontal passage will occur roughly between 06 and 12 UTC
Thursday morning. Given robust upper dynamics and strength of
mid-level winds with primary shortwave trough, coupled with
modest instability Wednesday afternoon into early evening,
showers and thunderstorms will be most widespread across Minnesota
and the western half of Wisconsin ahead of the approaching cold
front. Forecast soundings across central Wisconsin ahead of the
front early Wednesday evening once again suggest somewhat modest
instability of 500 J/kg to perhaps 1000 J/kg, but given
relatively strong dynamics, and increasing deep layer shear of 30
to 40 kts, concur with SPCs introduction of a marginal risk of
severe storms into central Wisconsin. Appears best chance of an
isolated severe storm or two would be west of the Fox Valley prior
to 06 UTC Thursday. Further east, instability will likely be
waning given nocturnal stabilization and would expect a general
weakening trend as convection sweeps across eastcentral Wisconsin
roughly between 06 UTC and 12 UTC Thursday morning. Overnight
rainfall amounts will be modest generally in the 0.25 to 0.50 with
the highest amounts over central Wisconsin.

In the wake of the frontal passage Thursday morning, robust CAA
will dominate the forecast area thus expect a cooler and rather
breezy day with afternoon temperatures ranging from the upper 60s
over northcentral Wisconsin to the mid 70s elsewhere. Medium range
guidance has also maintained signal of a weak secondary impulse
dropping into northern Wisconsin Thursday afternoon during peak
heating, thus maintained chance pops for scattered showers there
until about 00Z Friday. Thereafter, forecast confidence becomes
low with respect to additional transient weak impulses traversing
the mean trough position Friday. Best guess would be some
diurnally driven afternoon showers across the north on Friday with
a better chance for more widespread shower activity sometime on
Sunday with another frontal boundary approaching from the
northwest and a low pressure system progged to pass just to the
southeast of the forecast area.

Saw no reason to deviate from latest model blend of forecast high
temperatures for the later half of the week into the upcoming
weekend which indicate values trending below normal.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1149 PM CDT Sun Jul 22 2018

Models are suggesting that more moisture and clouds will push
west into eastern WI late tonight into Monday, so have made some
adjustments to sky cover and ceilings in northeast and east
central WI. Will carry a period of MVFR ceilings along the
lakeshore during the morning and early afternoon, but not sure if
MVFR flight conditions will get into GRB/ATW/OSH. Will leave
those sites in the lower end of VFR for now.

Otherwise, patchy fog is expected to develop over north central
and parts of central WI overnight, along with MVFR/IFR
visibilities. Think there will be just enough surface and boundary
layer winds to prevent fog development in eastern WI.

Light northerly winds will become east in the Fox Valley and
Lakeshore areas late Monday afternoon.

.KOSH...Mostly clear skies are anticipated overnight. There is a
very low probability of fog late tonight, but surface and boundary
layer winds should prevent any significant development from
occurring. Clouds will wrap back in the from the east in the late
morning, with BKN conditions occurring toward midday. Right now,
it appears that ceilings will stay in the lower end of the VFR
flight category, with ceilings of 3500-4000 ft AGL. Clearing
should occur in the evening. Light north winds should veer east
off Lake Winnebago in the late afternoon.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......ESB
AVIATION.......Kieckbusch



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