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Area forecast discussion
National Weather Service Green Bay WI
1037 PM CDT Fri Jul 20 2018

Updated aviation portion for 06z taf issuance

Synopsis...
issued at 314 PM CDT Fri Jul 20 2018

Showery and rather cool weather will continue into the weekend.

The strong upper system digging through the region is in the
process of carving out an eastern North America longwave trough
position which will settle into the lower Great Lakes and Ohio
Valley the next couple days. The trough will weaken early next
week, then re-energize during the middle to latter part of next
week as at least some of the energy associated with a strong
trough traveling east across southern Canada digs south into the
eastern Continental U.S..

Showers will continue at times into at least Saturday night, with
another chance for rain likely during the middle of next week.
Amounts will be quite variable, with most of the area probably
getting at least close to normal amounts. Temperatures will be a
little below normal the next couple days, warm to a little above
normal early next week, then settle back to normal late.
&&

Short term...tonight and Saturday
issued at 314 PM CDT Fri Jul 20 2018

The coverage of the showers and storms should diminish late this
evening and overnight, though it's doubtful the showers will end
completely. Coverage is expected to increase again tomorrow, when
the bulk of the showers should be over the east. Beyond those
broad trends, the specific details of the pops are difficult to
discern. Temperatures probably won't have a very large diurnal
range tonight and tomorrow due to the clouds and showers with the
upper system crossing the area. Used a blend of guidance products
for the hourly temperature grids, then built the min and Max
temperature grid from those. That technique typically works well
in situations such as this.

Long term...Saturday night through Friday
issued at 314 PM CDT Fri Jul 20 2018

Precipitation chances are the main concern during this part of the
forecast. Continued cyclonic flow around surface and 500 mb lows
will keep a diminishing chance for showers through Saturday
night. Only a slight chance for showers remains for Sunday morning
but enough instability is expected to develop during the afternoon
to carry a chance for showers in central and north-central
Wisconsin. Sunday night and Monday morning should be dry with
surface high pressure and a mid level ridge passing through the
state. An approaching cold front will combine with increasingly
unstable air to bring a chance for showers, and possibly some
thunderstorms, to north-central and parts of central Wisconsin
Monday afternoon. Another front will bring a chance for showers to
northern Wisconsin on Wednesday. The initial model blend for
Friday brought a chance for showers to northern Wisconsin on
Friday, but confidence in this is rather low due to model
differences.

Expect high temperatures to be within about 5 degree of normal
through Friday of the upcoming week.
&&

Aviation...for 06z taf issuance
issued at 1029 PM CDT Fri Jul 20 2018

A large area of low pressure over Southern Lake Michigan will
continue to drift slowly southeast into the Ohio Valley and weaken
during the taf period. Clusters of showers should gradually
dissipate overnight, except in far northeast WI. Instability has
waned, so thunder is not anticipated for the rest of the night.
With abundant low-level moisture in place and northeast flow,
expect ceilings to lower again overnight, with most places
dropping into the lower range of MVFR or IFR. Showers and a few
storms will redevelop over most of the forecast area from late
morning through the evening, and will help to keep flight
conditions in the MVFR category. The exception may be over parts
of north central and central WI, where conditions could improve to
VFR by afternoon.

Kosh...showers should end by the beginning of the taf period,
and are not expected to redevelop until late morning on Saturday.
Northeast winds and abundant low-level moisture should cause
ceilings to lower during the overnight hours, reaching the lower
range of MVFR and possibly IFR toward daybreak and into early
Saturday. Showers and isolated thunderstorms should redevelop in
the late morning and continue through the evening, along with
persistent MVFR conditions.
&&

Grb watches/warnings/advisories...
beach hazards statement through Saturday evening for wiz022-040-
050.
&&

$$

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