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Area forecast discussion
National Weather Service Green Bay WI
1204 PM CST Wed Feb 22 2017

Updated aviation portion for 18z taf issuance

Short term...today...tonight...and Thursday
issued at 327 am CST Wed Feb 22 2017

Height 850 warm air advection producing mainly mid level clouds
across the region early this morning with isolated showers across
northern Wisconsin. Primary forecast issue today will be Max
temperatures with respect to the amount of clouds and light
precipitation developing over the northwest half of the state
today with the 850 front sagging southward. At least northern
Wisconsin will see more clouds today for slightly cooler but still
well above normal temperatures.

To the west, isolated storms were noted over Minnesota closer to
the mid level trough axis and north of the surface low pressure
system and warm front. Will watch the Minnesota convection this
morning for any southern adjustments with the showers as a weak
surface low tracks over central Wisconsin today. Short range progs
weaken the Minnesota convection and redevelop any light rain over
northern Wisconsin today into tonight with the sagging boundary.
Boundary layer temps begin to cool enough over the far north for a
mix late.

Southwest boundary layer winds were also producing enough
mixing and an offshore wind to keep dense fog, located over far
southeast Wisconsin and Lower Lake Michigan near the warm front,
south of the area.

Weak ridging late tonight into Thursday morning will produce a
brief period of quiet weather, along with cooler but still above
normal temperatures. Light rain ahead of the developing system
over the plains will begin to approach parts of central Wisconsin
later Thursday afternoon.

Long term...Thursday night through Tuesday
issued at 327 am CST Wed Feb 22 2017

The main concern during the early part of the forecast is with a
surface low approaching from the plains and then passing through,
or just to the south of, Wisconsin. The system will take a while
to depart, so precipitation issues linger into Saturday.

00z models were a bit more consistent than that were 24 hours
prior, but minor differences in the path of the system could
result in significantly different precipitation types and amounts.
Indications are that the heaviest snowfall will be across the
northwest part of the forecast area where 8 to 10 inches of snow
could fall over the course of about 36+ hours. Snow totals are
expected to be lower farther south and east, with some rain and/or
freezing rain keeping totals down there. Have decided not to go
with any headlines at this point since there are still questions
regarding the exact path of the system and the snowfall totals
stretch over a few forecast periods. If models take the system
even farther north the snow totals in north central Wisconsin
should be lower.

Colder air behind the system will result in high temperatures a
few degrees below normal over the weekend, with a slight warming
trend for the early part of the new work week. Some lake effect
snow showers are possible in the north into Sunday. The next
system approaching the area will bring snow and/or rain for
Monday night and Tuesday.
&&

Aviation...for 18z taf issuance
issued at 1203 PM CST Wed Feb 22 2017

VFR conditions will persist across the area this afternoon with
mid and upper level clouds spreading across the area. Then look
for ceilings to lower from north to south as a cold front sags
across the area this evening into tonight. Rain showers are also
expected over northern WI (krhi) tonight, mixing with snow
overnight, with only a few sprinkles or light rain showers
possible farther south, but some drier air is in place so the
activity is expected to be less widespread than across northern
WI. The lower cigs (mainly mvfr) will continue into Thursday
morning with some improvement by late morning or early afternoon.
Some MVFR fog is also expected across the area tonight.
&&

Hydrology...
issued at 327 am CST Wed Feb 22 2017

Glance of area rivers over central Wisconsin were near crest and
should begin falling later this morning. Although fluctations
downstream of Hydro plants will continue. Another storm system
with water equivalent of up to an inch of precipitation over 2
days approaching the region late this week. This will produce more
run off for the rivers, depending on precipitation type.
&&

Grb watches/warnings/advisories...
none.
&&

$$

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