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Area forecast discussion 
National Weather Service Green Bay WI
905 PM CST Sat Feb 13 2016

Updated aviation portion for 06z taf issuance
and new information added to update section

issued at 901 PM CST Sat Feb 13 2016

Watching how temperatures are reacting out appears we won't get
much recovery until middle clouds arrive. The leading high clouds will
probably only put the brakes on the fall. Meanwhile...temperatures across
the north have already plunged to near forecast mins. With continued light winds
and clouds not making it into that area until late tonight/toward
morning...will need to lower mins across the north. Will probably also
adjust temperature trends in central WI to have mins occur earlier in the
night...with some rebound late.

New NAM now a little more generous with snow potential in east-c WI
tomorrow. Won't make any changes to precipitation amnts this evening...but
will slow the arrival of the precipitation into central WI a bit.

Updated product suite will be out within 30 minutes.

Short term...tonight and Sunday
issued at 219 PM CST Sat Feb 13 2016

Main forecast focus to be on the impending light snow event arriving
on Sunday and continuing into Sunday night.

The 20z msas surface analysis indicated a ridge of hi pressure stretched
from western Ontario southeastward through western WI to the middle-MS valley. A very
weak area of low pressure was situated over eastern Upper Michigan with a trough
extended westward toward iwd. Farther west...a series of weak low pressure
areas were located over the Front Range of The Rockies from
satkatchwan to NE nm. Vsbl satellite imagery showed a large area of
clouds over the central/northern plains as warmer air attempts to push
back at the Arctic chill over the northern tier of states.

The surface ridge axis will push across WI this evening and already be
approaching the eastern Great Lakes by daybreak. Expect to see a
period of calm or nearly calm winds through much of the night over NE
WI...thus temperatures should have no problem dropping below zero across
all but the immediate Lakeshore counties. Look for min temperatures to
range from around 15 below zero over parts of northern around
zero across Door County. Do not anticipate the need for another Wind
Chill Advisory tonight due to the very light winds. Nonetheless...anyone
going out tonight should be prepared for another very cold night.

Weak low pressure is forecast to consolidate over the northern hi plains and
move southeast across the northern plains along a modest warm front situated over
the Midwest on Sunday. There are several factors that need to be
dealt with. For starters...the air mass over NE WI is initially
very dry with forecast soundings indicating we would not saturate
completely until Sunday afternoon. Secondly...the better isen lift
will stay to our west and south...perhaps brushing southern sections of
the forecast area. Third...the S-southeast winds could bring a lake effect
snow band to the Lakeshore counties during the afternoon.
Lastly...models continue to show a very deep dendritic growth zone...
so if enough lift and saturation can be realized...this could add to
a higher snow total. Current thinking is to have a snow
accumulation range from one-half inch or less north and E-cntrl...
one-half to one inch central and Lakeshore by 00z Monday. Maximum temperatures
should be warmer with readings in the middle to upper teens north and
central...lower 20s east-central WI and Lakeshore.

Long term...Sunday night through Saturday
issued at 219 PM CST Sat Feb 13 2016

For the new work week...a few swings with temperature trends
expected along with a couple of precipitation chances.

First forecast issue centers on the Sunday night into the early
Monday morning as a middle level short wave trough drops southeastward
over the western Great Lakes region. Dry air will hold off precipitation
over northeast Wisconsin Sunday evening before some saturation
occurs. Surface trough gradually tracks over later Sunday night
before departing Monday morning. With the cold air in
place...eventually a deep snow growth region develops so a few
inches of snow possible with the higher amounts over central
Wisconsin. Lake enhanced snow could play a role Sunday night for
mainly Door County as winds turn more S/southeast for a duration Sunday
night. Onshore winds along Kewaunee and Manitowoc not deep with
850 winds generally southwest Sunday night.

With upper height increases...temperatures moderating to near
normal Monday into Tuesday...but then trend down toward Wednesday
due to a passing clipper southwest of the area. But this will be
short lived as the western states upper ridge moves into the
plains...and a mild trend is on the way. Forecasts suggests h850
temperatures warming to +4 to +10 by Friday depending on the model run.
The warm advection and precipitation chance will produce type issues later
in the week...especially Thursday night.

The 12z GFS run suggests the warming will continue into the
weekend...while the European model (ecmwf) briefly ends the warming trend Sunday
with a clipper type system. Nevertheless going forecast temperatures
will put a big Dent in the snow cover.

Aviation...for 06z taf issuance
issued at 901 PM CST Sat Feb 13 2016

Generally good flight conditions /VFR/ expected tonight. Conditions
will start to deteriorate tomorrow as light snow overspreads the
area. In eastern clouds and some flurries/snow showers off Lake
Michigan will probably bring MVFR conditions to the Lakeshore by
middle-late morning.

Grb watches/warnings/advisories...


short term.....AK
long term......tdh

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