Debate de meteorólogos científicos
Area forecast discussion
National Weather Service Green Bay WI
1129 am CST Monday Dec 9 2013
Updated aviation portion for 18z taf issuance
issued at 604 am CST Monday Dec 9 2013
Made updates to west-southwest headlines as accumulating snow now over in the
east. Wind Chill Advisory issued to start late this afternoon.
Still have questions on end time with system coming in later
tonight. At this time have ended it at 6am.
Short term...today...tonight...and Tuesday
issued at 411 am CST Monday Dec 9 2013
System exiting region with clearing working in this morning. In
coordination with mkx have maintained headline over the east
though have dropped west. Roads continue to have issues...with
light snow still accumulating. Issue for today is increasing winds
and falling temperatures. Wind chill values expected to
drop...meeting headline criteria around 22z and continue at least
through midnight. With current headline out will hold off on
issuing. Winds picking up later this morning...expected to create
considerable blowing of the light snow.
Tonights focus on clipper system dropping south out of
Canada...passing through WI early Tuesday. First in a series of such
systems expected to affect state. System is compact...but has some
good dynamics. Middle levels showing some instability. Have bumped
probability of precipitation up into likely category. Moisture limited...so amounts
expected to be light. Winds and temperatures moderate some ahead of
system overnight...with questions on ending time for any wind
Long term...Tuesday night through Sunday
issued at 411 am CST Monday Dec 9 2013
Models remain consistent in flattening out the mean flow over the
Continental U.S. Through the end of the week...however another upper trough is forecast
to move across the country next weekend. The main forecast issues to
be on fast-moving weak systems racing across the Continental U.S. As the flow
flattens. Trying to time these systems has been a challenge for
the models and makes precipitation timing for the latter part of the forecast
sketchy at best. After the second Arctic peaks at mid-week...temperatures
should at least warm into the 20s...but remain below normal until
The next weak weather system is fcct to move along the baroclinic
zone from the Midwest toward southern sections of the Great Lakes Tuesday
night. While any surface reflection is practically negligible...
there will be a shortwave moving through the west-northwest flow and provide enough
middle-level forcing to generate some light snow. Higher probability of precipitation to be
to our south...closer to the track of the shortwave...however the
northern extent of the precipitation may graze southern sections of the forecast area.
Any snow accumulations are expected to be minor (around one-half
inch) generally south of a isw-mtw line. For northern WI...some breaks
in the cloud cover will allow for temperatures to tank with readings in the
double digits below zero. This Arctic air...combined with west
winds near 10 miles per hour...will likely require wind chill headlines across
northern and parts of central WI. This system quickly exits to the east
on Wednesday as a large area of hi pressure builds across the central Continental U.S..
expect to see mostly sunny to partly cloudy skies and very cold
conditions across NE WI with maximum temperatures possibly not even reaching
zero over the Northwoods.
The broad area of hi pressure is expected to stretch from the Southern
Plains to the Ohio River valley Wednesday night with a northward extension of
the ridge axis moving across the western Great Lakes. While most of the
night will be mostly clear...anticipate some increase in clouds overnight
into central WI ahead of the next shortwave/onset of isen lift as
winds begin to back SW. The big story though for Wednesday night to be the
frigid conditions as min temperatures may approach 20 below zero over the
colder spots of north-central WI and even areas along Lake Michigan could dip
below zero. This little system to zip through WI Thursday morning...but
appears to be moisture starved. Anticipate at least some flurries
across the forecast area and perhaps a low-end chance pop. Either way...
not going to see much through the day with temperatures only recovering into
the single digits above zero north...mid-teens east-central WI.
As the mean flow flattens out by Friday...the crux of the Arctic air
will retreat back into Canada as 800 mb temperatures over WI rise into the -10
to -15c range. Believe the GFS is way too optimistic in bringing
the new Pacific air mass eastward and favor the colder Gem/ECMWF. Precipitation
chances look minimal as the weak isen lift continues...with the models
hinting at a small chance of snow across northern sections of the Great
Lakes. Look for maximum temperatures on Friday to be able to reach the upper teens
north...20 to 25 degree range elsewhere.
Still a lot of questions to precipitation chances Friday night into Sat as some of
the models try to bring a phasing system across the east-central Continental U.S..
if this were to occur...at least chance probability of precipitation would become necessary
mainly Friday night...but due to the uncertainty on how all of this
would play out...prefer to keep most of this period dry. An
exception could be near Lake Michigan where potential NE winds would
generate some lake effect snow showers...primarily on Sat. Model
uncertainty carries over through Sunday as the northwest flow attempts to
re-establish itself over the Great Lakes. To what extent this
occurs would determine where the baroclinic zone to set-up and
provide a track for possible clipper systems to ride. Once again...
until this pattern becomes better established...prefer to keep the
Aviation...for 18z taf issuance
issued at 1128 am CST Monday Dec 9 2013
Light snow and flurries are stubbornly sticking around
central and north-central Wisconsin at midday...and have to extend
lower visibilities in light snow into mid-afternoon. West winds will also
remain gusty through the afternoon before the gustiness subsides by
early this evening. A period of VFR conditions will then follow
until late tonight...and then a fast moving clipper type system will
bring a quick round of snow and lowering ceilings late tonight into
Tuesday morning. Visibilities in the snow to at least fall into the IFR
range...and possibly lower based on observations over Montana.
Wind Chill Advisory from 4 PM this afternoon to 6 am CST Tuesday