Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
602 am CST Wednesday Feb 10 2016
Updated aviation portion for 12z taf issuance
Short term...today...tonight...and Thursday
issued at 331 am CST Wednesday Feb 10 2016
Cold temperatures and lingering lake effect snow showers in
north central WI will be the main forecast concerns.
Arctic air covered the region early this morning...with 800 mb temperatures
of -20 to -24 c. Cyclonic north-northwest flow continued in the surface-800 mb
layer...resulting in a large area of lake-enhanced clouds over
NC/c WI. Downsloping winds and subsidence in the wake of a short wave
trough had cleared the skies over parts of NE/ec WI. Little precipitation
was occurring early this morning...other than scattered light lake
effect snow showers or flurries in the far north.
Have confined precipitation chances to mainly Vilas County today into
tonight...as incoming dry Arctic air should keep lake-effect
snow showers closer to Lake Superior. Favorable north-northwest wind
trajectories will persist until late tonight...then back
west-northwest toward daybreak on Thursday...leading to the demise
of lake effect. 900-850 mb relative humidity forecasts suggest that clouds
will hang tough over the region during the day...then
clear rapidly this evening (away from the Lake Superior
snow belt). A dry day is anticipated on Thursday as high
pressure passes just to our south.
Used a blend of the top performing guidance sets for
temperatures through Thursday. Highs should be in the
upper single digits to middle teens today...and lower to
middle teens on Thursday. Min temperatures tonight should be in
the single digits below zero at most locations...with single
digits above zero near Lake Michigan...and around -10 f
at some of the typical cold spots in NC WI. Winds will be
light tonight...so wind chills are only expected to be in
the teens to around 20 below zero range...too borderline for
any Wind Chill Advisory headlines.
Long term...Thursday night through Tuesday
issued at 331 am CST Wednesday Feb 10 2016
The medium range models continue to show an amplified pattern
through the end of the upcoming weekend before a more zonal regime
takes over. In this amplified pattern...a deep eastern noam trough
will lead to below normal temperatures into Sunday. The coldest
period continues to look to be Friday night into Saturday. The
European model (ecmwf) and GFS compare fairly well in regards to the low level temperatures
during this period so will use a blend. Then all sorts of timing
differences exist as the pattern breaks down late this weekend.
Thursday night through Friday night...mainly quiet...breezy and cold
on Thursday night when an Arctic cold front is driven southward by a
channeled vorticity into the Lake Superior region. Low clouds will
likely move into far northern WI ahead of the front. The combo of
temperatures and breezy west to northwest winds will drop wind chills into
the teens below zero. The Arctic front will continue to dive south
across the state on Friday. Low level lapse rates steepen but middle-
level moisture is lacking. Could see a few snow showers or flurries
develop but with little in the way of accumulations. Quite possible
that temperatures peak at midday then fall through the afternoon. The
coldest temperatures then arrive on Friday night. With a brisk northwest
wind and temperatures falling below zero....a widespread Wind Chill
Advisory is quite possible.
Rest of the forecast...Arctic high pressure moves into the region on
Saturday and Saturday night. Wind chills will be slow to rebound
Saturday morning. Forecasting temperatures on Saturday night is quite a
challenge. High pressure will be sliding east of the region late as
high clouds move into the region. Temperatures have an opportunity to tank
before this occurs...however...and will side with the colder
guidance. Clouds will be quickly on the increase on Sunday with a
chance of snow spreading across the region mainly during the
afternoon when shortwave energy arrives. Accumulations look
possible...most likely sub-advisory...but confidence is not high
with that thought. Temperatures continue to moderate into early next week
with low snow chances.
Aviation...for 12z taf issuance
issued at 552 am CST Wednesday Feb 10 2016
Lake-effect clouds with ceilings mainly in the 2000-3500 feet above ground level range
covered most of NC/c WI early this morning. Scattered snow showers were
occurring north of the rhi taf site. Clearing had occurred in
parts of NE/ec WI.
Have slowed down the clearing trend over the region today...and
kept some MVFR ceilings in the rhi/auw/cwa taf sites until late morning.
Clearing should occur across all but far NC WI by early evening.
Gusty northwest winds will subside during the late afternoon.