Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
534 am CST Wednesday Mar 4 2015
Updated aviation portion for 12z taf issuance
Short term...today...tonight...and Thursday
issued at 239 am CST Wednesday Mar 4 2015
An intense frontal boundary extending from Texas through the middle
Mississippi and Ohio Valley regions to the the East Coast will be
the focus of a variety of weather form winter storms to heavy rain
producing flooding. For northeast Wisconsin quiet but colder and
dry conditions expected for this period.
Colder air is lagging a bit this morning over eastern sections but
temperatures will start dropping for the rest of the morning.
Latest wind chill numbers just barely reaching criteria this
morning over NC WI so no headline needed...and with cold temperatures
tonight and lighter winds...will likely not be needed tonight as
Besides the potential of a Few Lake Superior clouds with light
snow showers brushing over the far north today and tonight...high
pressure will provide mostly sunny or clear and cold conditions
today through Thursday. Do note patchy clouds and flurries with a
the middle level trough over the Dakotas this morning. This trough
also contains the colder air aloft and is prognosticated to pass over
north central Wisconsin late morning into this afternoon. Will add
a brief mention of flurries and variable clouds for the north due
to the anticipated boundary layer steep lapse rates from surface
to 750 mb in cohorts with the March sunshine.
Long term...Thursday night through Tuesday
issued at 239 am CST Wednesday Mar 4 2015
Models are consistent with showing an eastern Pacific/western Continental U.S. Upper
ridge and downstream broad upper trough over east-central noam that will
persist through the upcoming weekend. This upper ridge is forecast to weaken
and shift eastward next week with a split flow developing over the eastern
Pacific. Through the weekend...main forecast to be on weak systems/cdfnts
dropping southeastward into the Great Lakes due to a mean northwest flow aloft.
Moisture appears rather sparse...thus any precipitation would be very
light. The bigger story for next week will be the potential of a
significant warm-up which would actually send temperatures above normal
for a good length of time (i.E. More than one day).
Surface hi slides into the Ohio River valley Thursday night...allowing a northern
stream shortwave trough/associated cold front to move into the western Great
Lakes toward daybreak. Models do show some modest middle-level
forcing associated with the shortwave trough...however moisture
appears limited and lift is very weak. While a few flurries may
impinge on north-central WI late...prefer to keep the forecast dry for now
and focus more on the clouds and temperatures. Do expect clouds to
gradually increase through the night which would impact min temperatures. It
still looks like mins will be reached in the evening with readings
slowly rising as warm air advection continues through the night.
The shortwave trough sweeps into the Great Lakes on Friday...while the
trailing cold front is prognosticated to reach central WI early Friday afternoon/
eastern WI late Friday afternoon. Once again...would not be surprised to
see a few flurries across parts of the forecast area...thus have
mentioned isolated wording into the forecast. SW winds preceding the
cold front...coupled with warm air advection...should bring a milder day to the
region. Look for maximum temperatures to range from the upper 20s to lower 30s.
A very weak surface ridge axis quickly pushes across WI Friday night...even
as the next northern stream system (clipper) moves into the northern
sections of the Great Lakes late. Do not believe this little surface
ridge will have enough oomph to break up the clouds...thus temperatures should
not be able to drop too far during the night. Min temperatures to range
from the middle teens to the lower 20s. As for precipitation chances...better
forcing to remain to our north and east overnight with northern WI the
most susceptible to any light snow and/or flurries. For now...
have simply thrown a small chance of light snow for the northern half of
the forecast area...mainly near the Michigan border. Forecast for Sat appeared
to be straight-forward until the GFS came in about 12 hours slower
with the clipper. Since the GFS is alone with this timing...have
ignored its solution and will favor the majority which brings a weak
area of hi pressure into the Great Lakes by Sat afternoon. Have gone
with a mix of sun and clouds with maximum temperatures ranging from around 30
degrees far north-central WI...to the middle 30s east-central WI.
This unsettled weather pattern to continue into Sunday as the next
system (another clipper) sweeps into the Great Lakes. The surface low
is forecast to track across Ontario...leaving the cold front at the surface and
a shortwave trough in the middle-levelsto try and generate precipitation. This
system does appear to have better lift/forcing/moisture than its
predecessors...thus have kept chance probability of precipitation in the forecast for Sunday. Maximum
temperatures on Sunday to again be primarily in the lower to middle 30s.
After the passage of another weak surface ridge Sunday night...the next
clipper is forecast to approach the Great Lakes late on Monday. Ahead of
this system...a prevailing SW wind will bring a surge of warm air advection into WI
with 800 mb temperatures rising above 0c. If clouds can stay away long enough
and there is no serious impact due to melting snow...there is a
real shot that some of the warmer locations in the forecast area could
surpass 40 degrees.
This clipper to remain to our north headed into on night with only
a weak surface trough sending the winds to a more westerly direction. By
Tuesday...the western Continental U.S. Upper ridge to have significantly weakened and
moved inland into The Rockies. Pacific air mass will continue to sweep
across the Continental U.S. Bringing above normal temperatures to much of the
country. Depending on cloud cover (one always has to worry about a
stratus deck from melting snow)...potential exists for the entire
forecast area to reach into the 40s. In fact...if southern areas can lose
their snow pack...temperatures in these locations could make a run at the
50 degree mark.
Aviation...for 12z taf issuance
issued at 534 am CST Wednesday Mar 4 2015
Mainly VFR conditions today and tonight with gusty west winds as
Arctic air pours into the area. An upper disturbance passing over
northern Wisconsin later morning into the afternoon may generate
isolated to scattered MVFR ceilings with flurries.