Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 151557
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
957 AM CST Sun Jan 15 2017
Quiet conditions today and tonight with surface high pressure in
control. Our attention immediately turns to the southwest, where
our next weather maker is emerging. A closed upper circulation,
now evident in moisture channel imagery over northern Mexico, will
lift northeast into the lower Missouri valley on Monday, while
escorting a surface low along a similar path. This system will
bring mixed precipitation to southern Wisconsin starting Monday
morning/early afternoon and continuing into Tuesday. With cold
surface temperatures and a warm layer aloft, the greatest concern
is for freezing rain on Monday afternoon into Monday night.
Surface temperatures look to remain below freezing for much of the
day along and northwest of Madison, and this is where our concern
is greater for a potentially longer duration icing event. Will be
assessing new model data through the morning, with the intention
of issuing any potential headlines later today.
VFR conditions today. High clouds will gradually shift north this
afternoon and lower tonight ahead of the next system to affect our
area on Monday. Precipitation should begin from the south late
Monday morning or early afternoon with a mix of precipitation
types. Light freezing rain is possible Monday afternoon and
evening, with the greatest odds from Madison northwest.
Precipitation may transition to all rain at the southeastern
Lakeshore sites, such as MKE and ENW.
The light winds will continue through tonight as high pressure
passes across the western Great Lakes. Light offshore winds
will eventually turn SE on Monday as low pressure approaches
from the central and southern Plains. The onshore winds will
approach Small Craft Advisory levels Monday night and again Tuesday
night into Wednesday as the low pressure area departs the region.
Hi res visible imagery from Saturday afternoon showing patchy thin
ice in the nearshore waters of Lake Michigan, with thicker ice
closer to shore from Milwaukee county south to Winthrop Harbor. The
ice will likely grow and thicken today, but will likely thin and
break up later Monday into Tuesday as winds increase and warmer air
moves across the lake.
.PREV DISCUSSION... /Issued 300 AM CST Sun Jan 15 2017/
TODAY AND TONIGHT...Forecast confidence is High.
The upper level winds across Wisconsin are zonal and we are in the
entrance region of the jet max across the Great Lakes and northeast
U.S. By late tonight we are in the right entrance region, providing
an increase in upper divergence and a small increase in upward
motion. Meanwhile the southwest U.S. shortwave only enters the
southern plains around sunrise, with the weak mid/upper ridge axis
still over Iowa and the mid Mississippi valley. The 850 and 700 mb
southwest jet max is still across Missouri with 850 and 700 mb
saturation just south of the Illinois border. Therefore only a very
small chance of precipitation by sunrise, mainly southwest of
Madison. Airmass initially cold so any precipitation likely to
start as very light snow. Even this is problematic given the dry
air initially across southern Wisconsin.
High/mid Clouds will thicken today as jet-level moisture
increases across southern Wisconsin. Surface high pressure remains
across southern Wisconsin today and tonight.
MONDAY AND MONDAY NIGHT - Confidence...Medium
Still looking like a messy day across parts of the area. Early on
the models do show some lingering ridging in the low levels along
with better dynamic forcing more to our south and southwest with
the mid level vort center. So the initial push of precip will be
tied to initial surge of waa/moist advection along with the right
rear quad of upper jet across the Grt Lakes region. A pronounced
warm layer will be in place and the key will be sfc temps. The GFS
MOS 3hrly temps show readings 3-5 degrees colder than the NAM.
Predominant low level flow will be from the east so thermal
advection likely to be initially limited and cloud cover likely to
inhibit the normal morning boost so the colder numbers have some
merit. Prior to warm layer push some initial snow is plausible but
dry airmass may limit that potential. The NAM and ECMWF show a
stronger push of moisture in the 12-18z time frame while the GEM
and GFS show lighter qpf into the far south in that timeframe.
Clearly the GFS keeps the concern for the fzra longer than the NAM
which could last into the evening hours. Mid level shortwave along
with surface/850 low passage will enhance vertical motion fields
Monday night. For now leaning towards a blended solution with
areas of nrn and wrn cwa most vulnerable to a longer period of
fzra than the south or southeast. Still think a headline will
likely be needed to handle this potential icing scenario.
TUESDAY - Confidence...Medium
Surface/850 low lifts northeast from cntrl/srn WI. Secondary mid
level wave drops in and some weak caa begins with the NAM showing
the coldest temps. Some changeover to some snow heading into Tuesday
evening when core of coldest 850 temps slide across.
WEDNESDAY - Confidence...Low to Medium
The Euro ramps up the waa with a swath of light precip well to our
north and 850 temps reaching 6 or 7c. Meanwhile the GFS shows a
stronger vort arriving from the northwest with no qpf. With the GEM
and Euro going with the dry look and the GFS showing little lower
level forcing will keep the dry look for now.
THURSDAY - Confidence...Medium
Decent agreement for mild airmass to be in place. 850 temps
averaging 7c to 9c. Will be keeping an eye to the southern Plains to
see how the energy there ejects out. The GFS and GEM look similar
with a broader low while the GFS holds things back into TX. In all
model solutions though the area looks dry though the GEM and Euro
show precip with the 500 low in the Plains nudging closer.
FRIDAY AND SATURDAY - Confidence...Medium
While differences remain the general idea is to keep the mild
pattern in place with a low lifting northward through the Plains.
LLJ looks to become a bigger factor heading into Saturday.
AVIATION/12Z TAFS/...High pressure across southern Wisconsin into
tonight will allow for light winds. High clouds to the south of the
area will gradually shift northward this afternoon and tonight lower,
ahead of the next system that will affect the area Monday. Do not
expect any precipitation until near sunrise mainly southwest of
madison, and this would only be a small chance.
MARINE...High pressure across southern lake Michigan will bring
light winds into tonight. Winds will remain rather light into Monday,
before increasing Monday night. A Small Craft Advisory may be needed
for Monday night in later forecasts.
Low pressure moving northeast through far southeast Wisconsin early
on Tuesday should bring lower winds once again. Gusty west winds are
possible Tuesday night into Wednesday, as the low moves out of the
TODAY/TONIGHT AND AVIATION/MARINE...Collar
Monday THROUGH Saturday...Hentz