Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
348 am CST Wednesday Nov 25 2015
Today and tonight...forecast confidence medium
Infrared and fog product satellite imagery show high clouds with a short
wave passing over southern Illinois...with an expanding band of
low/middle level clouds streaming northward with higher surface to 850 mb dew
points in a narrow ribbon lifting northward from eastern Texas/Oklahoma
through central Kansas into eastern Nebraska/western Iowa behind broad high
pressure over the eastern U.S. And in the warm air advection ahead
of disorganized low pressure in the High Plains.
The initial surge of moisture and isentropic lift will move into the
western County Warning Area late this morning and early afternoon with initial short
wave and associated surface low lifting across Minnesota into
southern Ontario...with a second surge of lift and lower
condensation pressure deficits overspreading the area late this
afternoon into tonight ahead of main trough. Will see patchy drizzle
and fog develop as lower layers saturate with higher dew point air
pushing in over the diminishing snow cover...then steadier rain with
warm...moist air riding in on strong low level flow with increasing
convergence/frontogenesis along surface to 850 mb trough.
Retreating snow cover will have a minimal impact on temperatures
today...with highs in the low-middle 40s...cooling into the low 40s in
the early evening...then rising temperatures overnight with
persistent warm advection on south winds.
Thanksgiving day through Saturday... forecast confidence medium.
Light rain and areas of fog are expected Thursday morning as weak
upward forcing continues with the low level jet pointing into
southern WI. The the better synoptic forcing will arrive in southern
WI Thursday afternoon as the upper trough and right entrance region of
the upper jet line up over US. The 925-850mb front is expected to
bisect Wisconsin from northeast to southwest at 00z Friday. The
highest rain rates will be within this frontogenetic zone over south
central and east central WI Thursday afternoon-evening. The latest storm
total precipitation amounts are around 1.5 inch for Madison and about 1
inch in Kenosha.
The rain will deplete the snow across far southern WI and we
anticipate the rapid responding rivers to rise Thursday night...including
the Fox and Pecatonica rivers. The Rock River will also likely
respond but more slowly in Rock County. Hydrologic statement
highlights this threat.
Colder air will slip into southern WI through the day Friday...
quicker in the lower levels than the upper levels. This means there
is a window of opportunity for some mixed precipitation including sleet and
freezing drizzle. Drier air will be settling in with the cold air...
so any mixed precipitation will be short-lived. Models are in better
agreement for a dry Friday afternoon and night. Surface high
pressure will set up over the Great Lakes on Saturday.
Sunday through Wednesday... forecast confidence medium.
A closed upper low over the western states will drift into the
northern plains early next week. Another mild and wet system is
expected to cross the middle Mississippi River valley on Sunday ahead
of that upper low... but the latest models keep the precipitation to the
south of the WI/Illinois border. If any precipitation would sneak into our
area... freezing rain would be possible during morning or nighttime
The upper low should cross WI Tuesday morning and bring another round of
precipitation through Tuesday night. Forecast temperature profiles support snow
where surface temperatures are below freezing.
Will keep low-level wind shear in forecast until middle-morning when
surface winds increase with daytime mixing. VFR conditions will
continue through the morning...then clouds and visibilities will begin to
lower to MVFR with patchy drizzle and fog from west to east during
the afternoon with increasing moisture ahead of an approaching
surface trough. Steady rain and fog move in as the trough sets up
from southwest to northeast across the state. Clouds/visibilities dropping
to IFR...with some lift visibilities...expected for the remainder of the
forecast. Taf sites remain on the warm side of the system so all
Extended the Small Craft Advisory to 18z Thursday in the northern
zones to allow waves more time to subside...and 00z Friday in the
southern zones for gusts to 25 knots lingering through the middle-late
afternoon Thursday after a brief lull in the early morning.
Lm...Small Craft Advisory until 6 PM CST Thursday for lmz645-646.
Small Craft Advisory until noon CST Thursday for lmz643-644.
Today/tonight and aviation/marine...rem
Thursday through Tuesday...mrc