Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Milwaukee/Sullivan WI
1026 PM CST Sat Dec 27 2014
Low clouds have been slow to exit the region this evening...with
the back edge finally working into the northwest counties late
this evening. It may take another few hours for the back edge to
make it through the rest of the area...so may have to adjust sky
Temperatures are falling into the teens in the clearing area to
the west...so adjusted lows downward across the area several
degrees. Winds will continue to weaken as the pressure gradient
MVFR ceilings around 2000 feet above ground level should gradually
exit taf sites between 05z and 07z...with mostly clear skies for
the rest of the night into Sunday morning. Gusty west winds will
continue to weaken later tonight into Sunday morning.
Cold front will shift southeast through the area around 00z
Monday...with winds shifting to the north behind it. Winds should
remain light. Should see some high clouds move into taf sites
Sunday night as well.
Small Craft Advisory was cancelled with the evening update. Gusty
west winds should remain below 22 knots for the remainder of the
night...as the pressure gradient weakens. Waves of 2 to 4 feet
toward the open waters will subside as well.
Previous discussion... /issued 222 PM CST Sat Dec 27 2014/
Tonight...forecast confidence high.
Drier and colder air is wrapping eastward through southern WI behind
departing low pressure and the associated cold front this evening.
Gusty west winds will diminish late this afternoon into this
evening. The back edge of the cloud shield is over southeast Minnesota and
eastern Iowa and will continue to make progress across southern WI
Temperatures are on the way down this afternoon behind that cold
front. Wind chills have dropped into the low to middle 20s. 925mb temperatures
drop down to around -6c overnight. The lingering pressure gradient
will keep US mixed... meaning no strong inversion developing. Low
temperatures will generally be in the lower 20s but I cannot rule out a few
locations dropping into the teens if winds go calm under clear
Sunday...forecast confidence high.
High pressure over the plains will move eastward... with the ridge
sliding through WI on Sunday. There will be plenty of sunshine
around on Sunday... although middle clouds will begin to spread into
southern WI during the afternoon. 925mb temperatures will hold steady
around -6c through the day... yielding maximum temperatures in the lower 30s.
Winds will be fairly light out of the west.
Sunday night through Tuesday night...forecast confidence medium to
A confluent flow between the northern and southern jet streams will develop
from South Dakota and NE eastward to southern WI and northern Illinois for sun nt and Monday. A weak
shortwave trough within the westerly flow aloft will pass Monday nt. At
the surface...a cold front will pass sun nt with increasing cold
advection Monday nt with the passage of the aforementioned shortwave
trough. Precipitable waters remain fairly dry at 0.25 inches or less and low level
and upper level lift is very weak...thus only have flurries or
slight chance probability of precipitation for Monday and Monday nt. A north-northeasterly onshore flow from
Lake Michigan will bring better chances for snow showers near the lake
in Kenosha and Racine counties for Monday and Monday nt...but better
chances for accumulating snow should stay in NE Illinois at this time.
Cold temperatures for Monday nt through Tuesday nt as northwesterly flow maintains an
Arctic airmass over the region. The cold...drier air will bring
some sunshine for Tuesday.
Wednesday through Saturday...forecast confidence medium.
Another cold day is expected Wednesday as another shortwave trough
within northwest flow aloft passes through the region. Brisk westerly winds
will maintain wind chills mainly below zero. The jet stream will
then transition to more zonal and even southwesterly for the 2nd half of
the week. Southwesterly surface flow and warm advection will prevail from Wednesday
nt into Friday nt with temperatures eventually returning to seasonal
normals. There will be small chances of light snow for Friday-Sat as an
upper low over the desert SW ejects east-northeastward into the Ohio River
valley. The latest European model (ecmwf) and experimental GFS are the favored
models with this system and they keep most of the snow to the
south at this time.
Drier air is spreading into southern WI in the wake of a cold front
this afternoon. Ceilings are lifting to MVFR... which should linger
through early evening before scattering out. There is uncertainty
about when the low clouds will clear. Gusty southwest to west winds
with gusts up to 30 knots will persist through late afternoon before
A high pressure ridge sliding through the region will allow for
clearing skies tonight and sunshine for most of the day Sunday with
light westerly winds. Look for middle clouds to increase north to south
late Sunday afternoon and lower through the evening.
A Small Craft Advisory is in effect through early evening for gusty
west winds in the wake of a cold front. The gusts will reach as high
as 30 knots early this afternoon...then diminish through early
evening as a ridge of high pressure builds into the region. The
offshore fetch will limit wave heights...nearing 4 feet towards open
tonight/Sunday and aviation/marine...mrc
Sunday night through Saturday...gehring