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Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI
924 PM CST Friday Nov 27 2015

Update...expect high clouds brushing southern WI to thin and push
off to the east and south overnight as baroclinic zone gets nudged
southward. 850-700mb flow still expected to turn northeast
overnight as dry air above 3k feet settles in. Weak convergence
may yet produce a few flurries and sprinkles overnight from southern
Milwaukee County southward.

High clouds obscuring some breaks in the low clouds across eastern
County Warning Area last hour or som. Main back edge of the low clouds over
central WI...should work its way slowly southward and should affect most
of southern WI away from lake by late tonight into Sat morning. Southeast WI
should be last to clear out on Sat due to expected lake effect
clouds. Only minor tweaks to min temperatures overnight.


Aviation/06z tafs/...low level onshore flow should cause low
clouds to persist longer in the southeast. Otherwise expect low
clouds to continue slow erosion overnight into early Saturday. Not
impossible a few flurries or sprinkles may get shaken out of low
clouds at kmke and kenw from weak lake effect overnight.


Marine...high pressure nosing into Wisconsin has weakened the
pressure gradient enough to allow winds to diminish below Small
Craft Advisory levels across northern marine zones. Lingering
tight gradient still contributing to gusty winds across southern
zones. Will continue Small Craft Advisory timing to allow waves to
diminish gradually overnight. Possible that higher waves may
linger into early Saturday morning in southern marine zones due
to north to northeast winds persisting at 10 to 20 knots.


Previous discussion... /issued 314 PM CST Friday Nov 27 2015/

Short term...

Tonight and Saturday... forecast confidence high.

Brisk north winds ushered colder air into southern WI throughout the
day in the wake of a cold front. The 850mb frontogenesis is just
exiting southeast WI late this afternoon. There are a few light
showers/ flurries associated with this band.

Low clouds extend back to northwest WI this afternoon. The back edge
will erode from northwest to southeast through the night... inline with 850-500mb
dry air. That dry air will not make it into southern WI until around
midnight and will probably not clear southeast WI until closer to
Sat morning. Min temperatures will be highly dependent upon the
cloud cover... but trended warmer with this forecast except toward
central WI.

Persistent north winds over Lake Michigan will start to take on a
convergent pattern tonight. The mesoscale models are picking up on a
dominant lake effect cloud band setting up over southeast WI and
northeast Illinois late tonight through Saturday morning. Delta-T values
are marginal for snow showers... but sprinkles/flur99
tonight/Saturday and aviation/marine...99
Saturday night through Friday...99ries would not be
out of the question. Left precipitation mention out of forecast but
increased sky cover in far southeast WI through Sat morning.

Saturday night and Sunday...forecast confidence high.

As a west 250 mb upper level 130 knot speed maximum exits northern
Illinois upper level ridging occurs over southern Wisconsin.
Nearly neutral upper level convergence occurs with mainly 700 mb
downward motion...except for a few bands of weak upward motion
pushing north through the forecast area Sunday. 700 mb relative humidity
increases Sunday with the 850 mb layer very dry. Lower level lake
clouds persist over the far southeast into Saturday evening.

Surface high pressure is centered over the upper Mississippi
Valley and upper Great Lakes with light northeast w99
tonight/Saturday and aviation/marine...99
Saturday night through Friday...99inds.

Sunday night and Monday...forecast confidence high.

The upper ridge pushes east to the Great Lakes Monday as a
diffluent southwest flow develops ahead of a closed upper low
over the eastern Wyoming and northern South Dakota area. Weak
upper level divergence begins late Sunday night and increases
Monday. 700 mb upward motion is weak until Monday afternoon when
it increases...especially late afternoon. The 700 mb relative humidity increases
Sunday night and saturates Monday. 850 mb layers remain dry but
saturate in far southwest Wisconsin and northeast Illinois towards
tonight/Saturday and aviation/marine...99
Saturday night through Friday...99

The GFS does bring precipitation across south central Wisconsin
late Monday afternoon. Thickness and thermal profiles would
indicate rain.

Long term...

Monday night and Tuesday...forecast confidence high.

The upper low should move east Monday night and into Wisconsin
Tuesday. This will bring precipitation Monday night...then
diminishing from the south Tuesday. Colder air will wrap into
southern WI from west to east Monday night. The 12z GFS has
trended towards the European model (ecmwf) with the cooling. Therefore the
transition to a mix of snow is expected mainly lat99
tonight/Saturday and aviation/marine...99
Saturday night through Friday...99e Monday
night...except far east. By Tuesday the upper levels are cold
enough for snow...but the boundary layer is still rather
warm. Southern WI could see some light deformation area snow or
rain snow mix Tuesday afternoon and evening...with little

Tuesday night and Wednesday...forecast confidence medium.

The GFS is still a little quicker in moving off the upper low...
but has trended towards the slower European model (ecmwf) with the low over lower
Michigan and the Lake Huron area Wednesday morning.

Thursday and Friday... forecast confidence medium.

The northwest flow Thursday gives way to a trough over the
Ohio and Tennessee Valley area Friday. The transit99
tonight/Saturday and aviation/marine...99
Saturday night through Friday...99ion at middle
levels is a little different between models Thursday.

The GFS and European model (ecmwf) are dry.

Aviation/00z tafs/...

Colder and drier air is working into southern WI today on gusty
north winds. An MVFR cloud deck extends well back into northwest
Wisconsin. Shortwave energy over Illinois/in should keep the MVFR cloud
shield intact through late evening... and a little longer in far
southeast WI. Scattered VFR clouds expected through Saturday morning
before clearing. North winds will become lighter overnight as high
pressure settles in.

Southeast WI near the lake...from Milwaukee to Kenosha... may be
impacted by a lake effect cloud band. Models have been hinting at
this for the past couple of days. Not expecting measurable precipitation...
but 1500 feet or lower ceilings with sprinkles or flurries will be
possible from just after midnight through Saturday morning.


No change to the Small Craft Advisory. Winds over the northern
marine zones look to ease below advisory levels by midnight... while
winds and waves will be slower to subside in the southern zones as
gradient will be slower to slacken with weak surface wave moving up
along or just north of the Ohio River valley. Light winds and quiet
weather are expected for the rest of the weekend.


Mkx watches/warnings/advisories...
Lm...Small Craft Advisory until 4 am CST Saturday for lmz645-646.

Small Craft Advisory until midnight CST tonig99
tonight/Saturday and aviation/marine...99
Saturday night through Friday...99ht for lmz643-644.




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