Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 161722
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1122 AM CST Sat Feb 16 2019

.UPDATE...

No changes at this point for the rest of this afternoon into the
evening hours. Highs should top out in the low to mid 20s, with
increasing easterly breezes as we head into the nighttime hours.

Snow still looks to arrive early Sunday morning, likely starting
before sunrise in southwestern Wisconsin, and then expanding to
the northeast through mid morning. Initial take on snow amounts
suggests no major changes, though will likely need to bump amounts
up just a touch along the lakeshore, as lake effect potential
appears to have improved somewhat. Preliminary amounts still look
to range from 2-5" for most of the area, heaviest across the south
and southwest and for counties along Lake Michigan.

&&

.AVIATION(18Z TAFS)...

Deck of MVFR clouds will continue to push in from the east this
afternoon, affecting much of the area, but especially those areas
closer to the lake. Winds will become increasingly easterly as the
next system of interest takes shape to our southwest.

MVFR is likely to persist for most of the overnight, before snow
begins to move in tomorrow morning from southwest to northeast.
Expect visibility to quickly fall to IFR with the snow, with some
LIFR possible, especially closer to Lake Michigan. Snow will
persist through most of the day, with lake effect snow lingering
into early Monday morning for areas closer to the lake.

&&

.MARINE...

Winds will become stronger from the east today as low pressure
develops to our south and west. The persistent easterly flow will
result in building waves in the nearshore, at least where there is
no ice present. A Small Craft Advisory may be needed by Sunday
morning as waves start to increase toward 4-5 feet.

Winds will become more northerly and then northwesterly Sunday
into Monday as the area of low pressure moves into the Northeast.

High pressure builds back into the area early in the week, with
winds remaining fairly light. No gales are expected through the
next 5 days.

&&

PREV DISCUSSION... (Issued 330 AM CST SAT FEB 16 2019)

SHORT TERM...

TODAY AND TONIGHT...Forecast Confidence - High.

Temperatures dropped into the single digits below zero from the
Wisconsin River Valley to Fond du Lac and northward early this
morning due to radiational cooling. There is thin cirrus streaming
into southern WI that is associated with a mid level wave
approaching. Aside from mid and high level clouds, there will be no
impacts for southern WI from this feature today.

Lake effect clouds coincident with high 925mb RH expanded from Green
Bay into the Sheboygan area around midnight and have remained fairly
stationary overnight. Another area of stratus lake clouds spread
into the Chicago area. With winds turning around to the east through
the morning, we can expect the low clouds to expand across the rest
of the lakeshore counties. Flurries are likely with these clouds as
they are right around
-10C.

SUNDAY THROUGH MONDAY NIGHT...Forecast Confidence - Medium to High.

Short term guidance remains in good consistency and agreement
regarding weakening low level circulation tied to upper level jet
passing to the south of Wisconsin on Sunday.  This low level
circulation will move along a baroclinic zone draped across the
region, however the tighter thermal low level boundary will be to
the south in IL/IA.  The strongest synoptic lift with this system
across southern WI will be late tonight into Sunday morning as a
period of sloping frontogenetical forcing interacts the better
Dendritic Growth Zone.  This synoptic scale forcing weakens during
the afternoon but lingering warm air advection and low level
convergence will continue to generate lift across the area.  In
addition, lake enhancement will add to the synoptic lift during the
day as Delta-T increases to around 10-11C as the low level winds
gradually back from the east to the northeast.  The synoptic lift
shifts to the east by Sunday evening, however the threat for pure
lake effect will increase as the low level winds remain northeast
for a period of time resulting in a longer fetch.  The delta-T
increases to 13-14 degrees so expecting additional light
accumulations near the lakeshore Sunday night.  Using Cobb,
thickness and climatology techniques, used Snow Liquid Ratio`s of 15
to 19 to 1, which was lower then Superblend.  Using average QPF
around 0.18, which was close to Model Certainty mean, ended up with
snowfall mostly in the 2 to 4" range with highest amounts in the
southwest and closer to Lake Michigan. However some 5" possible in
these areas per probabilities.  A Winter Weather Advisory may be
needed for the south and east due to expected impacts on Sunday
travel, but wl let day shift make final decision.

Lingering lake effect Sunday night should taper off late in the
night into early Monday.

LONG TERM...

TUESDAY THROUGH SATURDAY...Forecast Confidence - Medium.

The extended period should start out on a quiet and cold note with
amplifying short wave ridging and a large surface high pressure area
moving across the region. The quiet weather will be short-lived
however as an upstream long wave trof over the western CONUS will be
ejecting a stronger piece of short wave energy in the midwest
Tuesday night and Wednesday.  This system will have a bit more
"kick" to it then the Sunday system and will likely bring another
round of light snow to the area beginning later Tuesday night and
possibly lingering through Wednesday night.  There remains
considerable variation in the Medium Range ensembles the track and
strength of this low pressure area.  However using a blend of the
GEM, GFS and ECMWF places southern WI squarely in a period of
synoptic scale lift during this period.  Low level temperature
profile shows mostly -sn, however a wintery mix may push into
southeast areas on Wednesday.  Once again, lake enhancement may
increase snowfall closer to the lake due to a persistent low level
easterly fetch over the mostly open waters of Lake Michigan.  SLR
will likely be in the 13 to 18 to 1 range.  Looking like a potential
for another 3 to 6" snowfall across the area.  Possible that lake
effect snow showers linger through Wednesday night before the low
level winds turn NNW by Thursday.

The persistent upstream long wave trof keeps the active weather
going towards the weekend as well, with potentially another system
bringing a wintery mix to the area around Saturday.

While the mid-level steering winds remain from the WSW, cold air
will remain firmly entrenched in the low levels.  So expect
temperatures to be below normal for most of this period.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

Update...Boxell
Today/Tonight and Aviation/Marine...Boxell
Sunday THROUGH Friday...99



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