Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 282323
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
623 PM CDT Tue Mar 28 2017

.UPDATE...
Fog and low stratus right along Lake Michigan looks like it will
creep progressively farther inland overnight. There is some
indication that after midnight, after temps cool rapidly inland
under clear skies, that stratus will accelerate quickly westward.
It will take some of the lower vsbys along with it. Dense fog is
likely right along the shore, but vsbys should improve quickly
inland. We will have to watch this closely as it has potential to
go quickly downhill.

&&

.AVIATION(00Z TAFS)...

The southeast Wisconsin TAFS, especially KMKE, will sit under the
a steady stream of low stratus and lower vsbys streaming in off
Lake Michigan. Trajectories don`t really show it improving until
about sunrise Wednesday. Very little in the way of hi resolution
guidance is handling this very well. Low IFR conditions likely
through the night. KMSN could see some IFR CIGS/VSBYS after 06z
Wed due to fog/stratus development with good radiational cooling
this evening. Conditions should lift to VFR levels by about 15z
Wednesday with MVFR cigs arriving Wednesday afternoon ahead of
approaching low pressure. Most precip should hold off until after
00z Thu.

&&

.PREV DISCUSSION... (Issued 329 PM CDT Tue Mar 28 2017)

SHORT TERM...

TONIGHT - Confidence...Medium
Main forecast challenge centers on fog and stratus trends. Things
have been rather precarious lakeside with lower ceilings/fog hugging
the shore and in some cases coming onshore with minimal inland push.
Guidance suggests some fog and stratus development further inland as
night wears on. Confidence not great at this point on inland extent
or degree of vsby restrictions due to winds staying up. Gradient
proggd to be maintained so at least some ne winds mixing down per
Bufkit. MOS and SREF not suggesting much confidence in widespread
dense so no headline at this time.

WEDNESDAY - Confidence...Medium
Focus early on will be any lingering fog/stratus and then precip
trends with WAA/moist advection ahead of system in southern Plains.
Sfc/850 millibar ese flow may help to maintain the dry layer in
place per Bufkit soundings. The GFS is much quicker to saturate this
layer in the afternoon, while the NAM shows more depth to the dry
air. Have spread POPS into the sc cwa though best moisture push
arrives beyond this period. With the cloud cover and flow off the
lake have trended cooler, more towards 3 hourly MOS and Superblend,
with the NAM mos looking better towards the lake.

Wednesday night through Friday...Forecast confidence medium.

A N-S upper trough and associated sfc trough will track from the
central and southern Great Plains to the Ohio River Valley during
this period. Well organized lift from 850-700 mb warm advection
and frontogenesis is expected Wed nt-Thu. It will be aided aloft
by the RRQD of a W-E Jet over the northern Great Lakes and srn
Canada, along with PVA from the passage of the upper trough axis.
PWS will increase to 0.80-1.00 inches with total forecasted QPF
amounts of 0.70-0.95 toward central WI with over an inch along and
south of a line from Madison to Milwaukee. Biggest challenge is
precip. type. Forecasted temps aloft toward central WI are near
0C for Wed nt-Thu AM so wanted to account for the potential for
more snow. Expecting a mix of precip. from Madison to Milwaukee
and nwd with 2-3 inches of snow forecast from Sheboygan County
wwd to MQT County. Areas of light freezing rain with a glaze of
ice will also be possible north of Madison and Milwaukee. All rain
should then be occurring for Thu afternoon into the evening. Most
of the system should then be ewd for Fri although stratus clouds
could easily linger.

LONG TERM...Saturday through Tuesday...Forecast confidence low to
medium.

High pressure will likely prevail from Fri nt-Sat nt. A fairly
large low pressure area over the Lower MS River Valley will then
move nwd for Mon-Tue bringing chances of rain for mainly Mon nt-
Tue. Precip. chances are currently low due to the uncertainty of
the track of this system. Temps will be at least slightly above
normal.

AVIATION(Update)...Large area of stratus has eroded to
the southwest of TAF sites while other lake induced stratus hugging
the shore and in some cases coming onshore. However for the most
part enough dry air mixing has eroded the inland push. Another
concern will be development of more stratus/fog overnight as
SREF/LLVL RH progs and trajectories favor some of the more
widespread stratus over the lake spreading inland as the night wears
on. However not real confident on widespread this will become or if
vsbys will get out of hand since gradient still supportive of winds
staying up. On Wednesday a low pressure system will slowly approach.
For much of the day the east or ese low level flow may help
reinforce the dry low levels but the GFS models is showing a quicker
erosion of this dry layer and a quicker onset to rain. This would
mainly affect sc WI during the afternoon while the rest of the area
looks like it would remain dry until Wednesday evening.

MARINE...At the moment, Port Washington cam shows some thicker fog
but other cams showing better vsbys. Will hold off on advisory for
now as not confident on how widespread fog will become. However have
issued a Marine Weather Statement. North winds will shift more east
around high pressure. This flow will bend northeast through
Wednesday. These winds and subsequent waves are expected to remain
below small craft levels. However the onshore flow will further
strengthen heading into Wednesday and Wednesday night as low
pressure approaches. Higher waves can then be expected with
potential small craft advisory headline needed.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Dense Fog Advisory until 9 AM CDT Wednesday for LMZ643>646.

&&

$$

Update...Davis
Tonight/Wednesday and Aviation/Marine...Collar
Wednesday Night through Tuesday...Gehring



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