Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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742
FXUS63 KMKX 221615
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1015 AM CST Sun Jan 22 2017

.UPDATE...Still some patchy dense fog out, esp in the northern
cwa. By and large, observations and webcams showing improvement.
So will let the headline run its course til 18z.

PC

&&

.AVIATION/18Z TAFS/...Noting improving vsbys across the area.
Still not much flow but progs continue to suggest that we will see
gradient tighten a bit to help things along...vsby and cig wise.
Much more MVFR showing up but still seeing IFR and LIFR in spots
too. SREF suggests better redevelopment for dense fog tonight
would be north of TAF sites but all will hinge on how much wind
can be maintained overnight into Monday morning. Upstream airmass
modification is more subtle than pronounced. However 925 winds are
expected to increase from the north tonight so that may help to
keep widespread dense fog at bay with enough mixing and at least a
slightly drier airmass push.

PC

&&

.MARINE...Dense fog should improve this afternoon as west winds
spread over the region. If timing of the west winds ends up a bit
slower, the current dense fog advisory may need to be extended
past noon. Otherwise, off shore winds will continue into Tuesday
with no impacts expected at this time.

Hentz

&&

.PREV DISCUSSION... /Issued 348 AM CST Sun Jan 22 2017/

SHORT TERM...
Today and tonight...Forecast confidence is high.

Clouds and fog will once again be the main forecast challenge.
Foggy conditions will gradually improve this morning and will
maintain the current noon expiration of the dense fog advisory.
Northwest (cyclonic) flow will develop across the region today and
with low level moisture remaining high, expect stratus to
persist. Fog is once again a possibility tonight, but the current
indications are that it would be more of the patchy variety
compared to what we have observed the past several days.

Temperatures today and tonight will remain well above average.
Unfortunately, not much in the way of sunshine is expected.

Monday...Forecast confidence is medium.

We will continue in this cloudy and active weather pattern until
further notice. Low pressure will track just south of the Ohio
River Valley. This is farther south than previous forecasts and it
looks like the majority of rain will miss southern WI. Temps will
continue to be mild with highs around 40.

LONG TERM...
Tuesday through Wednesday...Forecast confidence is medium.

The next system to watch is expected to arrive Tue afternoon as
low pressure tracks across IA and nrn IL. The GFS and NAM have
been wavering north and south with their track and are a little
inconsistent with the location of the heaviest axis of precip. The
ECMWF has been very consistent with track and precip amounts, so
leaned forecast in that direction, similar to what WPC has in
their qpf.

Precip will begin as rain, but change over to snow later Tue night,
then a mix of rain and snow on Wed with temperatures right around
the freezing mark. Surface temperatures will dictate the precip
type, as there is no warm layer aloft and there should be a deep
enough cloud layer to allow for snow growth.

Models are showing a decent amount of qpf, between 0.25 and 0.50
inch. Because of the mild temperatures, not all the snow that falls
will stick to pavement, but snowfall totals could be in the 2 to 4
inch range over a 24-hour period. Tue night after midnight is the
time when highest snowfall rates are expected.

Thursday through Sunday...Forecast confidence is medium.

Cooler cyclonic flow will continue overhead through the weekend.
This will keep clouds in place and the chance for light snow
showers across southern WI. Another low is expected to drop down
from south central Canada early next week and bring a chance for
snow to WI.

AVIATION/12Z TAFS/...
Status/fog are the main forecast concerns. LIFR/IFR conditions are
common thus far this morning and should persist through much of
the morning hours until northwest winds spread into the region.
While fog should end, there looks to be enough low level moisture
to support MVFR ceilings this afternoon onward. Stratus will
linger into Monday, with some potential for IFR conditions later
tonight.

MARINE...
Areas of fog will continue through this morning. Conditions should
improve this afternoon as west winds spread over the region. If
timing of the west winds ends up a bit slower, the current dense
fog advisory may need to be extended past noon. Otherwise, off
shore winds will continue into Tuesday with no impacts expected at
this time.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY until noon CST today for WIZ046-047-051-052-
     056>060-062>072.

LM...DENSE FOG ADVISORY until noon CST today for LMZ643>646.

&&

$$
TODAY/TONIGHT AND AVIATION/MARINE...Gagan
Monday THROUGH Saturday...MRC



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