Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 190923
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
323 AM CST Thu Jan 19 2017

.TODAY AND TONIGHT...Forecast Confidence Is Medium.

First issue is the persistent low stratus and fog over most of the
area. There are a few areas where the clouds have mixed out in the
south and southwest counties. However, more low stratus may move
northeast into the area from the southwest, within weak warm air
advection regime. Models have not handled these low stratus clouds
well.

The low status may linger through today, though winds at top of
inversion may try to mix out these clouds in spots. Tried to keep
things mostly cloudy for today. Fog has become dense in the far
southwest counties early this morning, and issued a Dense Fog
Advisory there until 15Z. The fog should linger across the rest of
the area this morning, improving somewhat this afternoon.

The main 500 mb low will shift from the southern Plains into
northwest Iowa today and tonight, becoming negatively tilted tonight
across the region. Initial differential cyclonic vorticity advection
by 00Z Friday should help bring leading edge of rain into the area.
Rain will continue tonight, as another shot of differential cyclonic
vorticity advection pushes northward through the region. Kept high
end PoPs for mainly tonight across the area.

It appears that most of the precipitation will remain rain across
the far northern portions of the area later today into tonight.
Surface temperatures should remain above freezing, with ice crystals
present in area forecast soundings. So, not much in the way of
freezing rain is expected in the far northern counties. Despite the
clouds, highs should reach the upper 30s to lower 40s today. Lows
tonight should be in the middle 30s in most areas.

.FRIDAY...Forecast confidence is high.

Negative tilt shortwave trough lifts north through the upper
Mississippi Valley/lower Great Lakes. Dynamic support will be
present into the early afternoon, as channeled vorticity coupled
with weak jet-level divergence passes through. Rain shower chances
should persist into the afternoon before the forcing for ascent
wanes. With saturated low-level profiles on area forecast soundings,
cloudy skies will be the rule. Given 925 mb temperatures of 1 to 4
degrees Celsius and moist adiabatic lapse rates, highs should reach
the upper 30s north to the lower 40s south.

.SATURDAY AND SUNDAY...Forecast confidence is medium.

Yet another upper low lifts north from the lower Missouri Valley
Saturday morning and into northern Minnesota and Wisconsin by Sunday
evening. An occluding surface low takes a similar path, skirting by
to our west, while drawing warmer air into our area on southerly
winds. While we`ll see a slight chance for rain showers in
southern Wisconsin, the better rain chances remain to our west
over Minnesota and Iowa and closer to the better dynamic and
thermodynamic support. Thermal advection boosts 925 temperatures
to around 5 to 7 degrees Celsius on Saturday, supporting very mild
highs in the upper 40s/lower 50s given moist adiabatic profiles.
Slightly cooler air will spill in behind the departing low on
Sunday, but we should still make it well into the 40s for highs.
Skies will be mostly cloudy to cloudy given plenty of low-level
moisture through the period.

.MONDAY THROUGH WEDNESDAY...Forecast confidence is medium.

Most of the wave train action remains to our south into Tuesday
as a strong and expansive low pressure system tracks from the
Tennessee Valley/Gulf Coast States into New England. We could see
a few rain showers on Monday or Tuesday on the back side of this
system, with some mixed precipitation possible. Models disagree on
the strength and placement of the next upper level wave riding
southern stream energy towards the mid Mississippi Valley on
Wednesday. Temperatures will be cooling by this time, so any
precipitation, if present, could be in the form of snow.

&&

.AVIATION/12Z TAFS/...

Low stratus clouds with ceilings below alternate minimums, and
approaching airport minimums, are expected to linger across most of
the area this morning into the afternoon. There may be holes that
develop in this deck at times. Visibilities should generally remain
around 1 mile or higher this morning, improving this afternoon. An
exception will be southwest of Madison, where 1/4 mile dense fog
will occur into the middle morning hours.

Rain with more low ceilings and visibilities down to near alternate
minimums are anticipated to push north into the area later today
into tonight. Winds will remain light. Could see dense fog in spots
later tonight, though most areas should remain higher.

&&

.MARINE...

Southwest winds this morning will back to the southeast this
afternoon, and remain light. Any fog over the waters should remain
above 1 mile this morning, with more expected by later tonight.
Generally light winds are expected into Saturday night across the
area. North to northeast winds may pick up somewhat on Sunday,
though will still be below Small Craft Advisory levels. The light
winds should linger into early next week.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY until 9 AM CST this morning for WIZ062-067-
     068.

LM...None.
&&

$$

TODAY/TONIGHT AND AVIATION/MARINE...Wood
Friday THROUGH Wednesday...SPM


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