Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 221516 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
916 AM CST Thu Feb 22 2018

.UPDATE...

Regional radar continues to light up with scattered returns this
morning, but a formidable dry layer in the low levels persists.
Short range model soundings maintain this dry easterly flow in the
lowest 5-10kft through the early/mid afternoon hours, so the
battle between mid level moisture/lift and low level dry air will
continue. Current ASOS/AWOS observations continue show cloud bases
in the 6 to 10kft range, so at this point any flakes that could
reach the ground would be isolated in nature.

In talking with our neighbors there are pockets where convective
elements have produced measure snowfall at the surface. Mainly
across northeastern Iowa. Given the convective nature of the
precipitation, this is more hit/miss than widespread. Given
persistent radar returns over our western areas, I went ahead and
bumped up PoPs and went with scattered snow shower wording. A
light dusting of accumulation is possible in widely scattered
locations from Sauk to Iowa to Lafayette counties.

Will be diving into the complex precipitation evolution for
tonight as the new data arrives. At this point, all looks on
track, but minor modifications/tweaks are likely.

&&

.MARINE...
Northeast winds this morning will shift to easterly this afternoon
and increase with time. Waves will increase to 3 to 5 ft this
afternoon, and build to 4 to 7 feet tonight. A Small Craft
Advisory remains in effect.

Winds will become westerly Friday as low pressure exits, but
become east-southeast again later Saturday and Sunday in advance
of our next low pressure passage. Still looking at the potential
for strong low pressure to move through the Great Lakes region
Sunday, with increasing winds and waves in response.

&&

.PREV DISCUSSION... (Issued 519 AM CST Thu Feb 22 2018)

UPDATE...

Dry air in lower levels should result in mainly VIRGA south
central this morning, although some light snow may make it down.
Then another surge of precipitation reaches the ground later this
afternoon and evening.

AVIATION(12Z TAFS)...

VFR will prevail into the afternoon hours, before ceilings begin
to lower in response to an approaching trough. Dry air in lower levels
should result in mainly VIRGA south central this morning,
although some light snow may make it down. Expect to see ceilings
fall into MVFR tomorrow afternoon, and then eventually IFR late
Thursday night. Light rain or freezing rain will affect the area
tonight into the early morning Friday. The freezing line will be
close for the terminals, so aviation interests should be sure to
check back throughout the day Thursday. Winds will become
northeasterly and then easterly through the day Thursday.

Hydro...

The Sugar River reached major flood at Albany and will approach
major flood at Brodhead.

PREV DISCUSSION... (Issued 230 AM CST Thu Feb 22 2018)

DISCUSSION...

Today and Tonight...Forecast Confidence is Medium...

A receding high shifts northeast into southern Canada, away from
the western Great Lakes on Thursday. One upper jet max moves off
as a second moves toward southern Wisconsin. Upper level
divergence and 700 mb upward motion increases. Low levels are dry
and slower to moisten, as 700 mb layers saturate.

As a result much of today is looking dry across southern WI as
dry easterly flow persists through the day. Deeper moisture from
will be pushing northward as winds become southerly ahead of
a trough of low pressure moving into Wisconsin. Some light
precipitation may reach southern Wisconsin, mainly west areas
this afternoon. Precipitation will tend towards snow initially,
then become a mix with freezing rain and some sleet possibly,
especially north and west areas, this evening as an inversion
causes low levels to warm.

Expect glazing of 0.01 to 0.10 inch and may affect the Friday
morning early morning commute. A Winter Weather Advisory has been
issued for Tonight, except southeast.

Friday - Confidence...Medium
Low pressure will lift northeast from central WI. The bulk of the
precipitation will be across ne WI in the morning. Progs suggest
parts of the cwa will see some of this linger in our area during
the morning with the bulk of it in the northeast cwa. Should be
mostly rain though some patchy light freezing rain not out of the
question. The afternoon looks dry with only weak cold air
advection expected.

Saturday and Sunday - Confidence...Medium to High
Strong negative tilt shortwave will lift northeast through the
state Saturday night. Pronounced push of warm air with 850
southerly jet. Surface/850 low track to our northwest favoring the
warm solution for our area. Highest pops and warmest profiles will
be Saturday evening prior to 06z, when DCVA is maximized/thermal
ridge axis peaks with the approaching shortwave. Later Saturday
night after the low lifts further northeast colder air will wrap
in on very gusty west/southwest winds. May see wind advisory
conditions based on wind profiles on GFS soundings. We may see a
light mix for a time prior to 12z. Deeper mixing may sustain wind
advisory conditions for a time into Sunday.

Monday and Tuesday - Confidence...Medium
Looks like a dry period with modifying thermal profiles. A return
southerly flow will be responsible as a new low pressure system
takes shape in the central Plains.

Tuesday night and Wednesday - Confidence...Low to Medium
Likely to se an uptick in precip chances this period though GFS
and ECMWF show differing solutions. The ECMWF sends a weak trough
towards our area with a period of light rain possible. Meanwhile
the GFS develops a stronger low and tracks it to our south and
southeast by later in this period and beyond. Looks like rain
would be a good bet initially in this scenario with some
changeover potential if this stronger low and colder track plays
out especially just beyond this period.

AVIATION(09Z TAFS)...VFR will prevail into the afternoon hours,
before ceilings begin to lower in response to an approaching
trough. Expect to see ceilings fall into MVFR tomorrow afternoon,
and then eventually IFR late Thursday night. Light rain or
freezing rain will affect the area tonight into the early morning
Friday. The freezing line will be close for the terminals, so
aviation interests should be sure to check back throughout the day
Thursday. Winds will become northeasterly and then easterly
through the day Thursday.

MARINE...Northeast winds will become easterly and increase on
Thursday. Waves will increase as well, with 3-5 ft waves Thursday
afternoon building to 4-7 feet Thursday night. A Small Craft
Advisory is in effect.

Winds will become westerly behind the trough Friday, before
becoming easterly to southeasterly once again late Saturday into
Sunday. There are indications that strong low pressure may move
through the Great Lakes region Sunday, with increasing winds and
waves in response.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 6 PM this evening to 6 AM CST
     Friday for WIZ046-047-056-057-062-067.

     Winter Weather Advisory from 9 PM this evening to 6 AM CST
     Friday for WIZ051-052-058-059-063-064.

LM...Small Craft Advisory from 3 PM this afternoon to 8 AM CST Friday
     for LMZ645-646.

     Small Craft Advisory from 6 PM this evening to 8 AM CST Friday
     for LMZ643-644.

&&

$$

Update...Gagan
Today/Tonight and Aviation/Marine...Gagan
Friday THROUGH Wednesday...Collar



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