Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 270006
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
606 PM CST Sun Feb 26 2017

.UPDATE...

A low amplitude shortwave trough will progress from Lake Superior
this evening into southern Ontario and Quebec later tonight.
Associated weak surface troughing now over northern Wisconsin will
depart, as rising heights aloft support surface ridging flexing
west into southern Wisconsin from the Mid Atlantic states. Brisk
winds will dissipate shortly as the pressure gradient relaxes.

An upstream area of low to mid-level clouds over the Dakotas was
occurring within a weak warm advection regime aloft, and should
continue their eastward progression overnight. Model RH fields
suggest the better coverage late tonight towards morning will be
across northern and central Wisconsin, though we may see some of
these clouds around towards morning as well.

Patchy fog is possible overnight as light winds combine with some
lingering low-level moisture below a moderately strong surface
temperature inversion. Meso model solutions are somewhat
inconsistent with visibility trends overnight, leading to some
uncertainty. Will maintain patchy fog wording in the forecast
grids overnight.

Low amplitude ridge remains in place on Monday, although it begins
to weaken by evening as shortwave energy ejects into the Great
Plains. Surface ridge remains in place, with low to mid-level warm
advection resulting in high temperatures a few degrees warmer than
today. Not bad for late February.

&&

.AVIATION/06Z TAFS/...

Brisk winds and remaining 5-6 kft cumulus will quickly dissipate
within the next hour. Light winds combined with some lingering
low-level moisture could result in patchy fog late tonight into
tomorrow morning. Confidence in this occurring isn`t particularly
high, so didn`t introduce any visibility reductions in the TAFs
just yet. If fog does develop, it will take until late morning to
scatter out. Look for light southerly winds on Monday with some
mid-level clouds.

&&

.MARINE...

The Small Craft Advisory remains in effect until 9 PM. Thereafter,
winds and waves will subside on Monday. Easterly winds will build
somewhat higher waves on Tuesday, but winds and waves are expected
to remain below Small Craft advisory levels.

&&

.PREV DISCUSSION... /Issued 328 PM CST Sun Feb 26 2017/

SHORT TERM...

TONIGHT AND MONDAY... Forecast confidence is high.

Westerly winds will diminish this evening as weak high pressure
moves overhead. Clear skies will allow temps to fall into the lower
20s tonight. Dewpoints got up to the mid/upper 20s today, so there
is a risk of some patchy fog overnight.

Light southerly winds will keep temperatures mild on Monday, with
highs in the mid to upper 40s. Leaned toward higher side of guidance
for temps using bias-corrected MOS blend.

MONDAY NIGHT THROUGH WEDNESDAY...Forecast Confidence...Medium

Models are in decent agreement showing two weak mid level
shortwaves in the southwest flow Monday night and Tuesday, as one
Jet max pushes across the Great lakes, while a second one is
associated with the advancing mid/upper trough that reaches the
upper Mississippi Valley. The ECMWF is a little slower and
stronger with the mid trough.

Should see some precipitation arrive by later Monday night ahead
of the low. Temperatures will be warming aloft and at the surface
as the precip moves in. Should see enough warming by the time the
precipitation arrives for rain. There is a little elevated CAPE
Monday night that could bring a few thunderstorms with the
low/mid level warm air advection. Looks plenty mild enough by
daybreak Tue morning for all rain. Despite the clouds and rain,
it should be a mild day inland, as southeast low level flow ahead
of the low continues to draw up warmer temps.

Thunderstorm chances Tuesday depend on the model differences, and
would increase if the more northern track low of the GFS is
correct. However even the more southern track ECMWF brings the
low across the far southeast, and would result in a chance of
thunderstorms, since it is slower and stronger.

As the low strengthens to the east Wednesday, we may see
a rain/snow mix that may chance over to snow. The slower and
stronger ECMWF brings a little more snow potential towards
Wednesday afternoon. The new ECMWF would also extend the snow
chance into Wednesday evening.

LONG TERM...

THURSDAY THROUGH SATURDAY...Forecast Confidence...Medium

Could see a little snow Thursday as a weak shortwave and
associated surface trough moves through. Looks like a dusting to
an inch, depending on the model.

Decent agreement among models for Friday, showing high pressure
and near normal temps to end the week.

GFS and DGEX show a little light snow Friday night into Saturday
morning due to warm advection as the high departs. The ECMWF has
similar warming, though remains dry. Should see above normal high
temps per latest guidance, as temps aloft are expected to continue
warming through the day.

SUnday...Forecast Confidence...Medium

The zonal mid/upper flow becomes a little more southwest as a
shortwave exits the northern Rockies. The ECMWF is a little faster
with this resulting in a little quicker return with milder air
ahead of a developing warm front across Iowa and Northern
Illinois.

AVIATION/00Z TAFS/...

Winds will diminish quickly this evening. Light winds and lingering
low level moisture will give us a chance for at least patchy fog
overnight. If fog develops it will take until late morning for the
associated clouds to clear.  Light southerly winds and a few mid
level clouds Monday afternoon will allow for mild temperatures once
again.

MARINE...

Gusty southwesterly winds will quickly diminish this evening. Gusts
peaked early this afternoon and are coming down, so downgraded the
gale warning to a small craft advisory. The advy goes until 9 pm.

Plan on light southerly winds Monday, then easterly winds will build
higher waves on Tuesday. Winds and waves are expected to remain
below small craft advisory levels.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 9 PM CST this evening for LMZ643>646.

&&

$$

UPDATE...SPM
TONIGHT/Monday AND AVIATION/MARINE...MRC
Monday NIGHT THROUGH Sunday...Hentz


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