Area Forecast Discussion
Issued by NWS Twin Cities, MN

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927
FXUS63 KMPX 170527
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1127 PM CST Mon Jan 16 2017

.UPDATE...
Issued at 1115 PM CST Mon Jan 16 2017

Updated to include 06z aviation discussion below.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 334 PM CST Mon Jan 16 2017

Precipitation, mainly light freezing rain, has been advancing/
developing northward through south central MN and adjoining areas
of western WI at near 20 knots through mid afternoon. The hourly
HRRR simulated radar forecasts have had a good handle on this
northward advancement. The northward advancement is expected to
end early this evening along a line from Redwood Falls through the
south Metro to near Cornell in west central WI with a more
eastward push there after. This is about the farthest north of any
of the solutions today, with quite a few deterministic/CAMS
stopping in Scott and Dakota counties early this evening. We added
a few counties to the winter weather advisory late this morning
based on earlier HRRR runs and this still looks good at this
point.

Surface temperatures have reached the freezing mark at mid
afternoon along the I-35 corridor from Albert Lea to Owatonna and
Waseca, helping to mitigate ice accumulation. It`s areas to the
west, north and northeast toward Eau Claire where icing is a
concern for travel over the next 3 to 4 hours. But even in these
areas, temperatures will likely rise to around freezing with even
some rain indicated with the HRRR. Once the system begins to
translate eastward this evening, (8-9PM), there will be a
changeover the snow and sleet and then to all snow. The best
corridor for snow accumulation during the late evening and early
morning hours on Tuesday stretches from St. James and Fairmont on
northeast through Eau Claire and Cornell with around an inch to an
inch and a half forecast.

A concern late in the night is that we will lose the ice in the
clouds but still have a saturated low level profile. Light
northwest surface winds will back to the northeast a few hundred
feet up along with increasing speed. This is a good situation for
freezing drizzle and we incorporated this into the late night
forecast.

Tuesday will be a somewhat better day weatherwise with the system
having departed off to the east. We will still have to deal with
considerable clouds early on. An issue that will need to be
watched is the threat for dense fog due to the light winds and
near surface saturation. Areas of central minnesota seem most at
risk for dense fog by daybreak.

Quite a range in lows tonight due to the differences in cloud
cover/precip across the FA with lows ranging from the single
digits above zero in Alexandria to around 30 for the Twin Cities
on east and south. Quite a range on Highs for Tuesday as well with
25 to 30 for western MN with 30 to 35 for eastern MN and western
WI.

.LONG TERM...(Tuesday night through Monday)
Issued at 334 PM CST Mon Jan 16 2017

The January thaw will commence this week, and last through the
weekend before some modification to the mean temperatures next week.

First, the positive long wave trough that has allowed for tonight`s
system to move from the desert southwest, into the Plains, and
eventually into the northeast, will be followed by another upper low
moving out into the Plains late this week.  Depending upon a
developing upper ridge over the Great Lakes which strengthens or
moves northward this weekend, will be dependent on the next upper
low movement across the Plains early next week.

Secondly, both the GFS/EC favor the southern jet stream energy
through this week, and into early next week. This will keep the bulk
of the significant weather across the central/southern Plains, and
into the Midwest. The northern jet stream will be concentrated in
Canada through Thursday allowing for wet/stormy weather for the
Pacific Northwest, and western Canada. However, the long wave
pattern becomes more problematic late in the week, and into the
weekend as a long wave trough and associated unsettled weather moves
further south across the western U.S..  Eventually the western U.S.
will become more active which has been the case this winter.

For our region, other than a weak system late Friday/early Saturday,
the bulk of the week will remain dry and unseasonably mild. With the
snow pack across Minnesota and western Wisconsin expected to slowly
melt, the forecast challenge would be fog and low cloud development,
and minimal diurnal temperature swings from overnight lows and
daytime highs. The forecast highs/lows this week and into the
weekend have been modified some for a milder outcome. I would not be
surprised to see a period where the temperatures in southern
Minnesota do not fall below freezing for a couple of days.

As with the previous forecast elaborated on record high/low
potential later this week, and into early next week, I wouldn`t be
surprised to see highs approaching records, but due to the snow pack
and low sun angle, it doesn`t seem likely. There is a better
potential of overnight lows not dropping before freezing. Therefore,
record low maximums could be in jeopardy.

The longer range past the next 7 days does support more seasonable
temepratures which are highs in the 20s and lows around 10-15
degrees. As the transition of more seasonable temperatures and an
active weather pattern developing next week, additional snowfall
becomes more likely.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1115 PM CST Mon Jan 16 2017

MSP and both WI sites still dealing with mainly -FZRA (and some
-RA mixed in) while the remaining MN TAF sites are dealing with
fog and low stratus. The precipitation shield has slowed its
eastward progress so have reflected this thinking in the 17/06z
TAFs plus to advertise FZRA as the primary p-type with -SN
possible during the early morning hours. By daybreak, much if not
all of the precipitation should be east of all TAFs but low
stratus and low visibilities will likely prevail through daybreak.
Improvement will be slow to come by during the day Tuesday but VFR
conditions are expected by late afternoon. Winds will generally
remain 5 knots or less as they gradually shift from north to
southwest.

KMSP...Sustained FZRA to persist over KMSP for at least another
2-3 hours before becoming more intermittent going into the early
morning hours. Precipitation expected to shift off to the east for
the Tuesday morning push but there is still a chance for some FZDZ
to develop behind the main exiting swath of precipitation. Even if
no additional precipitation develops, low IFR ceilings and MVFR-
IFR visibilities are likely through daybreak with slow improvement
during the day.

/OUTLOOK FOR KMSP/
Wed...VFR. Winds SW 5-10 kts.
Thu...VFR. Winds S 5-10 kts.
Fri...VFR. Slight chance of MVFR and -RA. Winds southeast around 5
mph.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 AM CST Tuesday for WIZ023>028.

MN...Winter Weather Advisory until 6 AM CST Tuesday for MNZ060-062-
     063-066>070-074>078-082>085-091>093.

&&

$$

UPDATE...JPC
SHORT TERM...RAH
LONG TERM...JLT
AVIATION...JPC



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