Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 240400 AAB

Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1100 PM CDT Fri Mar 23 2018

Issued at 709 PM CDT Fri Mar 23 2018

The forecast is in pretty good shape. 22Z RAP/HRRR have shifted
north substantially from prior runs and are now closer to the
global guidance. This has increased confidence markedly in where
the gradient should ultimately set up overnight. A developing
rain shield across northwest Iowa into southeastern South Dakota
will continue to blossom this evening as it slowly builds
northeast into western and southern Minnesota. Some scattered
thunderstorms are also embedded within these showers. Thunderstorm
activity should wane as the activity lifts northward. Expecting a
prolonged period of heavy snow across the warned areas into
Saturday morning with 1 to 2 inch per hour rates at times as the
precip shield reaches maturity. QPF on the hi-res guidance is
really impressive but not too surprising given the moisture and
dynamics in play, time of year, and their bias toward higher
values overall. Not buying into the patches of 1.5 inch QPF yet,
but even if some of that is partially true we`d see several 10
inch totals. Blended in some of that QPF into the forecast to
tighten the gradient even more on the northeast fringe and to beef
up the totals a bit across the south. This brought snow totals
more into the 8 to 11 inch range across most of the Minnesota
River Valley east of Montevideo.


.SHORT TERM...(This evening through Saturday)
Issued at 351 PM CDT Fri Mar 23 2018

The drier and cooler air mass that was centered over Hudson Bay this
afternoon, has kept the persistent dry easterly flow across most of
the Upper Midwest. Thus, all the precipitation has nearly dissipated
as it moved eastward into Minnesota since this morning.

Earlier today, we delayed the onset of the precipitation a few
hours, but at the same time, models continued to support a drier
trend, and thus, limiting the amount of precipitation to the east,
holding off the initial start, and overall amounts. Therefore,
several of the counties along the eastern edge of this storm have
been either downgraded to an advisory, or have been cancelled. Only
areas along the Minnesota River Valley, and southward to the Iowa
border, will still see the bulk of the heavy snowfall overnight,
through Saturday morning.

The main feature of interest this afternoon was moving out of the
central Rockies. Bands of showers have already developed over
northern Nebraska in response to the increasing lift with the upper
energy. These showers will move northeast into South Dakota this
evening, and into far western Minnesota after 9 pm, before changing
over to all snow toward midnight.

As discussed earlier, the persistent dry easterly flow will play
havoc for the onset of precipitation in central, and east central
Minnesota. This area may not see any precipitation until Saturday
morning. The best location of both moisture availability and jet
energy, will occur along the Iowa border toward midnight. This is
where some of the HIRES models indicated a heavier band of
precipitation developing.

Eventually, which coincides with increasing moisture, and jet
energy, areas south and east of a line from Montevideo to Mankato,
and Albert Lea will see locally heavy snowfall toward midnight. A
period of moderate, or occasional heavy snowfall is likely in this
area before tapering off toward 9 am. Localized 9-10 inches of snow
could fall in far southern Minnesota, especially along the I-90
corridor. Later shifts will need to evaluate on how strong the short
wave evolves overnight, and whether snowfall rates beginning to
increase further. The highest weather impacts will occur near the
Iowa border after midnight. By noon, most of the precipitation will
have ended from north to south, with lingering flurries possible
along the Iowa border through the afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 351 PM CDT Fri Mar 23 2018

Ridging aloft dominates on Sunday with dry conditions expected.
Southeasterly flow at the surface will allow temperatures will
rise into the upper 40s across eastern MN & west-central WI, with
areas seeing the heaviest snowfall from the Friday/Saturday system
struggling to warm past the mid-30s.

The main forecast concern in the long term will be associated
with a system approaching from the southwest on Monday. Warm
advection & plenty of isentropic ascent will generate a broad
swath of precip during the day on Monday. Will likely see a
diurnal pattern with regard to precip types with forecast
soundings supporting light snow & potentially some freezing
drizzle across SW MN during the morning. Mixed precip should
transition fully over to rain as temperatures warm during the day
with another changeover to a rain/snow mix possible again as
temperatures cool at night. Total precip amounts look to be on the
order of 0.25-0.5" with the heaviest amounts falling along the
MN/IA border.

A fairly quiet pattern dominates for the rest of the week under
west/northwest flow aloft & temperatures near average for the end
of March.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1100 PM CDT Fri Mar 23 2018

Moderate to heavy snow is developing across southern and western
Minnesota late this evening. Even a few thunderstorms have
developed across far southern Minnesota. The snow should miss STC
and MSP, but a few flurries are still possible there. LIFR
conditions are expected overnight through much of Saturday morning
at RWF and MKT. VFR at RNH and EAU.

KMSP...Could see a couple flurries overnight, but no accumulations
are expected.

SUN...VFR. Wind SE 10-15 kts.
MON...MVFR with CHC -SN in the morning, then RA. Wind SE 10 kts.
TUE...VFR with CHC MVFR/-RA. Wind NW 10 kts.


MN...Winter Weather Advisory until 10 AM CDT Saturday for MNZ041-048.

     Winter Weather Advisory until 10 AM CDT Saturday for MNZ042-049-

     Winter Storm Warning until 10 AM CDT Saturday for MNZ047-054>058-



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