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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
1118 am CST Tuesday Mar 3 2015

Short term...(today and tonight)
issued at 342 am CST Tuesday Mar 3 2015

Overall...confidence has improved somewhat with the evolution of the
system impacting the region today but some of the fine scale details
have yet to come into complete focus due to some consistency issues
in the hourly hrrr/rap guidance. The band of snow over west central
Minnesota is indeed forming quickly early this morning in response to a
ribbon of strong forcing with the middle level shearing
vorticity/frontogenesis. The band is expected to be anchored there
for much of the morning and will bring 3 to 5 inches of snow from
west central to northeast Minnesota. A second band is showing some
beginning signs of development across northern Iowa due to middle/upper
level forcing on the northern periphery of the upper jet. This band
should also bring an enhanced area of snowfall from southeast Minnesota
into central WI. The area in between...from southwest Minnesota to west
central WI will remain dry until dawn or shortly thereafter before a
consolidation of the two areas of forcing begin and the surface low
tracks to the south. Widespread snow will then occur for a 3-4 hour
window this morning before the front drives the snow east by early
afternoon. Due to the brief period of snowfall...not expecting too
much accumulation from southwestern/sctrl Minnesota to wctrl WI - maybe around two
inches. This is the area plagued most with uncertainty.

How much falls will strongly determine how far east blizzard
conditions will reach this afternoon. There isn/T much snow on the
ground now across the northeastern half of the Blizzard Warning.
However...the snow will be falling during a period of light winds
ahead of the front which will enhance the snow ratio. The powdery
nature of the snow followed by a very rapid ramp up of the Post
frontal winds could still lead to whiteout conditions. Would prefer
to see 3 or 4 inches on the ground...but it is not unheard of to
have blizzard conditions with just one or two...particularly if it
had just fallen. Although there are some reservations with how far
east the warning extends...will not cancel yet and await the
development of the snow. The counties most likely to be dropped
would be Meeker...McLeod...Sibley...and Le Sueur.

The wind grids still look good with a swath of sustained 25-30 knots
and 40+ knots gusts along and south of the Minnesota river early this
afternoon.

Winds will ease this evening as more Arctic air spills south. Lows
in the single digits below zero look like a slam dunk with some
teens below possible in wctrl Minnesota. Some wind chills will drop colder
than 25 below over central and western Minnesota...but will wait for current
headlines to be cancelled before issuing any wind chill
advisories.

Long term...(wednesday through monday)
issued at 342 am CST Tuesday Mar 3 2015

The long term concerns are the development of warming trend late
in the week and through the weekend.

Initial cold shot following tuesdays system will leave below normal
readings to the area through Thursday. Will have wind chill
concerns over the west portion of the County Warning Area late tonight into
Wednesday morning...with wind chill values dropping to 25 to 30
below. Winds are expected to remain breezy through Wednesday as
the Arctic air settles into the region. Trough extension over
northeast Minnesota will drop cold pool of air over the eastern area
during the day Wednesday. Clouds are expected to develop into
Wednesday afternoon as the trough moves across mainly west central
Wisconsin. We could see a few flurries with this feature as
well...but limited that to the far northeast periphery of the area
for now.

The large high pressure area drops south over the central Continental U.S. For
Wednesday night/Thursday morning. This will leave lighter winds but
colder temperatures for the area. Readings may not be cold enough
over the fresh snow covered areas. Will have to monitor what
verifies for Tuesday. Wind chills will have to monitored
again...but do expect winds to be much lighter.

The deterministic models then trend toward building heights and less
amplified flow pattern over the Continental U.S. With large upper ridge
becoming established over the western Continental U.S. Into the weekend. This
will leave the area vulnerable to brief cold front intrusions but
timing of any impulses that ride across the northeast portion of the
area is difficult. Carried the slight chance probability of precipitation in the guidance
for Sunday as this appears to greatest threat of a more significant
cold frontal passage.

The latest cfs ensemble plumes were showing a warming trend lasting
until at least the middle of the month. This verifies the
deterministic long term models with the European model (ecmwf) most bullish with the
higher heights/warmer temperatures. The cips extended analog threat
guidance takes US all the way through middle month...and is showing
high probability of above normal temperatures and relatively dry
conditions. For the moment...we did warm temperatures from extended
guidance quite a bit. If the European model (ecmwf) verifies...we could be seeing
temperatures warming through the 40s and into some lower 50s for
parts of the area...early next week.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1115 am CST Tuesday Mar 3 2015

Last band of moderate/heavy snowfall in far eastern Minnesota...moving toward
the east-northeast at 45 kts late this morning. Some residual light snow is
evident behind the main bands in central Minnesota...but believe this is
more flurry activity with visibilities of 3-5sm. There is some convective
type reflectivity enhancement noted in far western Minnesota/eastern South Dakota
on regional radar where some localized snow showers will be
possible during the afternoon. This should also enhance the IFR visibility
in blsn in wc/SW/SC Minnesota. Confidence remains moderate with 1sm in
blsn at kaxn/krwf with a temporary period of 1/4sm blsn at krwf
due to the strong winds and some snsh. Elsewhere...strong northwest winds
will develop with some areas of 4-6sm in blsn. Conds should
improve this evening with gusty winds diminishing. No other
aviation concerns past 3z.

Kmsp...

By 18z...only -sn is possible for an hour with more blsn reducing
visibilities temporary to 4-6sm through 1z. Otherwise...ceilings will lift to
VFR but strong northwest winds will develop. Expect winds of 18-22 kts by
middle afternoon with gusts up to 30 kts at times. These winds will
diminish this evening...but redevelop Wednesday afternoon along with
some MVFR ceilings. High confidence of visibilities becoming MVFR/VFR this
afternoon. Lower confidence on MVFR ceilings.

/Outlook for kmsp/

Wednesday nght...VFR. Winds west-northwest 10 kts.
Thursday...VFR. Winds SW 5-10 kts.
Friday...VFR. Winds west 5-10 knots.

&&

Mpx watches/warnings/advisories...
Minnesota...Blizzard Warning until 9 PM CST this evening for mnz047-048-
054>058-064>067-073>076-082>085-091>093.

Winter Weather Advisory until 9 PM CST this evening for
mnz041>045-049>053-059>063-068>070-077-078.

WI...Winter Weather Advisory until 9 PM CST this evening for
wiz014>016-023>028.

&&

$$

Short term...borghoff
long term...dwe
aviation...jlt

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