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Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota
714 PM CDT Friday Mar 27 2015

Short term...(this evening through saturday)
issued at 330 PM CDT Friday Mar 27 2015

Early afternoon water vapor imagery together with GFS 500mb heights
and winds identified a ridge across the western Continental U.S....with a deep
trough extending over the eastern half of the United States. A
subtle short wave was located in the northwest flow downstream of
the ridge axis...and this was the driving force behind an area of
light snow over the far eastern Dakotas. This precipitation matches up well
with the h700 fgen analyzed on the Storm Prediction Center mesoanalysis Page...and has
struggled to migrate eastward as it encounters the dry air on the
back side of the departing surface high.

This afternoon and evening the hires models are in good agreement
that the precipitation will gradually diminish as it slides southward. By
Saturday morning south southeast winds will increase across the
region which will lead to deeper mixing and warmer temperatures
Saturday afternoon. No precipitation is expected on Saturday.

Long term...(saturday night through friday)
issued at 330 PM CDT Friday Mar 27 2015

The main concern in the extended period is the potential of very
strong winds and heighten fire danger Sunday in southwest
Minnesota. A Fire Weather Watch has been issued for Sunday
afternoon for southwest Minnesota due to strong winds and low
humidity levels.

A potent storm system off the coast of Washington state this
afternoon is forecast to move eastward across the northern
rockies and into the northern plains/upper midweek by Sunday.
Models have been trending on a stronger and more potent shortwave
associated with this system as it moves onshore and into the
northern rockies. Differences develop on the Lee of The Rockies as
the ec and Gem have been a bit slower than the NAM/GFS. The main
differences is in the timing of the precipitation developing late
Saturday night/Sunday morning. Initially...dry atmosphere across
the Great Lakes will hinder low level moisture until precipitation
starts to develop across the Dakotas and moves eastward. A low level jet is
prognosticated to develop across western Minnesota late Saturday night leading
to better forcing in wc/central Minnesota after midnight. This is also
where the highest chance/S of precipitation and associated quantitative precipitation forecast will
occur. Across southern Minnesota...the mean dilemma for higher
precipitation chance/S is a surface trough ahead of the main cold
front Saturday night...and whether there will be precipitation
developing along it. Models place the best quantitative precipitation forecast amts along and
north of the nose of the low level jet...which is correct.
However...depending upon how the low level jet veers to the SW...may induce
further development across southern Minnesota. This would lead to a
secondary area of precipitation across south central...moving to
the northeast across southeast Minnesota/wc WI by Sunday morning.
Therefore...another area of higher quantitative precipitation forecast amts would occur in SC/southeast
Minnesota and wc WI Sunday morning.

Although all of the precipitation should be in the form of
rain...thickness values and soundings across far ec Minnesota/wc WI
remain critical enough to warrant sleet/snow and possibly freezing
rain. Based on climatology...freezing rain is not likely in
March...and the likely scenario is no freezing rain will occur.
However...the concern is the current snow cover in southeast Minnesota and the
terrain which may allow for temperatures to drop below freezing late
Saturday night. Have introduce freezing rain/sleet and snow for
these areas...but do not expect any icing problems at this time.

In the wake of the cold front Sunday...the pressure gradient
tightens /strong pressure rises/ which leads to gusty winds.
Current model guidance suggest winds gusting over 40-45 miles per hour in the
typical areas of western and southern Minnesota. A few gusts over 50 miles per hour
are also possible.

The forecast past Sunday will continue with the warming trend
with temperatures rising into the 50s/60s. Increasing thickness values
and rising 500 mb heights lean toward this scenario. As with previous
discussions...there is a chance of our first convection Wednesday
afternoon based on instability values ahead of another cold front.

Fire weather...
issued at 330 PM CDT Friday Mar 27 2015

Strong northwest winds will develop Sunday as a storm system
moves across the upper Midwest and into the Great Lakes region.
Winds will increase to 25 to 35 miles per hour by middle morning...and continue
through the afternoon. Initially... humidity levels will be above
50 percent during the morning. However...by the afternoon...humidity
levels are expected to drop below 40 percent in southwest
Minnesota. These strong winds and low humidities will combine to
create the threat for seeing critical fire weather conditions. If
further mixing develops in the lowest 5000 feet...humidity levels
could drop below 30 percent during the afternoon.

&&

Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 715 PM CDT Friday Mar 27 2015

VFR conditions expected. Middle level cloudiness will continue
through much of the night with a decreasing trend expected by
morning. Winds will remain light...but will increase and gust from
the south Saturday afternoon.

Kmsp...no additional concerns.

/Outlook for kmsp/
sun...VFR. Morning precipitation ending with clearing skies. Winds northwest 25g35kts.
Monday...MVFR possible. Winds west 5-10kts.
Tuesday...VFR. Winds light/variable becoming S 5-10kts.

&&

Mpx watches/warnings/advisories...
Minnesota...Fire Weather Watch from Sunday afternoon through Sunday evening
for mnz064-073-074-082-091.

WI...none.
&&

$$

Short term...jrb
long term...jlt
aviation...borghoff

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