Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1247 PM CDT Monday Mar 10 2014
Short term...(today and tonight)
issued at 458 am CDT Monday Mar 10 2014
The snow event for southern Minnesota is still on track for Tuesday
morning...but conditions are looking less promising for anything
more than 1-2" of wet snow. Most locations that see snow will end up
with little to no accumulation - perhaps a little slush on roads and
Besides the trough moving into the Pacific northwest this morning
and the closed low over western Mexico...most of North America is
being influenced by a low amplitude long wave ridge...a ridge that
is bringing mild temperatures to many areas in the northern Continental U.S.
That have seen well below normal the past 60-90 days. High
temperatures underachieved a little yesterday in part due to the
cold start /teens/...but also due to the overcast skies that moved
in during the morning - we thought there would be more filtered
sunshine. Today...we will definitely see a little more sunshine and
Minnesota/WI is starting off 20-25 degrees warmer as well. So...50 degrees
is only 10-15 away at this hour. This should be achievable with a
light west-SW flow. The wind should switch to the west-northwest during the
afternoon and cold advection will likely slow our warming as a
result. Besides sunday's temperatures...the last time we got into the upper
40s locally was on Dec. 28. Kmsp hit 47. We were near our solar
minimum on that day...skies were partly to mostly cloudy...and the
winds were southeast. So...given the current 925-850mb temperatures...lack
of clouds at this hour...W-SW winds...and strong March sun - i'd be
surprised if many more sites didn't hit 50 today.
The European model (ecmwf) remains the northern-most of the model solutions with the
quantitative precipitation forecast early Tuesday and the NAM is the southern-most. As has been the
case over the past day or so...the GFS splits the distance between
the NAM and European model (ecmwf). The rain-to-snow transition should happen fairly
fast late tonight once the precipitation begins. The expected temperature
sounding doesn't have to cool much to change over to all snow for a
few hours before ending middle-to-late Tuesday morning. The snow ratio
will not be high given the expected wet/slushy nature to the snow.
The good lift and upward motion and stickiness of the expected snow
show make for large snow aggregates or large flakes. The surface
temperature will be near freezing though...so accumulation will be hard to
Long term...(tuesday through sunday)
issued at 458 am CDT Monday Mar 10 2014
At the start of the period an area of snow will be ongoing south of
the County Warning Area. Another system will move across the north Wednesday
night...with a stronger system on track for Friday. The precipitation
associated with fridays system will be mainly across the US/Canada
border. Temperatures will range from near normal on the warm side of
these waves...to roughly 10 to 15 degrees below normal on the cold
On Tuesday night the system that brought a rain/snow mix across the
south will quickly organize into a full-fledged cyclone over the
eastern Continental U.S.. meanwhile a weak northern stream shortwave will slide
down along the Red River valley and bring a chance for a few light
snow showers or flurries early Wednesday morning. Late Wednesday
night warm air advection will develop across the region and bring
another chance of light snow across the St Croix River Valley. By
Thursday southwest flow bring another round of warm air. The timing
of the thermal ridge together with the southwest winds will allow
the maximum heating to be realized...but the magnitude of warm air
should keep temperatures from getting out of control as h925 temperatures
range from around 0 near the Minnesota/WI border to near 10c across the
Buffalo Ridge in southwest Minnesota. Currently going with the higher end
of guidance...but may need to adjust these temperatures upwards depending
on the model trends.
Looking ahead...the clipper system responsible for this warm up will
bring snow across the international border...and another round of
cool temperatures for the weekend. No significant precipitation is
expected through the end of the period.
Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1235 PM CDT Monday Mar 10 2014
No aviation concerns for the first 6-9 hours as dry air and high
pressure remains in control. Winds will remain from the west/northwest
under 12 kts this afternoon...becoming more northwest/north-northwest by middle/late evening
and decrease to less than 7 kts.
After 3-6z...conds will likely deteriorate across wc/SW Minnesota...and
spread east/east-southeast as a storm system moves out of The Rockies...and
into the northern plains/upper Midwest. Based on the latest model
information...ceilings will likely lower rapidly between 6-12z with
rain and/or snow developing. Have lower ceilings and visibilities based on
the latest information. Winds will increase Tuesday morning from
the north/north-northeast around 10-15 kts.
No aviation concerns through 6z with winds from the west-northwest/northwest around 8-11
kts this afternoon...decreasing this evening and becoming more north-northwest.
Between 6-12z...conds will likely deteriorate as a storm system
moves eastward. Latest information has the bulk of the heaviest
quantitative precipitation forecast amts across the Twin Cities between 9-15z. Therefore...IFR
visibilities/ceilings developing are becoming higher in the confidence
level. Later shifts will need to monitor how the radar trends are
developing across wc Minnesota. Winds will increase by middle/late Tuesday
morning from the north-northeast around 10-15 kts.
/Outlook for kmsp/
Tuesday night...becoming VFR. Northwest wind 5-15 knots.
Wednesday...VFR. Northwest wind 5-7 kts becoming west.
Thursday...VFR. West wind 5-10 kts becoming SW.