Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1107 PM CDT Sat Mar 15 2014
Short term...(this evening through sunday)
issued at 323 PM CDT Sat Mar 15 2014
Another quiet period in the short term as the upper Mississippi
River valley finds itself sandwiched between two systems. The
first is a 1008mb surface low that as of early this afternoon
was located along the NE/Kansas border. This low will propagate
southeast today...with a band of heavy snow expected to develop
across central Iowa. Meanwhile a weak Lee side low will develop in
Alberta...and this will create southeasterly winds over the High
Plains. Minnesota/WI will lie in between these two systems...and as a
result the winds will go calm and low temperatures will drop below
zero across the St Croix River Valley and points eastward.
Temperatures will moderate Sunday as southeasterly flow develops
ahead of the aforementioned Lee side low. No precipitation is
Long term...(sunday night through saturday)
issued at 323 PM CDT Sat Mar 15 2014
Attention will be most focused on the incoming prolonged winter
storm system expected to impact the weather forecast office mpx County warning forecast area Monday night through
To start...a weak clipper-type system will drop into the region
from central Manitoba Sun night into Monday. This compact system will
remain mostly in Canada...but a southward extending trough will sweep through
northern and central Minnesota...possibly bringing some -sn with it for northern
and western portions of the County warning forecast area. Little to no snow accumulate is expected
with this system.
However...what this weak system will do on its backside is allow
for surface winds to become southerly and upper level flow to become more
zonal...even slightly SW. These shifts will allow noticeably
warmer air to infiltrate the region not only at the surface but through
the blyr ahead of the more potent system for the first half of the
week. This warmer air will be felt on Monday as highs in western through
southern Minnesota hit the lower 50s and possibly even near 60 in far southwestern Minnesota.
This warm air intrusion...where it sets up depending on the track
of the system...will be a major player in determining p-type for
much of the County warning forecast area. Precipitation will move into the region Monday
night...starting out as liquid -ra for the area. However...as the
system treks across southern/central Minnesota and colder surface air is dragged
down from Canada on its backside...the warmer air aloft will aid
in transitioning the precipitation to a mixture of -zr and
-ip...especially -zr going into the Tuesday morning rush hours
timeframe for much of central Minnesota...including the Twin Cities
metropolitan. Still too early to determine how much icing would be
expected but with liquid quantitative precipitation forecast in the 0.10-0.15 area...it would not
be unreasonable for potentially up to a tenth of an inch of ice to
develop over central/eastern Minnesota. There will then be additional changes
in p-type all across the County warning forecast area as the warmer air expands near the surface
in southwestern portions of the County warning forecast area while the colder air deepens in northwestern
portions...so there will be gradients developing of
-ra/-fzra/-ip/-sn across the area during the day on Tuesday. This system
gradually wraps up within itself and rotates away Tuesday night into
Wednesday as a digging upper level trough picks up the system...ending any
remaining warm air advection and allowing deeper cold air advection to move into
the region. This would then force any remaining icy/liquid precipitation
to transition to -sn...thus the best chances for accumulating snow
would come late Tuesday night through Wednesday before the system exits. Snow
amounts will again have a sharp gradient as 5-9 inches is expected
over northern Minnesota with amounts dropping significantly going southward.
So...attm...it looks like northern portions of the mpx County warning forecast area would see
up to around 3 inches...and nearly an inch in the Twin Cities metropolitan
and Eau Claire...with little-to-no accumulations near the Iowa
border. But...again...the caveat that even minor changes in the
track can have significant ramifications with snow amounts.
This system will exit the area by late Wednesday...allowing for high
pressure to Glide across the region Wednesday night into Thursday. However...
following for Thursday night into Friday will be another winter storm
system that will bring more mixed precipitation to the region.
So...overall...certainly an active pattern that deserves much
attention and may well result in multiple changes to the forecast.
Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1101 PM CDT Sat Mar 15 2014
No big changes to the previously issued 00z taf. Northern and
portions of central Minnesota should get a little light snow near the end
of the taf period...so this was mentioned at kaxn...but not
included at other taf sites. High confidence in VFR conditions
over the next 24 hours otherwise.
We pushed back the timing of the NE to southeast wind shift...but no big
changes to the taf otherwise. The radar scope could show light snow
well north of the Airport Sunday night...but just expect
increasing middle-high clouds at kmsp. VFR is expected. The weather
should turn more active late Monday through Wednesday.
/Outlook for kmsp/
Monday...VFR with MVFR and -ra possible late. Winds S at 10g15kts.
Tuesday...MVFR with IFR and -sn/ra/fzra possible. Winds NE at
Wednesday...MVFR with IFR and snow possible early...then VFR.
Winds northwest at 20g30kts.