Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1047 PM CDT Tuesday Mar 31 2015
Short term...(this evening through wednesday)
issued at 325 PM CDT Tuesday Mar 31 2015
The primary concern in the short term period will be thunderstorm
development and intensity on Wednesday afternoon and strong winds as
a cold front approaches the area.
In the meantime...tonight will bring a gradual increase in middle/high
clouds and strengthening winds as the warm front associated with the
low pressure system lifts into southwestern Minnesota. Temperatures
over the Minnesota River Valley should plateau after midnight...and remain
nearly steady as southerly winds increase ahead of the front.
By late morning Wednesday...BUFKIT profiles indicate winds along and
south of the Minnesota River Valley have the potential to reach sustained
speeds of 30 to 35 miles per hour...with gusts into the 40s. Have therefore
issued a Wind Advisory for much of west and south central Minnesota.
Moisture pooling/advection ahead of the front are expected to keep
relative humidity values in check /as also illustrated by the
forecast soundings/...which will minimize fire weather concerns on
Wednesday even though the winds will be strong.
As the front arrives...several of the hi-res models appear to be
depicting development in a reasonable manner...with a SW-NE oriented
line of showers and thunderstorms developing from southwest Minnesota to
the Twin Cities to Rice Lake Wisconsin between 21z Wednesday and 00z Thursday.
As far as the potential for severe storms is concerned...still looks
like the primary area would be southern Minnesota where the opportunity for
surface-based convection is greater.
Long term...(wednesday night through tuesday)
issued at 315 PM CDT Tuesday Mar 31 2015
Timing of the cold front across the eastern County Warning Area is the main
concern initially. Then fire weather and wind concerns develop
Slower movement of the cold front into the evening looks justified
as the upper trough swings east across the County Warning Area. Will use a
compromise NAM/European model (ecmwf) solution...as the GFS appears too fast into
Wednesday evening. Instability becomes shunted south as the front
makes progress east into the evening and should see thunder
threat trail off through 06z Thursday. Still have some 0.25 to 0.50
inch quantitative precipitation forecast amounts over the eastern County Warning Area through the evening.
Cooler and drier conditions develop through Thursday
morning...with strong pressure rises building into the western County Warning Area
through late morning/afternoon. This should increase
west/northwest winds in the wake of the front...with some gusts
35-40 miles per hour once again. This along with the drier air moving
in...and decent mix of the boundary layer will yield some lower
humidity values during the afternoon...especially across the
Minnesota County Warning Area. Will have to monitor for critical fire weather day
The long term models are in fair agreement into weekend...with
cooler and drier conditions. Still see some chance of a mixed
light rain/snow event over the area Sunday and Sunday night. The
western trough moves ashore with brief riding into the
weekend...but the main baroclinic zone remains across the central
Continental U.S. Into early next week. The area remains on the cooler side of
this zone...with below normal temperatures developing along with
increasing threat of rain into early next week as the
trough/surface low pressure system moves across the Central
Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1047 PM CDT Tuesday Mar 31 2015
Southeast winds will be in the increase overnight with strong southerly
winds developing Wednesday morning. Sites most impacted by the winds on
Wednesday are krwf and kmsp. NAM solution this evening was a tad slower
on the rain showers/thunderstorms and rain development Wednesday afternoon with the timing adjusted
by an hour or two. An initial broken line of convection should
develop from near krwf to east of kstc around 22z...spread across
kmsp and krnh in the 23z-01z time frame and into Keau after 02z.
Winds will be shifting to the west-northwest Wednesday night as a cold front pushes
Kmsp...strongest southerly winds on Wednesday still indicated from
18z-22z with 24g33kt forecast. Thunderstorms and rain chances highest in the 23z-01z
period with rain showers from 01z-03z. Winds shifting northwest after
/Outlook for kmsp/
Thursday...VFR. Winds northwest 10 kts in the morning becoming west 20g35 kts in the afternoon.
Friday...VFR. Winds northwest 10-15 kts.
Sat...VFR. Winds west 10-15 kts.
Minnesota...Fire Weather Watch from 10 am CDT Wednesday through Wednesday
evening for mnz076>078-083>085-091>093.
Wind Advisory from 9 am to 5 PM CDT Wednesday for mnz064-065-067-