Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
650 PM CDT Monday Mar 30 2015
Short term...(this evening through tuesday)
issued at 315 PM CDT Monday Mar 30 2015
Tonight and Tuesday...surface analysis shows a low pressure center
near the border triple Point of Minnesota/ND/SD while a backdoor cold
front is draped from the Minnesota arrowhead southeastward over the Great Lakes. A
weak surface trough just S of the cold front has kept east to southeast winds along
with midlvl clouds and occasional -shra over much of the
County warning forecast area...mainly along and north of the I-94 corridor. The only portion
of the County warning forecast area not subject to the cloud/precipitation complications has been
southwestern portions where temperatures have surged into the lower 70s.
Meanwhile...the vast majority of the County warning forecast area has held in the upper 40s
to middle 50s with the cooler low level conds in place. As the low pressure
center slides over the area...winds will shift around to NE then
northwest...bringing in a drier airmass to the region for overnight into
tmrw...resulting in mostly clear skies overnight through much of
tmrw. Despite the frontal passage passage creating upper level northwesterly flow...the
large upper level ridging over the western Continental U.S. Will shift into the
central Continental U.S....allowing for a warmer day overall for much of the
County warning forecast area on Tuesday. Highs on Tuesday will generally range from the upper 50s in
western WI to the upper 60s in western Minnesota.
Long term...(tuesday night through monday)
issued at 345 PM CDT Monday Mar 30 2015
The main focus of the long term will be the thunder threat for
Wednesday and the gusty winds developing again in the wake of the
cold front into Thursday.
The latest 15z sref probs of 30kts shear and 500 j/kg MUCAPE is
indicating small chance for severe weather threat lifting into
central Minnesota by late Wednesday afternoon. Deterministic models
slowed the front slightly...with the 12z European model (ecmwf) being the
slowest...with the front over western Minnesota by 00z Thursday. Will trend a
bit slower with the front and probability of precipitation...but not by too much just
yet....as the trough isnt even on the West Coast yet. Will trend
to likely probability of precipitation into southwest Minnesota by late afternoon...lifting north
along the front into central Minnesota. Strong low level jet to 50 kts
plus prognosticated into western Minnesota by 12z Wednesday...with hefty moisture
transport indicated. Precipitable water increase to around 1 inch by late
afternoon along the front...which should help support some
convective development. The middle level lapse rates are quite high
as well...which would indicate at least some small hail potential
on the onset of the convection along with a strong/gusty wind
threat. Expect this to develop shortly after 18z along the
front...and move east into the evening hours. It should trail off
in west central Wisconsin through 06z Thursday. At the moment...we have
30 to around .75 inch quantitative precipitation forecast forecast...with the higher amounts into
south central Minnesota.
Colder with strong cold air advection developing for Thursday. Should see
stronger winds developing Thursday afternoon across the west and
south...as the pressure rises works into the area. This should
linger into Friday as well. Still looks like the overall trend is
for slightly below normal into the end of the week...and back to
above normal into the weekend as the upper flow becomes more
west/southwest aloft...in the wake of the eastern Continental U.S. Trough and
the incoming western Continental U.S. Trough early next week.
Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 650 PM CDT Monday Mar 30 2015
Main concern this period is the chance of MVFR or low ceilings and
visibilities at krnh and Keau late tonight due to the light rain
that fell today followed by clearing and diminishing wind
overnight. Confidence is highest on the MVFR visibilities and that was
inserted into both tafs. Otherwise...VFR through the period. Winds
increasing out of the northwest on Tuesday with 12-15g20-25kts common at
the terminals for the late morning and afternoon.
Kmsp...no concerns this taf cycle with VFR conditions prevailing.
/Outlook for kmsp/
Wednesday...VFR. Rain showers likely/chance MVFR thunderstorms and rain in the aftn/eve. Winds S 20g35kts.
Thursday...VFR. Winds west 25g40 kts.
Friday...VFR. Winds northwest 10-15 kts.