Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1117 am CST Sat Nov 28 2015
Short term...(today and tonight)
issued at 440 am CST Sat Nov 28 2015
Early this morning...surface temperatures are the coldest of the
season so far across most of southern Minnesota and western WI...as the
surface high is parked over southern Minnesota...providing prime
radiational cooling conditions. Temperatures have dropped into the single
digits across a few different areas this morning.
The surface high will drift slowly east today...a simple forecast
with clear skies and light winds. As far as temperatures are
concerned...should warm up a few degrees over yesterday with the
winds becoming more southerly /albeit light/.
Tonight...temperatures will be slightly warmer as a deck of middle level
cloud cover moves in from the southwest ahead of the strong upper low
near the Rocky Mountain region. No precipitation is expected.
Long term...(sunday through friday)
issued at 440 am CST Sat Nov 28 2015
There is a significant snow event brewing for the Monday to
Tuesday time frame....with a swath of 6 to 12 inches likely in or
very near the forecast area. As it stands now...southwest
Minnesota is in the bulls eye for 6"+ snow using model consensus
What stands out with this event is the slow movement and almost
ideal storm track for heavy snow across the western half of the
forecast area. The moisture content is solid...but we would expect
that with this kind of low track and moisture advection on the
warm side of this system. Both the NAM/GFS wrap in precipitable waters between
0.50-0.60" across the forecast area by Monday morning. These
values would be right around the 90th percentile based on our mpx
The lift is really good with the 700mb low tracking across
central/northern Iowa and into southern WI...the 500mb 12hr height
falls near 200m just south of this middle level low track is also
very good. The top 15 cips analog matches to the 84hr GFS have
about 4-5 heavy snow events in the eastern Dakotas and western Minnesota
/27nov2001...26nov1993...27nov1994 to name a few/. All of these
produced 12"+ near the South Dakota/Minnesota border or across central Minnesota. So...the
question in the coming days wont be "will there be a winter storm
warning?"...it will be "where is the winter storm warning?" The
GFS is a little bit of a southeast outlier compared to the
European model (ecmwf)/Gem/ and even the extended NAM which is now getting into the
snow at the end of its run. The last two runs of the European model (ecmwf) 27.12z
and 28.00z have been very similar...while the GFS has shifted
first north and then back to the south over the past 5-6 runs. The
NAM hammers the area with snow and even brings the double digit
totals close to the west tc metropolitan. We'll see if the GFS can settle
out over the next couple days. The warm conveyor belt and dry slot
give question to the p-type in the eastern forecast area
/especially in west central Wisconsin./ We are are using fairly
modest snow ratios with an average of about 10:1 through the event
and still getting totals of 7 to 9 inches in western Minnesota. There is
potential to go as high as 13/14:1 for the ratio which would yield
Stay tuned to updates and the eventual winter weather headlines
coming out this weekend.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1120 am CST Sat Nov 28 2015
No aviation concerns over the next 24 hours with VFR conds and light
SW to S winds.
No aviation concerns with light SW wind...becoming southeast/east under 6
kts Sunday afternoon.
/Outlook for kmsp/
Monday...VFR becoming IFR or lower in snow/+sn late. Winds east-northeast 10 kts.
Tuesday...IFR in snow early. Poss VFR late. Winds NE becoming northwest 10-15 kts.
Wednesday...VFR. Winds northwest-west-northwest 5-10 kts.