Area Forecast Discussion
Issued by NWS Twin Cities, MN
FXUS63 KMPX 281210
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
610 AM CST Mon Nov 28 2016
.UPDATE...For 12z Aviation discussion below
.SHORT TERM...(Today and tonight)
Issued at 335 AM CST Mon Nov 28 2016
Early morning water vapor imagery and radar data illustrate the dry
slot centered over the forecast area, associated with the eastern
Dakotas upper low. A few spotty showers and light drizzle are being
reported, but there is a lull in the more widespread/organized
There will be two main areas of redevelopment today. The first will
be over west central MN related to the upper low, with the second
area of redevelopment anticipated along/east of Interstate 35 in
vicinity of the surface front during the late morning and afternoon
hours. While we did not see any nocturnal thunder activity locally,
the late morning and afternoon activity will have the potential for
some thunder with the surface low nearby. Non-supercell tornado
parameters (surface CAPE to 3 km and surface vorticity) peak along I-
35 (the front) this afternoon. Do not think we have enough
instability, otherwise it would be a potential tornado day.
High temperatures will be quite mild given the warm start to the
day, and expect lower 40s to lower 50s. These readings are 15-20
degrees above normal, but will likely fall short of record values
which are in the upper 50s.
Tonight precipitation will be primarily focused along the
western/northern fringes of the forecast area tied to the upper low,
and we should start to see some snow mixing in during the evening as
colder air works in.
.LONG TERM...(Tuesday through Sunday)
Issued at 340 AM CST Mon Nov 28 2016
The very highly amplified upper low will be slow to move out of
the Upper Midwest this week as a blocking type pattern develops
north across central Canada. Models have been forecasting this
scenario of the upper ridge across central Canada with a few minor
differences in the intensity and movement through Thursday.
Forecast confidence remains high as the mean upper low overhead
today will slowly fill and lift across the Great Lakes region by
the end of the week. The air mass will slowly cool overhead as
colder air rotates into the system, but nothing too extreme.
Therefore, the mixture of rain during the day and snow at night
seems likely. Any accumulations will be minor as the main lift and
deeper moisture will hold west of our region, but an inch or two
is possible in western Minnesota once colder air returns. Even if
precipitation develops or not, cloud cover will persist with
little diurnal change from nighttime lows, and daytime highs.
Next weekend remains questionable as the EC has a much different
forecast for a storm system moving out of the desert southwest,
vs. the GFS/GEM. Both the GFS/GEM continue with a more split flow
regime, with the EC more progressive, especially with the southern
jet stream. Due to these differences, forecast confidence is low
for next weekend.
Past next weekend, and how the aforementioned storm system affects
the central part of the country next weekend, a much colder flow
regime should develop the week of December 7th. This colder
outlook has been advertised enough by the longer range models to
have some support/higher confidence on a colder weather pattern
developing. Timing and how cold this air mass becomes remains the
big question. However, current models are forecasting -20 to -25C
850H temperatures behind this air mass flowing southward over the
Upper Midwest for the week of December 7th.
.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 610 AM CST Mon Nov 28 2016
Periodic showers will be possible through the period as an upper
level low rotates just west of the area, especially in west
central MN (KAXN). A wedge of drier air working northward from
south central Minnesota will bring scattering clouds to central MN
sites and improvement to VFR (primarily KRWF/KSTC/KMSP) this
morning. Other shower development (possibly even an isolated
thunderstorm) is possible later this morning and early afternoon
from east central MN into west central WI as a front lifts across
the area, but probabilities are low so only VCSH have been
included. Cigs will likely degrade back down to low-end MVFR again
tonight, with minor visibility reductions due to BR possible.
Southeast winds will gust from between 20 and 30 knots today.
VFR conditions look to be prevalent today now that the dry slot of
air is working in from the southwest. Could see some redevelopment
of showers later on this morning and afternoon in the vicinity of
a front, but coverage/probabilities are low.
/OUTLOOK FOR KMSP/
Tue...MVFR/IFR. Chc -RA. Wind SW 5-10 kts.
Wed...MVFR/IFR. Chc -RA/-SN. Wind NW 5-10 kts.
Thu...MVFR/IFR. Chc -RA/-SN. Wind NW 5-10 kts.