Scientific Forecaster Discussion
fxus63 kmpx 200624
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1224 am CST Wed Nov 20 2019
Short term...(this evening through Wednesday afternoon)
issued at 245 PM CST Tue Nov 19 2019
Widespread stratus has remained in place this afternoon thanks to a
stagnant weather pattern and plenty of moisture in the boundary
layer. Expect cloudy skies to continue into tomorrow as as
increasing southeasterly winds advect in even more moisture and
provide plenty of isentropic ascent to reinforce existing cloud
cover. Expect areas of mist and fog to develop overnight as the
boundary layer continues to moisten and temperatures cool, with the
densest fog expected over west-central Wisconsin. Visibilities less
than a mile look possible across these areas, with patchy dense fog
less than 1/4 mile also possible near river valleys and other low-
lying areas. May need a dense fog advisory overnight for a few
western Wisconsin counties if these low visibilities become more
widespread, but held off on any headlines for now. Lows tonight are
expected to hover around freezing across central Minnesota and west-
central Wisconsin, so can't rule out some patchy freezing fog/mist
and a few slick spots across these areas tonight.
Temperatures will warm into the upper 30s across central Minnesota
to near 50 across southern Minnesota as southerly warm advection
continues ahead of the an approaching area of low pressure.
Increasing isentropic ascent will continue to moisten up the
atmosphere, with areas of drizzle or even light rain possible by
early to mid afternoon. More widespread rainfall is expected to hold
off until Wednesday evening when the low and better forcing aloft
Long term...(wednesday evening through tuesday)
issued at 245 PM CST Tue Nov 19 2019
No significant changes from the previous forecast. Confidence
remains high in widespread precipitation developing Wednesday
afternoon, and then departing the region on Thursday. This system
will be on the warmer side, so it looks like most locations will see
rainy main. There will be a change over to snow, but this occurs as
the storm is exiting the region. Friday will be dry and cooler, but
temperatures warm into the weekend. Looking ahead, the mild and dry
weather will continue into the first half of next week, but there is
a chance that a large storm system could bring rain or snow to parts
of the region. Uncertainty is very high with the system later next
Models are in good agreement with the Wednesday/Thursday system.
Cyclogenesis will commence over the High Plains of Colorado and
Kansas Wednesday morning, and the system will lift northeast towards
the Great Lakes on Thursday. As it does so, warm air advection will
lead to rising air and saturation across the upper Midwest, with
most if not all locations seeing precipitation Wednesday night.
Thermal profiles are warm enough for rain at most locations, but
parts of west central and north central Minnesota will have a change
over to snow overnight into Thursday morning. This change over will
migrate eastward as cold air wraps in behind this system, but a
longwave trough upstream over central Canada will push southeast and
drive our storm system out of the region by Thursday afternoon.
Surface high pressure will follow for Friday, and westerly flow
aloft will bring warmer air across the region for Saturday and
As for the potential storm late next week - several things have to
come together just right for a storm to bring snow to your location.
This system is a combination of a cut off low off the coast of
California, together with a jet streak that can be traced back to
central Asia. If we are able to phase these two systems and develop
a cyclone, it could still end up being warm enough for mainly an all-
rain event. In other words, keep checking back on the forecast over
the weekend and into early next week, but don't get too concerned
about any one particular solution. The track and rain/snow line will
vary considerably over the next few days.
Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1224 am CST Wed Nov 20 2019
IFR conditions continue across WI, with MVFR cigs over Minnesota.
Clearing is advancing northeast across southwest Minnesota, which should
bring VFR conditions to most of the taf sites by late this
morning. Rain will develop this evening with conditions
deteriorating quickly to IFR.
Kmsp...cigs should remain just above 1.7 kft overnight, with
several surrounding obs at or above 2 kft. Clearing of low clouds should
take place around 15z.
/Outlook for kmsp/
Thu...MVFR/IFR likely. -Ra transitioning to -sn through the am.
Wind northwest 10-20 kts.
Fri...VFR. Wind west 5 kts.
Sat...VFR. Wind west 5-10 kts.
WI...dense fog advisory until 9 am CST Wednesday for wiz014>016-