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fxus63 kmpx 121738 

Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1138 am CST Tue Nov 12 2019

issued at 1112 am CST Tue Nov 12 2019

Updated for the 18z aviation discussion below.


Short term...(today through wednesday)
issued at 408 am CST Tue Nov 12 2019

A sprawling 1040+ mb high sits over the middle of the Continental U.S. This
morning, leading to a frigid night for most of the country east
of The Rockies. Winds have been light overnight, but not calm,
which has prevented radiational cooling from reaching its full
potential. Expect lows to end up within a few degrees of zero,
with below zero readings most likely across central Minnesota
where winds are more calm, and southern Minnesota where some snow
remains on the ground. The rest of the day looks dry, with
southerly winds picking up on the back side of the departing high
and ahead of an approaching clipper. Temperatures look to warm
into the mid 20s across western Minnesota where warm advection
will be strongest, but remain in the teens across eastern
Minnesota ands west-central Wisconsin. Warm advection increases
into Wednesday as the clipper passes through the region, with
temperatures warming onto the mid 20s to low 30s by Wednesday

Cloud cover will be on the increase during the day as forcing
aloft increases ahead of an approaching clipper out of the
northern plains. The atmosphere is Bone dry ahead of this system
(0.07" of precipitable water on last night's sounding, a new record low for Nov
11) so it'll take time for any precipitation to develop despite
increasing ascent aloft and frontogenesis in the mid and low
levels. Expect light snow to hold off until early tomorrow morning
across west-central Minnesota, and spread east into west-central
Wisconsin through the morning. Light snow is expected to continue
into the afternoon, tapering off from west to east during the late
afternoon and evening. Precipitation amount look to remain light
given the dry airmass in place and typical low precipitable water amounts
associated with clippers, but pinning down accumulations and where
snow is most likely remains tricky, primarily due to differences
int he models with where the best frontogenesis sets up. Leaned
closest to the href, which shows probability-matched quantitative precipitation forecast amounts
of 0.1-0.2 inches primarily east of I-35, and generally less than
0.1 inch elsewhere. With snow ratios generally expected to be
around 12-14:1, this would place amounts around 2 inches for west-
central Wisconsin and around an inch or less elsewhere.

Long term...(wednesday night through monday)
issued at 408 am CST Tue Nov 12 2019

Progressive westerly flow through the long term forecast period will
bring multiple precipitation chances, but also help temperatures to
return back to near or slightly above normal values.

Wednesday night snow will taper off over west central Wisconsin.
In the wake of the clipper system, broad surface high pressure will
build in for several days, as mid-level ridging pushes into the
central Continental U.S.. this combination will bring several dry days, with
high temperatures moderating from the low/mid 30s on Thursday into
the 35-45 degree range for the weekend. By Saturday the
aforementioned ridge will have shifted to the eastern Continental U.S. And a
surface trough will have entered the Dakotas. Resultant southerly
flow over the area will help facilitate the warming, but also usher
moisture into the area ahead of the next trough. Both GFS and European model (ecmwf)
deterministic models indicate precipitation in the late Saturday-
Sunday time frame, although onset timing differs by about 6 hours.
Therefore probability of precipitation for the weekend will likely end up being higher than
the 30 percent currently included once temporal certainty improves.
At this point a mix of rain and snow looks to be the most likely
scenario for precipitation type.

The start of next week features northwest mid/upper flow. The GFS
has another wave passing over US, following on the heels of the
weekend system. However, the European model (ecmwf) is less amplified with the
shortwave and keeps it farther north with less impact on the area.
Therefore have only included 20 probability of precipitation at this point until agreement


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1112 am CST Tue Nov 12 2019

VFR conditions will continue through the night, before an
approaching weak system will bring light snow and MVFR cigs to the
area tomorrow. The forecast has trended more optimistic in terms
of the morning rush, with guidance suggesting it will take quite a
while to saturate the atmosphere. This makes sense given how dry
the atmosphere is currently. Southerly flow has developed across
the area and will continue through the night before shifting
northwesterly tomorrow.

Kmsp...main change was to delay onset of light snow. The morning
rush prior to 14-15z looks to see minimal impacts.

/Outlook for kmsp/
Thursday...VFR. Wind west-northwest 5-10 kts.
Friday...VFR. Wind NE 5-10 kts.
Sat...MVFR psbl. Wind S 10-20 kts.


Mpx watches/warnings/advisories...


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