Scientific Forecaster Discussion
fxus63 kmpx 180516
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1116 PM CST Fri Nov 17 2017
Short term...(this evening through saturday)
issued at 154 PM CST Fri Nov 17 2017
Early this afternoon, surface low was positioned across eastern
Nebraska with an inverted trough extending into Minnesota. East of
the trough axis which also corresponds to the 850mb trough,
southerly flow continues providing a continuous supply of saturated
air with dewpoints in the mid 30s. As expected for today,
temperatures warmed above freezing and no icing issues have been
reported. The moisture currently in place will not move much until
the arrival of the cold front coming down from North Dakota.
As of early this afternoon, the front just went through Alexandria
which noted a complete 180 degree wind direction change from 150
degrees (southeast) to 330 (northwest). The front will slowly move
through the region tonight, taking until tomorrow morning before
finally moving through the I-90 corridor. Expect drizzle and low
clouds to continue across the eastern third of Minnesota and all of
western WI. When the front eventually moves through, the low
stratus will depart but for Saturday we'll see a mix of sun and mid
and high clouds moving through.
Temperatures will be held in check with persistent northwest flow
tomorrow. Expect highs of 25 to 35 degrees across the region with
15-20 miles per hour northwest winds, gusting in the 20-30 miles per hour range.
Long term...(saturday night through friday)
issued at 154 PM CST Fri Nov 17 2017
The long term still consists of a roller coaster ride of
temperatures and little in the way of precipitation.
By tomorrow night, the next feature to watch will be the trough
off the coast of British Columbia because it will quickly lead to
surface cyclogenesis and a strong low pressure system emerging
from the Canadian rockies by early Monday morning. We'll begin to
see the start of the warm air advection Wing arrive as south-
southwesterly increase by Sunday afternoon. This will mostly
affect far western Minnesota as temepratures Sunday should be about 10
degrees warmer than Saturday.
As the 988mb surface low moves due east across far southern Canada
through Monday, continued warm air advection will persist through
the day. High temps across the area look to reach the upper 40s to
lower 50s. The cold front associated with the strong low in Canada
will move through overnight into Tuesday morning and it looks to
come through with no precip. It will bring much cooler air in
behind the front, so high temps will be about 20 degrees cooler on
Tuesday as opposed to Monday. Strong northwest winds will accompany
the arrival of the colder air.
At this point in the forecast, the guidance starts to disagree on
overall timing and evolution of the large trough over the Great
Lakes. The GFS offers a more amplified patter in which the trough
is deeper and remains in place longer, so it has gone colder for
Thanksgiving day. However, the European model (ecmwf) remains the more consistent
solution run to run. The European model (ecmwf) indicates a stronger upper level
ridge and pushes the trough northeast of the area, indicating warm
air moving in for Thanksgiving. The blended forecast indicates
highs near 40, but with more Reliance on the ECMWF, we think
chances are better that we will see warmer temperatures than that.
Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1115 PM CST Fri Nov 17 2017
Only minor changes needed for the tafs, with current timing for cigs
going back to MVFR late tonight/early Saturday morning looking good.
For today, expect northwest winds to gust into the mid 20 kts for Minnesota
terminals, while tonight, winds will back over to the west and
eventually SW, but will be under 10kts. High confidence in dry
conditions this period, with VFR conditions remaining in place once
reduced cigs move out this morning.
Kmsp...hrrr and NAM forecast sounding Show Low cigs may hang with US
through 14/15z, so a slight delay in improvements to VFR cigs may be
/Outlook for kmsp/
sun...VFR. Winds SW 5-10 kts.
Monday...VFR. Winds SW 5-10 kts.
Tuesday...chc MVFR. Winds northwest 15-20g30-35 kts.