Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
347 PM CDT Monday Oct 20 2014
Short term...(this afternoon through tuesday)
issued at 1205 PM CDT Monday Oct 20 2014
Very quiet period in the forecast. Surface analysis shows an
elongated north-S oriented area of high pressure slowly moving in from the
west...expected to move atop the area overnight...then shift off to
the east during the day on Tuesday. Aloft...a ridge of high pressure over the
central Dakotas will move into far western Minnesota by daybreak Tuesday morning
then shift across Minnesota and WI during the day on Tuesday. This deep ridging
combination will keep skies nearly entirely clear for the period
through tmrw...aside from some wraparound moisture from a departing
upper level low pressure center over the eastern Great Lakes...bringing stratocu
down over mainly western WI. This cloud cover...along with any fair weather
cumulus clouds over Minnesota...will dissipate tonight through tmrw morning. Another
round of few-scattered fair weather cumulus may well develop Tuesday but will be of
little consequence. Ample sunshine has done little to overcome the
deep cold air advection ahead of the incoming ridge...keeping highs today in the
middle 50s to middle 60s. Clear skies with light winds will allow temperatures
to plummet to the 30-40 degree range overnight. While cold air advection will
continue tmrw for western WI...keeping highs in the low-middle
50s...modest warm air advection will occur for central-western Minnesota where highs tmrw
will range through the 60s...and possibly to near 70 along the South Dakota
Long term...(tuesday night through monday)
issued at 346 PM CDT Monday Oct 20 2014
The period will start off dry...but rain chances will increase from
west to east as an upper level system moves across the region during
the middle of the week. Once this system exits the region upper
level ridging will bring warm air and dry conditions through the end
of next week. The long range guidance shows the potential for a
return of 70 degrees for Friday and Sunday.
On Wednesday a shortwave will move across the region. Warm air
advection and isentropic lift ahead of this wave...together with the
upper level height falls will support precipitation chances in western Minnesota
on Wednesday...which will overspread the rest of the forecast area
Wednesday night before exiting to the east on Thursday. Rainfall
amounts will generally be around a tenth of an inch...with slightly
higher amounts along the I-90 corridor.
Looking ahead...dry and warm conditions will return with southwest
flow and h850 temperatures 11-14c expected Friday. There will be a brief
cool down on Saturday...but another surge of warm air returns
Sunday. Surface temperatures should easily exceed 70f if skies are
clear...but any clouds would limit the diurnal heating...so settled
on the higher end of guidance for temperatures...but did not go above that.
Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1205 PM CDT Monday Oct 20 2014
VFR throughout this taf set. Only concern for cloud cover looks to
be Keau as wraparound moisture from a departing upper level trough will
nudge midlvl stratocu southward over far eastern Minnesota into western WI. Keau may be
susceptible to some midlvl ceilings through late afternoon...otherwise
coverage will be no more than scattered for kstc-kmsp-krnh...with both
kaxn-krwf too far displaced from this cloud cover so will keep
them sky clear at initialization. Any cloud cover will dissipate this
evening into tonight as deep high pressure aloft moves into the area.
Winds will drop off at all sites to light/variable for much of the
overnight hours...then pick up from the east-southeast just before dawn.
Speeds then increases to 8-15 knots by late tmrw morning with some higher
gusts. No visibility restrictions nor precipitation expeceted this taf set.
Kmsp...VFR throughout with no visibility/ceiling/precip problems
expected. North-northwest winds through this afternoon drop off this evening to
lgt/vrbl...swinging around to the east. Winds continue to veer to southeast
tmrw morning and increases in speed after daybreak tmrw to 5-10 knots.
/Outlook for kmsp/
Wednesday...VFR. Winds south-southeast at 15g20kts.
Thursday...VFR with MVFR/rain showers possible. Winds south-southwest at 10g15kts.
Friday...VFR. Winds south-southwest 5kts.