Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kmpx 262040 
afdmpx

Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
240 PM CST sun Feb 26 2017

Short term...(this evening through monday)
issued at 220 PM CST sun Feb 26 2017

The short term period, tonight and Monday, looks to be fairly quiet
across the area. The frontal boundary currently bisecting the area
from southwest to northeast will continue to slide south/east and
essentially wash out overnight. This will take the few flurries
currently over the east out of our area by evening. We could see a
little light snow over the far northern portion of the forecast area
overnight as a weak shortwave moves by and helps moisten things
enough to take advantage of some weak isentropic ascent north of an
incipient surface trough/warm front. But, wouldn't expect much more
than a dusting from that activity overnight. Otherwise, we'll just
see an increase in mid/high clouds overnight, which may thin some on
Monday, although the northern part of the area will likely hold onto
a thicker deck for most of the day.

Long term...(monday night through sunday)
issued at 240 PM CST sun Feb 26 2017

The main forecast concerns are precipitation type and quantitative precipitation forecast amounts
late Monday night, and into Tuesday which will have some impact
on travel if freezing precipitation develops.

The ec & GFS differ on how the northern short wave and southern
short wave interact late Monday night and into Tuesday which leads
to surface low placement and overall quantitative precipitation forecast amounts. The Gem is
closer to the GFS but has more energy on the initial warm air
advection regime which producing more quantitative precipitation forecast in southeast Minnesota,
and into portions of west central Wisconsin late Monday night.

The comparison between the ec & GFS is related to the phasing of
the two waves. The GFS has more influence on the northern wave
which keeps the bulk of the precipitation north/northeast of mpx
forecast area. The ec keeps the northern short wave further to
the west and allows more energy northward with the southern short
wave. This will allow for a broader area of precipitation to form
across southern Minnesota, vs the GFS Tuesday. The 12z run of the
gefs also supports the deterministic GFS which keeps the bulk of
the precipitation across central and northeast Minnesota.

Neither the GFS/ec doesn't support a lot of quantitative precipitation forecast Monday
night/Tuesday morning when temperatures are close to the freezing
mark. Thus, if precipitation develops, it should be more drizzle
than steady rainfall as temperatures aloft will be warm enough.
Therefore, leading to a higher probability of icing. The forecast
will continue to support a mixture of freezing precipitation/snow
in areas where the depth of the moisture is greatest in central
Minnesota. Otherwise, no major impacts are expected.

Another element which is related to the northern wave influence of
the GFS is the faster ending of the precipitation Tuesday
afternoon before colder air arrives, changing the precipitation over
to snow. However, the ec, which holds both waves further to the
west/southwest, holds onto the precipitation longer and
eventually changes the precipitation over to snow late Tuesday,
into Wednesday morning. This could lead to light snowfall amounts
as far south as the Twin Cities by Wednesday morning.

Otherwise, the main extended period will transition to a cool
period for Wednesday, Thursday and Friday before more zonal flow
develops and temperatures begin to modify next weekend. 40s/50s
are still likely for next Saturday, and possibly into Sunday.

&&

Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1115 am CST sun Feb 26 2017

The only issue this forecast period will be some MVFR for the
first few hours, mainly over the North/East portion of the area,
in association with the frontal boundary moving through. After the
front passes, we should see VFR conditions, although there will be
an increase in mid/high clouds tonight into Monday. The weak
surface ridge building in behind the front will quickly shift east
overnight, with southerly flow developing by morning.

Kmsp...only item of concern/uncertainty will be the extent and
duration of some MVFR ceilings at the start of the period.
However, don't expect them to stick around too long and will only
carry a mention for an hour or two.

/Outlook for kmsp/
Monday night...MVFR expected overnight, IFR possible. Chance of
light rain. Southeast wind 5 to 15 kt.
Tuesday...MVFR expected, IFR possible. Chance of light rain/snow.
Southeast wind 5 to 15 kt becoming west.
Tuesday night and Wednesday...MVFR possible. Chance of light snow.
Northwest wind 10 to 20 kt.
Wednesday night...MVFR possible. Chance of light snow. Northwest
wind 5 to 15 kt becoming northeast less than 10 kt.
Thursday...VFR. North wind 5 to 15 kt.

&&

Mpx watches/warnings/advisories...
WI...none.
Minnesota...none.
&&

National Weather Service Glossary of Abbreviations