Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
342 PM CST sun Nov 23 2014
Short term...(this evening through monday)
issued at 339 PM CST sun Nov 23 2014
The cold front is slowly making progress to the east this afternoon.
There is a Post frontal band of rain that is expected to continue
into the evening...but slowly lose intensity with time. The
800-600mb fgen then increases farther east across eastern Minnesota and
western WI between 04z-07z as the surface cyclone begins to deepen
and move northeast across the middle Mississippi River valley. Out
ahead of the cold front...we have struggled to shake an area of
dense fog in east central Minnesota and west central WI. This has held on
longer than expected and we should keep this in place until the Post
frontal air arrives everywhere across the County Warning Area between 03-06z. In the
short term...we have also joined National Weather Service offices to our south and west
and issues a Wind Advisory beginning tonight and lasting through the
days tomorrow. Wind the amount of precipitation has slowly trended down the
past couple days..the strong winds have remained a consistent
signal since the middle of last week. We are seeing 35-39kts from
the middle to the top of the mixed in west central Minnesota. This should
be good enough with the cold advection for gusts to 45 miles per hour...on the
low end of our Wind Advisory criteria. Fortunately...we now expect
little new snow and the snow pack has been settled by warmer temperatures
and light liquid precipitation.
Long term...(monday night through sunday)
issued at 339 PM CST sun Nov 23 2014
Biggest change expected in the long term is a pattern shift toward
the warmer end of things this weekend as we shed our northwest flow and
transition to a zonal flow and its associated milder Pacific airmass.
For the start of the long term...there is still a fair degree of
discrepancies between the models in how expansive wrap around precipitation
will be on the backside of a deep surface low that by Monday night will
be working into The Straits of Mackinac. NAM is the farthest east
with precipitation with very little if any snow falling across the mpx area
Monday night...with the Gem holding down The Fort on the west
side...with borderline warning snowfall for Eau Claire and
Ladysmith. For this forecast...followed the European model (ecmwf) idea...which was a
nice compromise between the east and west camps...with an
additional one to two inches overnight in our east...which would
bring storm totals between Monday/Monday night to between 2 and 3
inches out in Eau Claire/Ladysmith. At this point...we are not
anticipating snowfall amounts near 6 inches...so felt no headlines
Tuesday will will see high pressure quickly move across the
area...with the next clipper already arriving Tuesday night. 12z
models shifted south considerably with the 700 mb low with this
system...with the NAM/European model (ecmwf) taking it down the Minnesota river...with GFS
actually taking the 700 mb wave SW of Minnesota all together. Forcing/moisture
still look similar with this system to what models were showing last
night...with a quick 1-3 inches of snow falling just to the north of
the surface low track. Its just that axis has shifted from the northwest corner
of Minnesota to Hayward last night to more or less straight down I-94
today. Given the jumpiness still in the models...did hold probability of precipitation
around 50% until they settle in on a solution...but did shift
expected quantitative precipitation forecast/snow amounts SW from what the previous shift had.
After that...Thanksgiving day and Friday look cold...with highs
likely remaining below our average lows. Thanksgiving looks
dry...but as warm air begins to return...we may see a quick hit of
warm air advection snow Friday north of I-94 before that pivots north the rest of
For the weekend things are becoming considerably more muddled. The
23.12 European model (ecmwf) sped up considerably the transition to zonal flow...with
a rather crazy temperature gradient across the southern half of Minnesota on
Saturday...with 850 mb temperatures near -8c in central Minnesota and pushing +8c
down along the Iowa border. The GFS shows something similar...but on
Friday not Saturday. After that...this boundary looks to waffle
around the mpx region into next week...leading to lower than normal
confidence in the temperature forecast from Friday onwards.
For precipitation...the GFS/European model (ecmwf) show several rounds of precipitation
occurring north of this front as weak waves ripple across the zonal
flow. South of the boundary...precipitation looks minimal...but to north of
the boundary there could be several inches of snow from the weekend
into the beginning of next week. For now...this boundary looks to
settle in far enough north where this precipitation is prognosticated to mainly
fall along the international border.
Aviation...(for the 12z tafs through 12z Monday morning)
issued at 700 am CST sun Nov 23 2014
MVFR ceilings/visibilities will persist this morning as a warm front lifts
across the area. The worst conditions /and lowest ceilings and visibilities/
will occur north of the taf sites...but an improvement should be
seen this afternoon at the Minnesota sites. A cold front works across the
area this evening...with gusty northwest winds developing in its wake.
Areas of drizzle/rain over WI sites/primarily Keau/ will transition
to snow after sunset...with kmsp on the western edge of the snow/precip.
visibilities should remain around 5-6sm with areas of fog through the
morning. Tough call on the timing for VFR ceilings...if anything
expect the taf is too optimistic in going to VFR by 14z. Frontal passage
occurs this afternoon with winds shifting to the northwest around
21z...and gusts into the middle/upper 20s developing this evening and
persisting into Sunday...with sub-1800 feet ceilings returning.
/Outlook for kmsp/
Monday...MVFR/IFR ceilings chance -sn. Winds northwest 20g30 knots.
Tuesday...VFR. Winds west 5-10 knots.
Wednesday...MVFR/IFR chance -sn. Winds northwest 10kts.
Minnesota...Wind Advisory from midnight tonight to 6 PM CST Monday for
WI...dense fog advisory until midnight CST tonight for wiz014>016-023-