Scientific Forecaster Discussion
fxus63 kmpx 131221 aaa
Area forecast discussion...updated
National Weather Service Twin Cities/Chanhassen Minnesota
621 am CST Fri Dec 13 2019
Short term...(today through saturday)
issued at 413 am CST Fri Dec 13 2019
A rather nebulous wave over the Dakotas is producing some areas of
light snow. There are two nearly stationary batches of low stratus-
one over western Minnesota/eastern Dakotas and the other over WI. In
between, mostly clear skies has resulted in some light fog and
temperatures in the single digits. Eventually clouds will fill in
as the system continues to progress eastward. Snow showers are
expected to become more numerous by late morning as the system
tracks across Minnesota. Kept the likely and categorical pops, mainly
due to the fact i'm fairly confident most locations will see snow
at some point today. However, it won't likely last long and the
likely or categorical pops are probably too long in duration at
any given point. Quantitative precipitation forecast has trended drier and now the forecast calls
for an inch or less across the entire forecast area.
Something to watch this afternoon and evening is the potential for
a bit of freezing drizzle. A mid level dry slot will follow
behind the snow showers this afternoon and ice aloft will be lost
across southern Minnesota, possibly into central Minnesota and western WI as
well. Any lingering precip would be liquid form. In most cases, a
loss of ice aloft means precip ends as opposed to transition to
freezing drizzle, but the abundance of low level moisture and
cyclonic flow with another vort Max moving through this evening
may be enough to get areas of freezing drizzle. Hrrr does show
this potential pretty well. Despite surface temperatures in the
teens, if freezing drizzle does materialize it should be of
minimal impact given its very light intensity.
Another shot of Arctic air will arrive for tonight and Saturday
with temps steady or falling through the day.
Long term...(saturday night through thursday)
issued at 413 am CST Fri Dec 13 2019
Arctic high pressure builds into the upper Midwest Saturday into
Sunday, leading to well-below normal temperatures and dry conditions
into early next week. Temperatures look to be coldest on Sunday when
the center of the high sits over the cwa, with lows dropping tens
below zero across western Minnesota and daytime highs likely
remaining in the single digits. Winds should remain fairly light
Sunday morning with the high overhead, but could see wind chills
reach advisory criteria across western Minnesota if winds maintain a
few mph Sunday morning. Temperatures moderate a few degrees for
Monday but then fall again Tuesday into Monday morning as a cold
front moves across the region. A system tracking along the Ohio
Valley will keep any appreciable moisture from reaching the area so
expect a dry frontal passage, other than a few possible flurries.
Northwest flow aloft develops by the middle of next week, with
guidance suggesting a clipper developing and tracking across
Ontario/northern Minnesota in the Wednesday-Thursday timeframe.
Models are't the best at resolving these weaker northwest flow
systems at this range, but a general consensus would seem to favor
the best forcing and bulk of precipitation occurring to the north and
northeast of the County Warning Area. Any snow would likely be light with little in
the way of moisture to work with. Towards the end of the week, the
forecast will depend on whether ridging develops across the
central US, and how far east it spreads into MN/WI.
Guidance differs on the eastern extent of the ridging and thus on a
possible warm up late next week. Temperatures could warm towards
normal values if ridging is stronger across the region, or remain
5-10 degrees below normal if it stays off to the west and northwest
flow persists aloft. Dry weather is expected overall.
Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 621 am CST Fri Dec 13 2019
Cigs are much better than expected early this morning with MVFR
cigs confined to just far western Minnesota at taf issuance time.
Eventually cigs will thicken and lower, which is likely to occur
mid to late morning depending on the location. Snow will develop
over western Minnesota mid morning and then track eastward in a narrow,
but potentially intense band. Following that round, there will be
a chance of snow and freezing drizzle across central/eastern Minnesota
and WI into the early evening.
Kmsp...MVFR vis is likely to persist for most of the morning, but
cigs will remain VFR until the afternoon. The best chance for snow
will be between 17-20z, with visibilities down to a mile possible.
IFR or low MVFR cigs will follow the round of snow.
/Outlook for kmsp/
Sat...MVFR/VFR. Wind northwest 10-15 kts.
Sun...VFR. Wind northwest 5 kts.
Mon...VFR. Wind west-northwest 5 kts.