Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1143 am CST Friday Dec 6 2013
Short term...(today and tonight)
issued at 342 am CST Friday Dec 6 2013
A highly amplified upper level pattern was in place across North
America...with a Stout Ridge axis across central Alaska...and a deep
trough over the central United States. A powerful winter storm was
taking shape downstream of the trough axis across the southern
US...where widespread freezing rain is expected along the Arctic
front that marched through the upper Midwest a couple of days ago.
In the wake of this front lies the bitterly cold airmass that will
continue to bring temperatures on the order of 25 degrees below the
seasonal average for early December. Aside from the occasional
Diamond dust...dry weather will continue through tonight.
Long term...(saturday through thursday)
issued at 342 CST Friday Dec 6 2013
A high pressure ridge circa 1040 mb straddles the forecast area on
Saturday. After a night with lows in the 10 below to 20 below
range...readings will be pressed to moderate much above the zero
degree mark. Will see winds a tad lighter however...so wind chills
on Saturday night are looking to remain slightly warmer than advisory
criteria /25 below/. Confidence remains fairly high with respect
to the shortwave energy ejecting northeast from The Four Corners
region. Expect to see snow enter southwest/central Minnesota around 06z
Sunday as isentropic upglide on the 275k-285k surfaces ensues...and
then become widespread into east central Minnesota by Sunday afternoon.
This will be a fluffy snowfall...with snow ratios around 20-25
/enhanced by a deep dendritic growth layer/. Therefore think we
could see a solid swath of 1-3 inches from south/east central Minnesota
into west central...despite quantitative precipitation forecast values in the 0.10 to 0.15 inch
range. Sunday will also bring a brush with highs in the double
digits...with a reinforcing shot of colder air on Monday yielding
a return to single digit highs. Monday should be a dry day in the
wake of the trough...although a pair of fast clipper systems could
bring the opportunity for quick cosmetic snowfalls on Monday night
into Tuesday...and again Thursday night into Friday. Temperatures
will moderate into the upper teens to middle 20s on Thursday and
Friday...as western Continental U.S. Middle level ridging expands toward the
area...and 850mb temperatures attempt to surpass the zero degree mark.
Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1138 am CST Friday Dec 6 2013
High pressure will be sliding from the Dakotas toward southern Minnesota/northern
Iowa this period. Will result in another quite taf period with 8 to
12 knots west-northwest winds and mainly clear skies expected. High confidence
tafs all around.
Kmsp...no significant deviations expected from current taf.
/Outlook for kmsp/
sun...VFR with MVFR/IFR -sn likely by afternoon. Winds southeast at 5-10kts.
Monday...MVFR/-sn ending early...then VFR. Winds west-northwest at 15g25kts.
Tuesday...chance MVFR and -sn. Winds west 15g25kts.
Minnesota...Wind Chill Advisory from 9 PM this evening to 9 am CST Saturday
Wind Chill Advisory until noon CST Saturday for mnz041>043-
WI...Wind Chill Advisory from 9 PM this evening to 9 am CST Saturday