A major winter storm will affect the Upper Midwest on Sunday. The Twin Cities will be along the southern fringe of the snowfall, with heavier amounts remaining to the north. Gusty winds and much colder temperatures will arrive in the storms wake.
Twin Cities area:
Light rain or showers will start at 8 AM Sunday and change over to snow between 1 and 2 PM, north to south, across the metro. During the transition from rain to snow, a brief period of freezing rain will be possible. Accumulation will range from 1 inch along the south side of the metro, to 2 inches in the north, and 4.5 inches along a St. Cloud to Cambridge line before ending early Monday morning.
Duluth:
Light to moderate Snowfall will begin at 8 PM today. Snow will become heavy at times on Sunday, and accumulate to 11 inches.
Eastern Iowa:
Most locations can expect 0.25 inches of total rainfall between Saturday night and Sunday. A cold front will then sweep through late in the day Sunday, bringing falling temperatures and gusty northwest winds. Rain will change to light freezing rain between 5 and 6 PM. Freezing rain will then change to light snow by mid-evening. Iowa City will receive once inch of snow between 9 PM Sunday and 2 AM Monday. Locations north of I-80 will see a half-inch or less of snow accumulation.
Discussion - MN:
An interesting but challenging FCST is shaping up; as minor variations in the track of the SFC/H85/H7 lows have large implications regarding snowfall totals and type, and timing of precipitation type transitions. Models differ somewhat on the track; however, they have consistently agreed on the location of the H85 low on 00Z Monday. Both the GFS and WRF are trending towards an increasingly SLY H85/SFC track between 00Z and 12Z, 12/14; with the WRF exhibiting the most amplified track. During the morning Sunday, the consensus takes the SFC and H85 low further NW; this potentially keeps the Twin Cities region in the warm sector during much of the accumulation precipitation.
Today, WAA and isentropic lift will develop over NCNTRL MN, with light S developing in NW areas and ZR S of I-94. Meanwhile, a secondary area of lift will affect SERN MN through WCNTRL WI on Saturday with isentropic lift noted along the 290K SFC, however little more then some ZL or DZ should result as soundings are dry above 800mb. The main event starts to unfold tonight as large-scale assent overspreads MN beneath the left-exit region of a 120-130kt H25 streak. Associated with is a parade of H5 VOT ribbons embedded in the SWLY flow, which will translate across MN and WI between 12Z Sunday and 00Z Monday. Between 18Z and 00Z strong UVM in excess of -10ub/s develops along and N of the I-94 corridor in MN. Synoptic trends suggest an increasingly SLY trajectory of the 700mb low across ND/SD and E into CNTRL MN. This path shifts the deformation zone S along a line extending E and W through Little Falls between 18Z and 00Z Monday. Mixing ratios AOB 5 g/kg are indicated in this area. Additionally, the Duluth area will receive lake effect enhancement. A healthy fetch off Lake Superior will exist over the duration of the event through 18Z Sunday at which time winds take on an increasingly NLY component. I will go above guidance for snowfall totals in Duluth for this reason.
CAA along with a sharp SFC/H85 gradient arrives in MN on Sunday. The low will track over the Twin Cities late Sunday, while reaching Marquette at around 06Z Monday. Ahead of the low, deep tropical moisture from the Caribbean will surge N courtesy of a 60kt LLJ. Indeed; the GFS, WFR, and the SPC SREF ensemble indicate as much as an inch of total storm QPF in CNTRL/NCNTRL MN. Behind the low, an arctic AMS surges in with H85 temperatures pushing -30C! The result is an impressive baroclinic gradient over MN Sunday.
Discussion – IA:
Strong WAA is underway, with upstream Neodesha, KS; and Conway, MO profilers each indicating SWLY 70kt flow at 3kft. 10C H85 temperatures are currently noted over ERN KS. The CF sweeps through the eastern IA area late afternoon Sunday, with increasing post-frontal precipitation and a transition to S by 4Z as frontogenetical forcing increases in response to a secondary H5/H7 wave. The H85 front lags that at the SFC, and soundings will support ZR once SFC temperatures fall below 0C.
- bill
KD0DJG
11:30 PM CST, 12/13/08
Should be interesting to hear from my sister who lives in Fargo.
