Bill Schintler
EF4
A winter storm will bring several hours of moderate snowfall to central and northern MN on Tuesday. Snowfall will start late tonight and continue through late afternoon tomorrow. The following are forecasts for specific locations in Minnesota:
Twin Cities, MN:
Snowfall will start at 1:30 AM in the north metro and 2 AM in the south, while accumulating to 5.5 inches north and tapering to 4.4 inches across the south metro.
St. Cloud, MN:
Snow will start at 12:00 AM tomorrow with 5.9 inches accumulation.
Duluth, MN:
Snow will start at 5:30 AM tomorrow with 1.2 inches accumulation.
Discussion:
The WV loop indicates a departing SHRTWV over the upper-Great Lakes with an upstream wave and baroclinic leaf over MT. At 18Z, weak echos were starting to show up on the UDX, BIS, and GGW radar sites. The SHRTWV will take aim at the Upper-Midwest tonight. The SFC low will track SE from ERN MT into SD and then SWRN IA. The H85 low will track along the IA/MN border with a large temperature gradient over SRN MN during the first part of Tuesday. Looking at MDL performance, the GFS has been more consistent then the WRF over the last several runs. The SREF ensemble continues to favor a far more NLY track for the SFC/H85 lows and will be discounted. Recent trends indicate an earlier onset and faster progression of the system.
After 08Z, STG isentropic upglide develops along 284-294K SFCS; first over WCNTRL MN and then spreading EWD towards CNTRL WI through 18Z with upwards of 2g/kg mixing ratio FCST. A zone of impressive H7 frontogenesis shifts through CNTRL MN between 15Z and 21Z. Application of the Garcia method yields 4 to 5 inch SNWFL totals while assuming a precipitation duration of 8 hours. A snow/liquid ratio of 18:1 was assumed along I-94 with slightly higher ratios further N, which may be too conservative. The progressive nature of the system will help keep SNWFL totals at bay despite snowfall rates as high as 1.5 inches/hour along and N of I-94 between 18Z and 21Z. Following the passage of the system, a cold AMS will surge SWD with H85 temperatures of -12 to -14 C FCST. Looking ahead, a couple of SHRTWVs will ripple through otherwise zonal flow, with the next system affecting the area on Thursday. This weekend, the ULVL flow transitions to a split flow pattern with the SRN branch becoming highly amplified over the Four Corners area resulting in a period of interesting WX. One or more SFC systems should develop in response, bringing a mixture of winter WX to the upper-Mississippi valley and episodes of SVR WX to the SRN states.
- bill
1:30 PM CST, 12/29/08
Twin Cities, MN:
Snowfall will start at 1:30 AM in the north metro and 2 AM in the south, while accumulating to 5.5 inches north and tapering to 4.4 inches across the south metro.
St. Cloud, MN:
Snow will start at 12:00 AM tomorrow with 5.9 inches accumulation.
Duluth, MN:
Snow will start at 5:30 AM tomorrow with 1.2 inches accumulation.
Discussion:
The WV loop indicates a departing SHRTWV over the upper-Great Lakes with an upstream wave and baroclinic leaf over MT. At 18Z, weak echos were starting to show up on the UDX, BIS, and GGW radar sites. The SHRTWV will take aim at the Upper-Midwest tonight. The SFC low will track SE from ERN MT into SD and then SWRN IA. The H85 low will track along the IA/MN border with a large temperature gradient over SRN MN during the first part of Tuesday. Looking at MDL performance, the GFS has been more consistent then the WRF over the last several runs. The SREF ensemble continues to favor a far more NLY track for the SFC/H85 lows and will be discounted. Recent trends indicate an earlier onset and faster progression of the system.
After 08Z, STG isentropic upglide develops along 284-294K SFCS; first over WCNTRL MN and then spreading EWD towards CNTRL WI through 18Z with upwards of 2g/kg mixing ratio FCST. A zone of impressive H7 frontogenesis shifts through CNTRL MN between 15Z and 21Z. Application of the Garcia method yields 4 to 5 inch SNWFL totals while assuming a precipitation duration of 8 hours. A snow/liquid ratio of 18:1 was assumed along I-94 with slightly higher ratios further N, which may be too conservative. The progressive nature of the system will help keep SNWFL totals at bay despite snowfall rates as high as 1.5 inches/hour along and N of I-94 between 18Z and 21Z. Following the passage of the system, a cold AMS will surge SWD with H85 temperatures of -12 to -14 C FCST. Looking ahead, a couple of SHRTWVs will ripple through otherwise zonal flow, with the next system affecting the area on Thursday. This weekend, the ULVL flow transitions to a split flow pattern with the SRN branch becoming highly amplified over the Four Corners area resulting in a period of interesting WX. One or more SFC systems should develop in response, bringing a mixture of winter WX to the upper-Mississippi valley and episodes of SVR WX to the SRN states.
- bill
1:30 PM CST, 12/29/08
