Friday, December 23, 2016

Christmas storm update number one

/Issued 5:21 PM CST, Friday, December 23, 2016/

Source:  http://www.weather.gov/crh/

More information on the various headlines that are in effect for Sunday-Monday can be found by clicking on the links below.

Blue area on map:  Winter Storm Watch http://forecast.weather.gov/wwamap/wwatxtget.php?cwa=dlh&wwa=winter%20storm%20watch

Red area on map:  Blizzard Warning http://forecast.weather.gov/wwamap/wwatxtget.php?cwa=fgf&wwa=blizzard%20warning

For marine interests on Lake Superior - Gale Watch http://forecast.weather.gov/wwamap/wwatxtget.php?cwa=dlh&wwa=gale%20watch















-Storm timeline for Duluth and Superior

*Tonight - Drizzle near Lake Superior and light snow on top of the hill will end before 8 PM, the rest of the night should be dry but patchy fog could develop.  Low 25 to 30.  Total snowfall accumulation on top of the hill 1" or less.

*Saturday - Dry but generally overcast (Few peeks of sun possible) Winds from the north shifting to the east later in the day.  High 25 to 30.

*Saturday night - Patchy freezing drizzle and a few snow showers could develop especially later in the night.  East to northeast wind increases to 15 to 30 mph.  Lows in the 20s.

*Christmas day - *Winter Storm Watch for Duluth* Windy! East wind at 15 to 30 mph.  Patchy freezing drizzle and passing snow showers during the morning.  Occasional bands of heavier snow, sleet and possibly freezing rain developing after 1 PM.  High 25 to 30.

*Christmas night - *Winter Storm Watch for Duluth* Windy! East wind at 15 to 30 mph during the evening.  Occasional bands of heavy snow, sleet and freezing rain changing to rain especially closer to Lake Superior.  Precipitation diminishing after midnight.  Temperatures rising into the 30s.  Total event snowfall accumulation ranging from 1-4".  Some accumulation of sleet and freezing rain also expected.

*Monday - Turning colder with snow showers and flurries.  Temperatures starting out in the 30s, falling into the 20s, and possibly into the teens.  Gusty winds out of the west or southwest.

Source:  http://www.pivotalweather.com/

The two maps below show the major model differences between the NAM and GFS when it comes to the ice accumulation forecast for late this weekend.

-The NAM keeps the cold air in place during the majority of this storm which is why they are showing the significant ice accumulations.

-The GFS brings the warm air in much quicker, and it has support from the European model...In fact the EURO model shows temperatures rising to around 40 degrees in Duluth by late Sunday evening (Around midnight)

-With the low level jet as strong as it is in the model guidance for Sunday afternoon-evening, it would make sense that the warm air would surge up from the south causing a quicker changeover from ice to rain, similar to what the GFS and EURO models are showing.  But, the NAM has been locked in on a colder solution for a few days now, so for now just have to keep watching the model trends, and hopefully by this time Saturday will know a lot more.































Ice Accumulation Index and the impacts that can happen depending on wind speed and how much ice accumulation there is.  This table may come in handy on Sunday.

Note:  Right now based on today's model data the Ice Damage Index would fall in Levels 1-2 (Yellow & Orange)












Here's a table showing the different types of precipitation and how they form.


















The high off to our northeast will try its best to lock in enough cold air near the surface to keep a lot of the precipitation on Sunday in a frozen form; Meanwhile the strengthening low lifting northeast out of Colorado will pump warm air northward into the upper Midwest, much of this warming will occur aloft, and that is one of the reasons why there will be a risk for sleet and freezing rain until the surface temperature climbs a degree or two above freezing (32 F)
















Tonight's low temperature forecast.  Source:  http://graphical.weather.gov/




















Saturday's high temperature forecast.  Source:  http://graphical.weather.gov/




















Normal temperatures for Duluth on Saturday

High:  20
Low:     4

Sunrise Saturday:  7:52 AM CST
Sunset Saturday:   4:25 PM CST

Tim