Saturday, March 19, 2011

3/19/11: Saturday's Weather Report

Issued at 4:15 PM CDT, Saturday, March 19th, 2011

Weather Headlines:

-Tonight's Full Moon (The Super Moon) is the biggest in 18 years.
-Rain or mixed precipitation develops Tonight.
-Sunday/Sunday Night will be wet at times.
-Strong winds expected in the Twin Ports Tuesday-Wednesday.
-Winter storm potential Tuesday-Wednesday?
-Official start to Spring will occur at 6:21 PM CDT Sunday.

Forecast Discussion for Northeast Minnesota and Northwest Wisconsin

Today's Weather:

High pressure of 1034mb was centered over the Eastern Great Lakes late Today with low pressure of 1002mb covering the Northern Rockies.  Partly-mostly cloudy skies were found in our area Today with a few light rain showers or sprinkles affecting areas W-NW of a line from Crane Lake to Brainerd, but with dry air in place (dewpoints in the 20s) much of this precipitation which has been detected on radar was not reaching the ground.  Highs Today were in the 40s, but 30s were common along the North Shore of Lake Superior down through the Twin Ports.  Winds Today were out of the south or east at 10-20 mph.

Today's Upper Level Analysis:

Southwest 500mb flow was developing over the Upper Midwest as a potent upper level trough covers the Western U.S. while another upper level trough heads east through Quebec Province and the Northeast U.S.  One system embedded within the Western U.S. H5 trough was pushing E-NE through the Central Rockies Today per water vapor satellite imagery with the next system spinning offshore of Washington and Oregon, with a seperate upper low located west of California.

Tonight:

Southerly low level jet increasing to 35-45 knots will transport deeper moisture north into our area Tonight as low pressure moves into the Northern Plains.  Showers will become more widespread in Northern Minnesota and Northwest Wisconsin Tonight as skies become mostly cloudy.  With 850mb temperatures holding around zero degrees C, some of the showers could mix with or change over completely to wet snow or sleet.  The best chance for this frozen precipitation would be in Northeastern Minnesota especially in higher terrain areas.  Lows Tonight will be in the 30s with south or east winds at 10-20 mph.

Sunday and Sunday Night:

Low pressure will pass by to our west-north during this period with a secondary low tracking northeast from Iowa.  Both lows will merge to one low pressure center by late Sunday Night.  Areas of rain showers will continue on Sunday with some wet snow or sleet possible as well, mainly in Northeast Minnesota in higher terrain areas.  The bulk of the rain/showers for Sunday Night should be confined to Northwestern Wisconsin with lesser chances for rain in Northern-Eastern Minnesota.  The rain in Northwest Wisconsin should end from west to east during the night.  Mostly cloudy skies are expected during this period with highs Tomorrow in the 30s and 40s with lows Tomorrow Night in the 20s in Northern Minnesota with 30s elsewhere.  Winds on Sunday will be out of the south or east at 10-20 mph with winds turning to the west, southwest, or northwest at 10-25 mph Sunday Night.

Note:  Precipitation totals from Tonight through Sunday Night should generally be in the 0.10"-0.25" range across our local area with some localized higher amounts possible in Northwest Wisconsin.  Snowfall totals of 1-2" are possible in Northeastern Minnesota (generally in higher terrain areas)

Extended Forecast:

Monday and Monday Night look dry at this time as one system exits to our east while a second one heads through the Rockies.  Highs on Monday will be in the 30s and 40s with lows Monday Night in the 20s with some teens in Northern Minnesota.

Tuesday and Wednesday, March 22nd-23rd continues to be a period to keep a close eye on as there is a threat for a winter storm for portions of the Northern Plains and Upper Midwest.  Low pressure in the 995-1000mb range is forecast to move from the Western High Plains, through Iowa, to south of Chicago Illinois during the Tuesday-Wednesday time period.  At the sametime this is happening, there will be a massive 1040mb high pressure system setting up shop over Hudson Bay/Northern Ontario Province (a common occurrence this time of year)  The majority of the forecast models are in agreement on this track mentioned above, but the NAM (12z run) is farther south.

The northern extent of the precipitation shield seems to be in more disagreement with the computer models versus the track of the low.  The GFS and last few runs of the SREF models are the farthest north with the heavier precipitation.  The 12z GEM-GLOBAL has trended north, although it shows a much sharper cut-off to the precip compared to the GFS and this seems a bit more realistic when you have such a strong high off to the north which will advect dry air south into our area.

This storm will be very complex and also a slow mover as the overall 500mb pattern becomes more amplified after Monday of next week.

There likely will be some fluctutations north and south with the precipitation shield in coming days, but as it stands now it appears that the heaviest band of precipitation will fall from from the Dakotas through Western, Central, Eastern, and Southern Minnesota with Northern Minnesota on the edge.  As for precipitation types, it still looks like the bulk of it will fall as snow for our local area, but there is a threat for some freezing rain or sleet Tuesday Afternoon/Evening especially south of a Backus to Twin Ports to Mercer line.

The worst conditions based on latest model projections would be from Tuesday Night through about midday Wednesday.

East to northeast winds will also increase Tuesday and Wednesday due to the pressure difference between the high and low.  It's likely that wind gusts will exceed 30 mph in the Twin Ports area, and gusts well over 40 mph are certainly possible.

The potential does exist for a 6" or greater snowfall from late Tuesday through Wednesday, especially south of a Bemidji to Grand Rapids to Two Harbors line.

5 Day Forecast for Duluth/Superior

.Tonight...  Becoming mostly cloudy.  Occasional rain showers developing after Midnight.  Some wet snow or sleet could mix in with the rain at times.  Low 30 to 35.  Wind east to southeast at 10 to 20 mph.

.Sunday...  Mostly cloudy.  Occasional rain showers.  Patchy fog also possible.  High 37 to 40.  Wind southeast at 10 to 20 mph.

.Sunday Night...  Considerable cloudiness.  Rain showers possible, mainly early.  Low 31 to 35.  Wind becoming west at 15 to 20 mph.

.Monday...  Partly sunny.  High 40 to 45.

.Monday Night...  Partly cloudy.  Low 20 to 25.

.Tuesday...  Becoming mostly cloudy and turning windy.  Snow or mixed precipitation possible late.  High 30 to 35.  East to northeast winds could occasionally gust over 30 mph.

.Tuesday Night...  Windy with snow possible.  Mixed precipitation possible during the Evening.  Low 20 to 25.  East to northeast winds could occasionally gust over 30 mph.

.Wednesday...  Breezy with snow possible.  High 25 to 30.  East to northeast winds could occasionally gust to 30 mph.

Normal temperatures for Today

High:  35
Low:  18

Sunrise Tomorrow:  7:12 AM CDT
Sunset Tomorrow:   7:21 PM CDT

Tim