Snow depth maps & an answer to TMIP.

A couple of points I wanted to hit: a look at snow depth across the region, an answer to TMIP's previous question, and how Winter Weather Warnings have changed this winter.

I pulled two maps of current snow depth off Wunderground.com, one of the Contiguous US (to the right) and one of the Midwest (below).

I like the bright spot around western Lake Superior, which is more apparent in the second map.

I think it's interesting to note that the yellow and orange color depths correspond pretty neatly with NWS Duluth's county warning area. I also think that some of the depths are a little high.

Information about the maps indicates that this information comes from the Air Force each day. The information also states that snow depth is usually under-estimated in the UP of Michigan. Mustn't there be a way to correct this problem?

TMIP's question: How radar works for mountains? Only sometimes there are cores on radar maps...

I posted a blog on how lake-effect snow (and other weather phenomenon) can slip 'under the radar' (linked here). TMIP was wondering how the mountains affect the radar beams and how there are permanent voids of missing radar data.

As an example, I took this screenshot (to the right) from KMQT (NWS Marquette) today. There are several examples of these cones of silence in this radar image.

As old as the hills.

Actually, the answer lies in the hills north of Marquette's airport. From Google Maps I took this topography image (to the left) of the area north of KMQT. I drew three lines in where the three largest voids occur on KMQT's radar images.



Elevation profile along the void.

On the left is the location of KMQT and the right is a point I picked in the middle of the void.

KMQT is located at 1444 feet amsl.

At 10 nautical miles (8.7 miles) the lowest radar beam is 510 feet above the elevation of the radar dome... 1444+510 = 1954 ft.

By connecting all the dots I got this image (to the right). By looking at this profile, it's easy to see why some areas are devoid of radar echoes.





Another look.

I found this graphic (to the right) from the AMS Online Journal - Volume 17, Issue 4, Augsut 2002 (linked here).

It shows the same idea - a hill or mountain blocking radar data.

This problem is encountered throughout much of the western U.S., with many mountain peaks and ranges above 5,000, not all the U.S. is covered by the same quality radar.


U.S. Radar Coverage Map.

There are several of these maps on the internet, I found this one (to the right) from the same AMS Online Journal as the previous graphic.

The darker shading, found mainly in the inter-mountain West, indicate no radar coverage below 10,000 feet above radar level. Closer to home, a close inspection of the map will reveal that northern Minnesota has an area that is not covered adequetly by base refectivity scans.

New Changes Occurred to Winter Weather Warnings and Advisories.

I'm not sure this story got any news coverage, though it was in the headlines of the NWS Offices this fall.

Certain types of Advisories and Warnings in the past have now been changed so that more winter weather will simply fall under one category -- Winter Weather Advisory or Winter Weather Warning.

Of course, some things haven't changed: Freezing Rain, Wind Chill, Blizzard, Ice Storm.

However, these will now be under one Warning: Sleet, Heavy Snow, Blowing Snow.

LES winding down, next storm winding up.

Today's Lake-Effect Snow (LES) event brought a couple impressive totals!

The table (to the right) shows the most recent NWS Spotter reports along the south shore of Lake Superior.

The event began around 7:00 this morning as a northeast wind brought a very large band of lake-effect snow to Douglas, Bayfield, and Ashland counties.

Now, at 17:45, winds are beginning to veer to the east and southeast, pushing the lake-effect snow band off shore of the Wisconsin counties.

Looking ahead to Saturday and Sunday.

Already a whole slew of headlines have been posted for all of North & South Dakota, as well as Minnesota & Wisconsin. This map (to the left) is cropped from MichiganWxSystem.com and shows all the counties under winter weather headlines.

A number of locations have been issued a Winter Storm Watch, so once more information can be determined, the Watches may be upgraded to Warnings.

It looks like most locations from the eastern Dakotas across northern Wisconsin will see up to 8 inches of snow by Sunday evening. In addition, the extremely strong winds will turn certain locations into a winter whirlwind... Blizzard Warnings have been issued for that threat. Wind gusts up to 40 mph will also create dangerous windchills across much of the region into Monday.

One picture sums it all up.

Again, I found a graphic that I like from NWS Milwaukee. I love how broad they paint the landscape sometimes :)

This image (to the right) is their Daily Weather Story and shows a pretty clear image of what to expect with the next storm system.

Lake-effect today, more snow tomorrow.

Heavy lake-effect snow band impacting the south shore of Lake Superior today.

Northeast winds and some low-level convergence due to the topography of western Lake Superior has produced a narrow lake-effect snow band over night. The band has been oscillating over the Minnesota counties along the north shore, but has begun shifting south this morning.

As of 7:00, the band began bringing heavy snow to Duluth and points east. This radar image (to the right) is from INFLOW-WI and shows radar echoes at 7:17 this morning.

Some possibly heavy totals today from the Lake.

This graphic (to the left) is from NWS Duluth and shows how much snow is expected from the lake-effect snow today. The heaviest areas are under a Lake-Effect Snow Warning, while the rest of the shoreline is under an Advisory.

It has been three days since our last snow, and we've used the time to plow & shovel our way back to normalcy. The last system was a little harsh with a foot of snow blown by the winds.

So far this winter...
Snow total: 27.1 inches
Max depth: 16 inches
Coldest temp: -18.4 degrees
Coldest windchill: -25.0 degrees

Next storm system is on its way.

Last weekend the northern part of Wisconsin and Minnesota were hammered by a snowstorm, yesterday and today it is the southern parts of Wisconsin that may see up to a foot of snow.

There is no break in the forecast of snow heading our way, and no end in sight to the bitter temperatures either.

This map (to the right) shows where the Hydrometeorological Prediction Center (HPC) has outlined the greatest chances that over 4 inches of snow will fall tomorrow and tomorrow night (Day 2).

Winter Storm Watches in effect.

Most of the region is under a Winter Storm Watch for the next storm, which is forecast to begin tomorrow (Saturday).

In addition to the possible 2 to 5 inches of snow from the lake-effect snow, up to 8 inches are possible from the snowstorm on Saturday and Sunday. NWS Duluth also highlights the possibility of lake-enhancement along the south shore. From their morning discussion:

WIDESPREAD SNOW TOTALS OF 8 INCHES OR MORE LOOK LIKELY
FOR NE MN AND NW WI. SYSTEM BEGINS TO WIND DOWN ON SUNDAY...
AS COLD ARCTIC AIR ONCE AGAIN MAKES A RETURN TO THE UPPER
MIDWEST. HIGHS WILL ONLY REACH THE SINGLE DIGITS...WITH
WIND CHILLS DROPPING WELL BELOW ZERO ONCE AGAIN ON GUSTY
NORTHWEST WINDS.

Topography around my location.

Bayfield Peninsula's elevation and the effect of topography on lake-effect snow of the South Shore.

A month or two ago I was toying with MapSource, the software for hand-held Garmin GPS units. I took four cross-sections of the Bayfield Peninsula, all the cross-sections run through my location on Maple Hill (the central dot in the cross-hairs of the map to the right).

I then took each cross-section and created four elevation profiles: south-north
west-east
southwest-northeast
northwest-southeast

Four elevation profiles surrounding the Bayfield Peninsula.

The first one is simply a cross-section showing the elevation profile of the Bayfield Peninsula. From the flat line of western Lake Superior in the west, across the sand hills in the middle of the Peninsula, to Chequamegon Bay in the east.

Each elevation profile contains a circled black square where Maple Hill is located on the Peninsula. All things considered, Maple Hill is only a bump on the eastern side of the Peninsula.

The second cross-section shows the elevation profile from the south to the north, with the Penokee Range of Wisconsin in the south, across the White River valley, through the Bayfield Peninsula, ending at Lake Superior in the north.

Compared to the Penokee Range, the Bayfield Peninsula is relatively small. However, this clearly shows how lake-effect snow runs into a "wall" and drops out on the snowbelts. The same ridge runs from the Keweenaw Peninsula of the UP down through northern Wisconsin, though the ridge has higher peaks in certain locations. Up to 1979 feet in Baraga County, MI (Michigan's highest point) and 1872 feet in eastern Ashland County, WI. In comparison, Lake Superior has a water elevation between 600 and 602 (depending on lake level) feet above mean sea level (amsl).

A list of high points for Michigan Counties can be found (here). Wisconsin counties (here).

The third cross-section shows the elevation profile from western Lake Superior to my northwest, through the Bayfield Peninsula, across the Bad River valley and up the Penokee Range in Iron County, WI.

Again, this is the 'wall' that the lake-effect snows run into when the wind blows off the lake.

And finally, the fourth cross-section shows the elevation profile from Wisconsin's Northern Highland Region to my southwest, across the Bayfield Peninsula, and the level of Lake Superior in the Apostle Islands to my northeast.

At first glance, I thought this profile was the least interesting, but I was wrong. The continuity (except the deeply incised river valleys) of the Bayfield Peninsula with the rest of the interior Highland shows that the Peninsula is simply an extension of the interior's topography.

Distance, heights, tilt of WSR-88D.

First off, I'm no pro concerning weather radar.

I've read some tutorials, I own and play with GRlevel3, and have tried to understand the extent and limitations of weather radar.

I've grabbed this chart (to the right) off the internet. Admittedly, I've no idea where I got it from... I simply found it in my files.

Each white diagonal line represents one tilt level of the radar beam as it sweeps around in a circle. Up to 14 tilts at various degrees make up one full set of radar images.

There are several different modes of operation for each radar.

This graphic (to the left) are cropped images from NWS's Jetstream Max, which show three of the main modes: Clear Air, Precipitation, and Severe.

Clear Air Mode uses 5 different angles and takes ten minutes to complete. To capture very small anomalies when precipitation is not present (e.g. wind shifts, smoke, bugs, lake-breezes), it is the slowest radar mode of operation.

Precipitation Mode scans 9 tilts in six minutes. When precipitation is detected by the radar, this mode is instantly turned on. It scans higher into the atmosphere than Clear Air Mode, so it better samples higher parts of thunderstorms and rain clouds.

Severe Weather Mode scans 14 slices in five minutes. It's very similar to Precipitation Mode, but the gaps are more completely filled in, so more of the atmosphere is scanned each time.

There are actually a couple other Modes being used, and I'm sure many more are coming in the next few years. The biggest challenge to overcome is how long it takes from one complete scan to another (a minimum of 5 minutes). When there are possible tornadoes five minutes can be too long. I have read that a Mode which can scan the same amount of sky in less time is rapidly being developed.

Onto what might interest someone in Oshkosh.

The lowest radar beam, in any of the various radar modes, is 0.5 degrees above horizontal. This means that as you increase your distance from a radar site, the radar beam is higher and higher above your head. On my awesome graphic (to the right) I've drawn in some black dots that show the base height over my guinea pigs... err, friends: Derek in Polk County, OSNW3 in Oshkosh, and my location on the Bayfield Peninsula. The five radar sites I reference are KARX - La Crosse, KDLH - Duluth, KGRB - Green Bay, KMKX - Milwaukee, and KMPX - Minneapolis.

Examples of distance versus height.

The right-most column is the height of the radar beam in feet above ground level (agl).

For example, above my head, the radar beam is approximately 4399 feet agl from KDLH. I used each radar site that scans the area above my three example locations.
Some implications...

Concerning lake-effect snow, which occurs under 4 or 5000 feet above the ground, the lowest radar beam will already be above that height more than 40 nautical miles from the radar site. The snowbelts of Wisconsin and UP of Michigan are beyond this threshold of KDLH and KMQT, so most lake-effect snow is miss simply by the location of each radar site.

Like lake-effect, any low level snowshowers will be falling at a level beneath any radar scan tilts.

I found a few reports online concerning the average heights above ground level where the maximum reflectivity (dBz) of hail are located (~9,500 ft agl), as well as the average height where mesoscale thunderstorm rotation occurs (~5,000 ft agl). Depending on how far from the radar site a severe weather event occurs, the radar beam may not be able to scan that feature.

Snow total map, bitter cold, more to come.

Over a foot of snow fell in Minnesota from the last storm, almost a foot in Wisconsin.

NWS Duluth put together this map (to the right) of all the reports they received from spotters, observers, and law enforcement officials. I won't post all the reports (there are quite a few), but here are the two highest from Wisconsin:

11.8" Washburn 5NW, Bayfield Co.
10.9" Washburn 4w, Bayfield Co.

Yeah,one of those is mine :)

And the highest from Minnesota:

15.5" Askov 4NNE, Pine Co.
15" Isabella, Lake Co.
15" McKinley, St. Louis Co.
14.5" Babbit, St. Louis Co.

The blowing and drifting snow forced highway closures.

During Sunday afternoon, Highway US 2 (this western portion runs 2120 miles from Everett, WA to St. Ignace, MI) was closed by law enforcement officials in two locations: just west of the City of Ashland and in the City of Superior. The rest of US 2 between Ashland and Superior was closed by 19:00 Sunday evening by State Troopers.

This map (to the left) shows road conditions at 19:00 on Sunday. The black and red color on US 2 in the northwest portion of the state is labeled as "IMPASSIBLE".

US 2 was reopened on Monday afternoon once road maintenance crews were able to clear drifted snow and ice from the roadway.

Wisconsin DOT updated their website yesterday with a new layout and new graphics, to bring Wisconsin up to par with neighborning states. A new interactive google map will provide the same color-coded road status information, in addition to other real-time hazards. The new page can be accessed (here).

Bitter cold temperatures and winds created dangerous windchills after the snowstorm.

Temperatures plummeted into the minus 20s and 30s overnight while winds stayed high enough to drop the windchill values even lower. The threat was great enough for the NWS offices to isssue Windchill Advisories and Warnings for a large portion of the Western Great Lakes last night.

This graphic (to the right) shows the NWS Duluth forecast area and the forecast windchill values across northern Wisconsin and northeastern Minnesota last night and into this morning.

My weather station briefly reported a windchill value of -25 degrees at 3:30 this morning, other places dropped much lower.

Here are several of the more impressive minimum windchill values in the region from last night from Minnesota and Wisconsin:

-52 Longville, Cass Co., MN
-46 Orr, St. Louis Co., MN
-45 Babbit, St. Louis Co., MN
-42 Inger 3SW, Itastca Co., MN
-42 Hill City, Aiktin Co., MN
-40 Grand Marais airport, Cook Co., MN
-37 Ashland, Bayfield Co., WI

More snow in the picture this week.

I've been reading of a possible upcoming low pressure system in area NWS discussions from the last two days, so I thought it was worth mentioning.

I'm glad I found this graphical Daily Weather Story (to the left) from the NWS Milwaukee, which highlights what they are monitoring between now and Friday.

It does seem like the models are still moving around a bit on the exact location of the low pressure, and therefore do not yet show a consistent location of heaviest snowfall. This system bears watching closely as we get closer to the event.

My final numbers from our first major winter storm this past weekend.

When I got up this morning to submit my weather report to the NWS, it looked like the cover of a Mannheim Steamroller CD album in my backyard. This picture (to the right) is what it looked like once the sky lightened up a bit.

11.8" of total snow.
1.48" of water equivalent.
15.9" the maximum snowpack depth.

27 mph maximum windgust.
-25 F lowest windchill reading.

-1.0 F afternoon high on Monday.
-18.4 F low temp Tuesday morning.

*** A low temp of 18.4 below zero already beats my minimum temperature measured last winter (-16.4 on January 19, 2008).

First Major Snowstorm of the Season!!

Major winter storm hitting the Northwoods:

Winter Storm Warnings and Blizzard Warnings have been in effect since yesterday across northern Wisconsin and northeast Minnesota. This graphic (to the right) shows the warnings and advisories from the National Weather Service offices. The storm is expected to peak Sunday afternoon and evening before tapering off to lake-effect snow on Monday.

Expected snowfall totals.

The heaviest axis of snow is forecast to fall in the Arrowhead of Minnesota, along the north shore of Lake Superior. This graphic (to the left) is from the NWS Duluth and depicts the expected snowfall totals from this storm system.

In addition, very strong northeast winds are beginning to funnel down Lake Superior. Duluth's harbor (KDYT obs) has already measured winds as high as 50 mph, which will bring blizzard conditions to the head of the Lake around Duluth and Superior, where US 2 has closed in the city of Superior.

Likewise, the strong northeast winds have been hitting the Chequamegon Bay area of northern Wisconsin (KASX obs) with gusts measured up to 40 mph. This has prompted the closure of Highway US 2 just west of Ashland, where the highway runs along Lake Superior. The combination of heavy snow and strong winds are producing a whiteout in the area of Fish Creek Slough near the intersection of Highway 13 and US 2.

A news article concerning the closures on US 2 can be found here on Duluth's Northland Newscenter (CBS/NBC) website (article link).

Wisconsin DOT road conditions can be found on this page (link).

Heavy snow across the northern third of the state.

This is a screenshot (to the right) of AccuWeather's radar at 12:16 this afternoon.

Snow began around 20:00 last night and has been accumulating since then.

A few reports via NWS Duluth and NWS Green Bay:

6.0" Brule 10S, Douglas Co.
6.0" Hayward 3W, Sawyer Co.
5.3" Washburn 4W, Bayfield Co.
5.0" Mason, Bayfield Co.
4.5" Manitowish Waters, Vilas Co.
4.5" Winchester 3NE, Vilas Co.
4.0" Grantsburg, Burnett Co.
4.0" Gile, Iron Co.
4.0" Glidden, Ashland Co.
3.0" Park Falls, Price Co.

Two pictures.

The first one is looking southeast across the front deck. The second is the backyard out the dining room window, looking west.

Currently, at 13:00 I have had a maximum wind gust of 27 mph from the ENE. Temperatures have dropped slightly from 30 degrees at midnight to 25 degrees now. Windchill values have begun to fall as the temps drop and the winds increase... the lowest windchill value so far has been 16 degrees at 10:00.