/Issued 8:34 PM CST, Wednesday, February 19, 2014/
250mb PV map valid for Thursday Evening per 00z NAM. Note how the black lines tilt in a more SE-NW direction in Minnesota and Western Wisconsin. This is a sign that the upper trough is becoming negatively tilted which is indicative of a very powerful storm.
SREF map valid at 6 PM Tonight – basically a U-shape trough configuration over the Northern Rockies This Evening. Now watch how the trough changes as we move to Thursday Evening.
Here is that map for Tomorrow Evening. Again a negative tilted trough develops. Very powerful storm.
00z model data is coming in and 1st out of the gates is the NAM.
-NAM has trended west compared to it’s previous 2 runs. Low pressure tracks into Southern Wisconsin then into Northeast Wisconsin Tomorrow Night. Earlier runs had the low more to the east, basically lifting through Western lower Michigan.
-15z SREF model is next up, this model has also beefed up snow totals across the Northland. I love the plume page from the SREF. The latest run shows a minimum snow amount of 4″ in Duluth and a maximum amount of 18″. The mean between all the models has gone up to 10″. Earlier runs had a mean closer to 5″.
Here’s a link to the SREF plume: http://www.spc.noaa.gov/exper/sref/fplumes/index2.php?YMD=20140219&RT=21&PRM=Total-SNO&SID=DLH&INC=ALL&NNC=&max=&min=&mZOOM=4&mLAT=37.77478874678&mLON=-96.042896875&mTYP=roadmap
-So the main theme This Evening at least in the SREF and NAM is for increased snow totals in the Twin Ports. New GFS run rolls out in a bit.
As for timing:
Most of Thursday may be okay here in Duluth and Superior, still cannot rule out some patchy light snow or light freezing drizzle from time to time, but the more widespread snow (possibly heavy) looks like it will arrive after 3-4 PM.
Thursday Night looks pretty ugly with snow and increasing winds which will cause considerable blowing and drifting snow.
The surface low is forecast to deepen considerably from Thursday to Friday AM. 992-994mb Thursday AM to around 972-975mb by early Friday AM.
Stay tuned for more updates.
Tim
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