Tropical Moisture Will Bring Heavy to Excessive Rainfall with Possible Flooding This Week

Tropical moisture from the remnants of Odalys and Hurricane Polo will surge over the southwest into the central U.S. this week with several days of heavy to excessive rainfall which may bring limited to considerable flooding. Flood Watches have been issued through Wednesday in the southwest U.S. and moderate risk outlooks have been issued today through Thursday. Read More >

February 4, 2006
Winter Weather Event Review
Section 6: Summary

Back to the main event page for February 4, 2006

Section 1 -- Section 2 -- Section 3 -- Section 4 -- Section 5 -- Section 6

This was a very difficult warn verses no warn event. The forecasters were challenged with mixed signals leading up to the event. On the one hand the model trends showed an overall westward and warmer trend but also tended to linger precipitation longer when it was cold enough for snow. Also, HPC solutions trended back and forth and trended above warning criteria when Wilmington had to make the warn/no warn decision.

Some preliminary findings:

Although the model soundings and QPF showed the potential for warning criteria snowfall and lagged precipitation longer in the cold air the model signals (upper divergence, isentropic lift, favorable forcing) indicated that the accumulating snow would end quicker than the QPF indicated.
Conceptual models regarding path of the synoptic features and trends proved to be helpful in this case.
Boundary layer temperatures and precipitation type was crucial to the changeover and height of the freezing level was superior to thickness techniques.
The warm ground at the start of the event played a role in keeping snow accumulations down.
A surface low track along the spine of the Appalachian as initially indicated by the NAM solution is not a climatologically favored track.