11-7-12 Long term outlook
A cold front running from an extratropical cyclone center to another surface low in the south is expected to pass through our area early next week following the warm-up. The thermal gradient associated with this front is very strong and there is a significant potential for severe weather associated with the passage of the front in the area to our west. SPC even mentioned potential for severe weather in their day 4 outlook for Saturday. SPC predicted initial formation as supercells then likely merging into bow or a squall line.
The graphics I have included are from the GFS after initial formation, Sunday evening and Monday evening both at 0z. Primary concerns Sunday for affected areas would be straightline winds and heavy rain. The 500 mb trough has positive tilt at this time and the areas of strongest PVA seem to be just a little behind the precipitating area, so the precipitation is mostly right along the front. The graphics from the following day, Monday, show the 500 mb trough rotating more toward negative tilt. The area of PVA comes close enough to the front to cause there to be more stratiform precipitation behind the surface front than the previous day.
It is hard to say whether a changeover to snow will occur as this system passes. The air mass behind the front is very cold however the strong CAA works to shut down precip as temperatures decrease. SkewT analysis of GFS model soundings for KLAF shows conditions favorable for a changover to snow monday night into tuesday morning when precipitation ceases.
This long term outlook has been provided by Daniel Burgin.