Generally More Moderate Temps Arrive This Weekend; Fuzzy Details FollowOctober 9th, 2012 at 9:38 pm by Don Paul under 4 Warn Weather
As forecasted last week, a couple more shots of chilly air will reinforce the cool pattern in place since this past weekend. But a fairly abrupt turnaround will begin to take shape on Saturday, after a potentially widespread frost and freeze before dawn. During the weekend, an area of low pressure moving north of our region will provide a gusty warmup, accompanied by some showers–mainly on Sunday. After that, the details grow somewhat hazier.
It does appear unlikely that the lower 48 will be visited by any true arctic airmasses for some time, with a more zonal/west-to-east flow showing up in the mean. That’s the big, fuzzy picture. However, short wave low pressure systems are still likely to traverse this flow, producing ups and downs not yet discernible in this mean flow. Some ensembles and models have a trough trying to establish itself over the central U.S., while others keep that trough more to the west, which would allow a warm ridge to build up over the east. There is a great deal of “spread” between models and some ensembles, leading to a great deal of uncertainty in the details after Sunday. Confidence levels at CPC are only 2 out of 5 and 1 out of 5 respectively for the 6-10 & 8-14 day outlook periods. Although the “indices”, the AO, NAO, and PNA do not initially match up with the zonal flow all that well, other inputs keep models and ensembles in rough agreement that there will be no lasting western ridge/eastern trough pattern in that time period. That does not preclude a couple of those “ups and downs” amplifying within that moderate mean pattern, as I’d posted in the last thread.