NW Flow, Weatherman's Woe.


Saturday, January 22nd 2011, 8:39 am
By: News On 6


As Alan mentioned in his discussion, we are tracking a number of systems that will be moving across the state during the coming week. Any one of those systems will have the potential to wring out some precipitation, but since they are coming along at a fairly rapid clip, the available moisture will remain very limited. The flow pattern aloft is what we refer to as a NW flow, and it can lead to some real forecast headaches. Notice for example the chart on the right which shows the winds aloft at about 28,000 feet and the colors represent the strongest winds, i.e. the jet stream location.

The system that produced the snow on Thursday is one example and another similar system will be moving across the state on Sunday. However, the track of the Sunday system and the moisture supply is different enough that we are only expecting a slight chance of precipitation during the day. The problem is that some of the precipitation could be in the form of freezing drizzle first thing Sunday morning before switching over to a few snow flurries during the day. Any accumulation would be confined to the extreme NE counties or NW Ark, and not much more than a dusting there the way things stand at this time.

However, it will be turning colder once again after moderating into the 40s this afternoon we will struggle to get much above freezing during the day Sunday. Brisk northerly winds and the cloudy skies will help keep temperatures down, but since this is a rapidly moving but not particularly strong system, our winds should be back to the SW on Monday. That should result in temperatures moderating back into the 40s for Monday followed by several other weak systems during the rest of the week.

Each system will produce a shift in the winds, partly cloudy to at times mostly cloudy skies, and potentially a snow flurry or two somewhere along the way. But, at this time none appear to be strong enough to do any more than that. And, that is the difficulty in forecasting these NW flow events. There is always the potential that one of them will amplify much more strongly and much more quickly than expected, but picking out which one will do that is no easy task. Thus, the expression: NW flow, weatherman's woe.

At any rate, despite the rapid succession of systems moving across the state and barring any surprises, much of the coming week looks fairly quiet. In fact, we should be moderating rather nicely by Friday before the next shot of cold air arrives over the coming weekend.

As always, stay tuned and check back for updates.

Dick Faurot