1/14/15: Northwest Flow

I was out of the office yesterday so apologies for no update yesterday, but the overall trends discussed in the blog posted on Monday still seem valid.  In the short range (next 7 days) the upper level flow will generally be from the northwest.  The analyzed 200 mb (Jetstream) wind speed and directions from this morning shows the flow over the upper Midwest coming in from the prairie provinces of Canada.   This is a classic flow for Alberta Clippers to form as low pressure systems from the Pacific will redevelop on the lee-side of the Rocky Mountains in eastern Alberta and then that low will move very quickly along the jetstream into this region.

200 mb Wind Speed and Direction from 6:00 AM January 14, 2015
200 mb Wind Speed and Direction from 6:00 AM January 14, 2015

One such disturbance will move across especially northern North Dakota into northwestern Minnesota this afternoon into the early evening.  Snow amounts looks to be mainly a dusting (0.5″ or less).  Ahead of this disturbance the “clipper” will bring a brief surge of warmer air, but very quickly, behind the low the wind will transition back to the north or northwest drawing in cooler air once again.

Projected Radar Returns for Wednesday January 14, 2015
Projected Radar Returns for Wednesday January 14, 2015

A series of weak clipper, most of which only having  enough moisture to support minimal accumulations in narrow band is foreseen through early next week.  Today, Saturday (17th), Monday (19th) and Tuesday (20th) of next week.  Each disturbance will bring a brief warming following by cooler air.  Western North Dakota will catch the warmest of the days, with eastern North Dakota and western Minnesota recording highs in the 20s to the very low 30s on the warmest days, so clearly better than the past 3 weeks, but still not a lot of melting foreseen in those areas.

Progged Jetstream for Saturday, January 17, 2015
Progged Jetstream for Saturday, January 17, 2015

In the longer term, next week into the rest of January.  Abundant tropical moisture in the western tropical Pacific including a potential Typhoon will get drawn into the mean westerlies in eastern Asia.

ir2-l
Western Pacific Satellite

That “heat” will in turn build a ridge over Alaska which in turn will force the colder air over the Arctic to push down to the lower 48 states.

gefs_WP92_current
Track of potential Typhoon east of the Phillipines

 

The described process usually takes about 10 days to complete the cycle, meaning that in the next week, the clippers will bring variable weather, most days at least above average, but as we progress into next week and finish the month of January the temperatures are likely to once again drop to well below average.  How cold in turn it will get as has been the case with all the cold snaps since November will be determined by the snow pack available in any given geographical spot.  At the moment many locations do not have much if any snow cover outside of sheltered locations, but with several clippers moving across the flow and perhaps a snow event with this more significant shift later next week, perhaps there may be a bit more snow on the ground than is currently in place, yet at the moment no major snow events are foreseen, just lighter events.

Mean 500 mb (18,000 feet) flow and height anomalies on January 26, at 6:00 PM
Mean 500 mb (18,000 feet) flow and height anomalies on January 26, at 6:00 PM

After we finish the month of January on the cold side, at some point in early February we will likely jump into a warmer pattern, then finish February cold, meaning February appears to me to be finishing near average overall.

Daryl Ritchison