Followed by lower than normal temps the following week.
By: Steve Gregory , 10:13 PM GMT on January 17, 2017
The pattern change continues to be on track, with colder than normal Temps expected to develop across the southern US during Week 2 - following the warmest ‘same week’ (Week 1) Temps in decades. Amazingly above normal Temps are overspreading much of the nation but will trend back down towards more normal levels in the northern US by the end of JAN and on into the opening days of FEB.
The breakdown of the near perpetual upper level ‘block’ in the north-central NORPAC but continuation of the highly progressive flow pattern – and resulting zonal-like flow pattern across much of NORAMER – has eroded away the deep, arctic air mass over much of Canada while also bringing above to much above normal Temps from the Rockies eastward. In some locations, daily average Temps during Week 1 will run well over 30 degrees above seasonal norms, with potential record breaking values.
By later this week, a developing long wave TROF from Alaska to just off the west coast will deepen further as it shifts towards the E/SE as individual short wave TROFs first move southeastward on the west side of the long wave TROF axis into the SW US before turning eastward - eventually moving across the Gulf states region. The below normal upper level heights combined with widespread & prolonged periods of Precip will cause surface Temps to fall below normal across the southern half of the nation starting next week.
At the same time, upper level heights will be rising across Canada, with much above normal Temps developing during the week ahead and continuing thru Week 2 (and possibly longer, especially over eastern Canada). And while heights will gradually fall off in the northern US and Canada during Week 2 - along with a more northerly flow developing over Canada - the absence of true arctic air over southern Canada means Temps will only manage to gradually fall to near normal levels over the northern US during by the end of Week 2.