Latest OUN AFD makes prediction for DRAMATIC return to winter, with all its associated nastiness, to ALL of the U.S. except western third.
Originally posted by WFO OUN
NEXT ISSUE IS THE MUCH-ADVERTIZED PATTERN CHANGE THAT EVENTUALLY
WILL BRING COLDER AIR INTO AT LEAST THE NORTHEASTERN HALF OF THE
CONUS. SLOWLY BUT SURELY...THE STAGE IS BEING SET FOR
AMPLIFICATION OF AN E-PACIFIC W-NOAM RIDGE AND A POSITIVE-PHASE
PNA PATTERN. FAIRLY PERSISTENT LOW-LEVEL WARM ADVECTION IS
PROGGED BY THE MODELS IN THE REGION OF EXPECTED RIDGE
DEVELOPMENT...DUE LARGELY TO THE RETURN OF NEGATIVE HEIGHT
ANOMALIES AND SFC CYCLONE DEVELOPMENT NEAR THE ALEUTIANS. THE
UPPER RIDGE DEVELOPMENT...WHICH SHOULD BE WELL UNDERWAY EARLY NEXT
WEEK...WILL DISPLACE THE COLD AIR NOW OVER ALASKA. THE HEMISPHERIC
THICKNESS MINIMUM...WHICH HAS MOVED TEMPORARILY E INTO THE BERING
STRAIT AND IS RESULTING IN TEMPS OF -40 TO -50 OVER NW ALASKA...
WILL BE NUDGED BACK W INTO SIBERIA. BUT THE COLD AIR FACTORY
EVENTUALLY WILL RETURN TO OPERATION DOWNSTREAM OF THE RIDGE
AXIS...OVER N AND CENTRAL CANADA...AS HEIGHT FALLS DOWNSTREAM FROM
THE W CANADA RIDGE SET UP A LOW NEAR HUDSON BAY. THIS AIR WILL
LIKELY OVERSPREAD THE NORTH CENTRAL AND NORTHEASTERN STATES BY
AROUND NEXT THURSDAY. DEVELOPMENT OF A HEALTHY ARCTIC SFC
HIGH...APPROACHING 1050 MB ON MOST MODELS...OVER NW CANADA INDICATES
THAT A SE-WARD MIGRATION OF THE COLD AIR E OF THE ROCKIES INTO
THE PLAINS WILL BE LIKELY LATE NEXT WEEK. BEST ESTIMATE OF INITIAL
ARRIVAL IN THE S PLAINS IS CURRENTLY NEXT FRIDAY...JUST BEYOND OUR
CURRENT DAY 7...WITH REINFORCEMENTS OF THE ARCTIC AIR AND A
POSSIBLE WINTER STORM SETUP BY THE WEEKEND OF 2/11-12 OR EARLY THE
FOLLOWING WEEK. MEANTIME...DRY/MILD CONDITIONS EXPECTED WED/THU
WITH DOWNSLOPE WARMING OF PREDOMINANTLY-PACIFIC AIRMASS.