21. Pacific and modified polar air have jousted back and forth over the Plains this week. 22. The cold polar air mass met with humid subtropical air, leading to very low pressure. 23. But a new push of polar air into New England will retard the advancing sultry weather. 24. From September until February, frequent continental polar air masses coming from the East invade the area. 25. The boundary with polar air over Canada will be active from the Great Lakes to Montana. 26. Frequent surges of polar air have kept readings generally below seasonal levels for over two weeks. 27. A surge of polar air will reach from the Great Lakes to the lower Missouri Valley. 28. Behind this solar track, the sea and air grow warmer and the polar air currents retreat. 29. The boundary between polar air and Pacific air will be confined to the border ( sTetes. 30. The leading edge of a polar air mass will enter the Upper middle West on Wednesday.
