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In the 500mb maps for early April 2005 there was a high that formed on April 5 over the southwest. This high started over the eastern Pacific and slowly moved eastward for the next few days. It appeared on the charts the day that Jupiter went into a high- pressure aspect to both of the western eclipse points. The high manifested on the two 72° jet curves from the western points (blue curves). These jet curves were placed over the Great Basin. In figure 1 the high on the two 72° jet curves starts over the eastern Pacific and then slowly moves east. It was this high that served as a seed of the block that eventually brought up warm air into the Midwest region, in the middle of the month.
As the eclipse was happening on April 8th the southerly placed ridge pushed up into the Hudson Bay area. This was coincident with the descending path of a blizzard that dug south in the Basin and Range area. The eclipse had shifted the solar point from 26° Pisces to 23° Pisces sidereally placed. This put a high-pressure angular aspect from Jupiter on the solar eclipse point. The energies of the eclipse helped push a strong northward surging high-pressure value on the 72° jet curve from the new solar point (thick blue curve). This curve was the site of the strong northward surge. The southern flow to the west of the ridge produced a blizzard over Denver that brought up moisture from the Gulf of Mexico (red arrow). It is interesting to note that the blizzard only occurred on the eastern side of the mountains. Aspen, to the west of Denver hardly received any snow at all.
The ridge formation slowly drifted over the Midwest for the next week bringing up southerly flows and record warmth into the northern areas. This very narrow ridge seen in figure 3 became stationed over Hudson Bay. With the high over Hudson Bay the prevailing jet stream path was from the Texas Panhandle up into the Dakotas. The high was so narrow that an northerly flow from Canada did not bring down much cold because the warmth pouring up into the Midwest pushed the cold to the east of Chicago. This resulted in quite high temperatures for the spring in the Northern High Plains and Great Lakes areas. All of these features were linked to the shifting of the eclipse point on the 8th.
This blocking ridge pattern suddenly shifted into an unusual late cold wave for these same areas as the second eclipse of April 2005 approached. The set up for this movement began with a nodal shift on the 15th on the eastern pair of eclipse points. This movement dissolved the strong ridge but left a residue of high-pressure over the southern portions of the Midwest that still contributed to warmer than normal temperatures. However, with this motion of the node, the blocking pattern was dissolved. On the 21st, Jupiter moved in arc to low-pressure aspects to both of the western eclipse points (red curves). This left only the 72° jet curve from the eastern solar point carrying a high-pressure value for the entire grid. Two days later the node shifted to high-pressure values on the eastern solar point (heavy blue curve). This placed a strong, high latitude high over British Columbia. This motion pushed the jet stream up into the Gulf of Alaska shifting the continental pattern to cold in the northern High Plains and Great Lakes areas (arrow). Since the rest of the chart was dominated by low-pressure values an unsettled pattern evolved that brought snow to the Great lakes and Appalachians where only a few days before temperatures hovered in the 80's. Springtime patterns are often changeable and this is no exception. However, the rapid shift from record heat to record late snow is quite remarkable.