April Forecast Follow-Up
After a warm-up along the East Coast and late-season snows across the Upper Midwest in mid-April, the weather pattern stays active heading into the second half of the month.
The April forecast outlook from March 15th predicated above average temperatures from the southern Rockies/Plains into the Southeast, with below average temperatures across the Great lakes and interior New York/New England. So far, temperatures have been above average into Ohio, Pennsylvania and southern New England, but that is expected to change.
A strong cold front will push well below average temperatures into the East Coast for the period between April 16th and 19th. The greatest departures from average should be experienced from April 16th into the morning of the 17th. Temperatures in many areas will verify between 10 and 15 degrees below average, with some greater depatures possible. This means frost and freeze conditions for many areas on the morning of the 16th and 17th. A trough responsible for the cooler air will gradually relax and shift east, allowing for a moderation in temperatures for the 18th and 19th. This cooler air will work to offset the month-to-date temperature departures closer to average and below average in some cases.
With the eastern U.S. trough lifting away, some ridging will build across the Plains. An already dry season should see a continuation of below average precipitation. The period from April 20th to 23rd should feature the warmest temperatures compared to average coupled with the highest threat of fire-weather concerns. As the soil becomes drier, this will allow for greater diurnal temperature variences and hotter daytime high temperatures.
A change in the overall pattern should allow for a trough to dig into the West Coast by April 22nd and 23rd. As the trough propigates eastward, there is the potential for a severe weather sequence or series of thunderstorm events between April 23rd to 25th from the eastern slopes of the Rockies into the Plains and Midwest. It is unclear at this point how significant this event could be and just how far north (or south) the trough sets up. Stay tuned for more information on this potential event in the coming days as new model guidance comes in.
Depending on the progress of the aforementioned trough, there could be another period of below average temperatures across portions of the East. At this point, the Great Lakes and Northeast would be among the most likely areas to be impacted. This trough will likely not be as amplified in the East as the current April 15th one is.
Overall for the period, temperatures should verify near or above average for much of the country. The exception would be the northeastern quarter of the continental U.S. The evolution of the pattern from April 26th-30th should ultimately dictate how much below temperatures finish the month in that area.
In terms of thunderstorms, activity has largely been below average. While there have been a few smaller-scale events from the Plains/mid-Mississippi Valley into the Southeast, 2014 continues to run near record low levels with respect to severe thunderstorms and tornadoes. Climatology says that even in slow severe weather early seasons (like 2010), activity tends to become more consistent by late April and early May.
