Weather Update: Sunday – April 28, 2024

WDEF-TV News 12 Weather Forecast

WDEF-TV News 12 Forecast Discussion

The News12 viewing area has enjoyed some pleasant weather for the past few days, as the west through east motion of the atmosphere has slowed down to a crawl. The prolonged period of dry weather is due to the development of a highly amplified jet stream pattern in the upper levels of the atmosphere; around 20 to 40 thousand feet. An upper level, long wave trough has formed along the Pacific coast of the United States. In response, an equally amplified (strong) upper level ridge developed over the eastern half of the nation early this weekend. These types of patterns are relatively common during the Spring season as the battle continues between the polar region and the equator for air mass dominance in the middle latitudes. It is also common that the active weather part of these patterns, including the lengthy corridor of showers and thunderstorms, shifts very slowly east, ahead of a moderate to strong, cold frontal boundary.

This weather scenario will keep the Tennessee Valley and Southern Appalachian region dry again today and Monday, as the upper level ridge axis ambles along from the Appalachians this morning, to the Eastern Seaboard by Monday evening. Additionally, a massive surface high will extend southwest through the western Gulf of Mexico until Monday morning, which will limit the amount of low level moisture available for thunderstorm development throughout the daytime hours. Finally, by late evening or very early Tuesday morning, enough atmospheric moistening will have developed ahead of the once powerful, Plains frontal system, for the development of showers and a few thunderstorms. We are still a day and a half away from this precipitation event, and some changes are still possible, but at this time it appears that the showers and thunderstorms will move across the News12 viewing area, around midnight late Monday night into early Tuesday. Some of the models indicate a relatively short-lived period of precipitation with the area of rain exiting through the western Carolinas by late morning, while others keep a chance for some trailing showers and thunderstorms through early evening.

The most newsworthy aspect of this event is that it appears that we should not be concerned about severe, or even moderately strong convection with this frontal passage. One of the main components of severe thunderstorms is wind shear, including both the physical structure, in terms of directional wind changes from the surface into the upper levels of the atmosphere, and of greater importance, the speed of the wind. The other component necessary for any thunderstorm regardless of strength is at least some atmospheric instability, which includes sufficient moisture and heat energy in the lower levels, with colder and slightly drier air aloft. The good news is that the powerful wind energy associated with the historic Plains severe weather event over the past couple days is modeled to pass well north of the viewing area, before the line of showers and thunderstorms arrives. Concerning the availability of thermodynamic instability, or convective available potential energy (CAPE); computer models are showing very little CAPE in association with the frontal passage late Monday night into Tuesday. Of course, late night thunderstorms are weaker than afternoon and early evening convection, due to the loss of solar energy in the cooling night time air.

One common theme for our forecast over the next week is warmth. Computer model guidance indicates that both high and low temperatures will be a good five to ten degrees above normal throughout the week, as the dominant flow will remain southerly through most of the week with a brief period of weak northerly, low level flow Tuesday night through Wednesday night. We will have another opportunity for rain at the end of the week. Showers and thunderstorms are modeled to develop over the area Friday through Saturday, ahead of a slow moving, frontal system. If all goes well, there may be a break in the action on Sunday, allowing us to enjoy at least one dry day over the weekend.

Stay tuned to our forecasts throughout the week, to keep track of any strength or timing changes to this week’s frontal systems. We are still not in any significant trouble in terms of annual precipitation. Our annual deficit is around two and a half inches but evaporation rates continue to rise as we move further into the warm season. Hopefully we will have a few opportunities to pick up some spring time rainfall before the intense heat of summer begins.

The Climate Prediction Center 8-14 Day Outlook for Sunday, May 5th – Saturday, May 11th, features above normal temperatures and above normal precipitation during this period.

National Drought Summary for April 25, 2024

Summary

Moderate to heavy rain amounts fell across parts of the Southeast and Northeast this week, leading to localized improvements to ongoing drought and abnormal dryness in the Southeast, and mostly unchanged conditions in the Northeast, aside from western New York, which missed out on the heavier precipitation and saw minor degradations.

The central third of the contiguous U.S. saw a mix of improvements and degradations, based on where heavier precipitation did or did not fall and where dry and windy conditions continued. Parts of Illinois, Indiana, Ohio, the Michigan Lower Peninsula, southern Missouri and southeast Kansas saw improving conditions after heavier rains fell there. Meanwhile, moderate drought expanded in northwest Missouri and portions of west-central Wisconsin, Minnesota, northwest Iowa, the far southern Michigan Upper Peninsula and far northeast Wisconsin. Much of Texas remained the same, with a few degradations in the southeast corner and several degradations in central and southern Texas where long-term drought conditions are still causing impacts. Recent dryness and warm and windy weather in northwest Oklahoma and the Texas and Oklahoma panhandles led to abnormal dryness developing there.

Short-term dryness and high evaporative demand led to large areas of degrading conditions in northeast Wyoming, while west-central Wyoming, north-central Colorado, northeast Utah, western Montana, and the northern Idaho Panhandle all saw areas of improvement due to lower evaporative demand and improving snowpack recently. In Hawaii, an active trade wind pattern continued, leading to some improvements on the windward (northeast) slopes of the Big Island and Kauai, while a small area of moderate drought developed on the leeward (southwest) portion of Kauai. In Puerto Rico, a few improvements were made where recent rainfall has improved streamflows and crop stress, and lessened rainfall deficits and raised reservoir levels.

No changes were made to the Drought Monitor this week in Alaska.

– NOAA National Centers for Environmental Information

https://droughtmonitor.unl.edu

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