Spring and (More) Severe Weather Coming: Mark Your Calendar

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If we could rewind the calendar to last week we’d find ImpactWeather’s StormWatch team contemplating a severe weather outbreak across the Plains and the South. In fact, I blogged about it last Tuesday (“15 Inches of Rain at Our Water Cooler“) and we even featured the pending outbreak when we hosted our ongoing severe weather webinar series last Wednesday. All of that was for a system that brought flooding rains, severe thunderstorms and tornadoes to the Plains and upper Gulf Coast Thursday, Friday and Saturday. Previous to that, on March 2nd, I wrote about the severe weather moving through the Tennessee River Valley that had started two days earlier with deadly tornado outbreaks in Harrisburg, Illinois.

Lifted Index for next Tuesday. Positive values indicate a stable air mass, negative values indicate an unstable air mass. Unstable air masses are responsible for thunderstorms — the more unstable, the greater the risk of severe weather. Click for larger image.

Now once again, severe weather indicators are pointing to a major severe weather outbreak early next week. This is a slow-moving storm system that is already pounding the West Coast from Monterey Bay, CA to British Columbia. Rainfall totals in some places approached 10 inches yesterday while computer models suggested that much and more for many areas, while snowfall could be 2-3 feet in the higher elevations of the Cascades. The strong winds are exacerbating the situation by toppling trees, power lines and 18-wheelers. It’s this same system that will eventually move across the Great Basin and the Rockies to the Plains by early next week.

Precipitable Water for next Tuesday. Precipitable Water is a measure of the moisture in the atmosphere that would be available to fall as precipitation. When PW values in Minnesota and central Canada are the same as the values over the Gulf of Mexico, it's a good indication that rainfall values could be unusually high. Click for larger image.

Already this week we’ve been witness to hundreds of record-breaking high temperatures — in some places 20 and 30 degrees higher than seasonal norms — across the Plains and Midwest. Even Rhode Island joined the ranks of record setters with a high of 72 degrees in Warwick. When considering the potential for severe weather at this time of year, that’s like placing your fully-loaded pic-a-nic basket on a campsite table in Jellystone Park: the trap has been set, now it’s just a matter of time.

By early next week the heat and humidity of the Plains will be equally as high as today — if not more so. When the cold front approaches it will be textbook severe weather as the colder, drier air clashes with the broad area of warmth and humidity. Widespread areas of severe thunderstorms (squall lines and strong tornadoes likely) along with heavy rainfall (2-4+ inches will not be uncommon) should be the result. Given the already-saturated ground in so many areas, additional and far-reaching flooding concerns will continue.

The GFS computer model targets northern Texas, eastern Oklahoma and southeastern Kansas as a focal point for severe weather late Monday/early Tuesday. Click for larger image.

Early indications this morning suggest the system will remain strong, while several models threaten to isolate the low over New Mexico and West Texas. A high-energy,  fast-moving frontal system with strong upper-level support can be responsible for strong squall lines containing more numerous and more active severe thunderstorms and tornadoes.

Long-range forecasts should always be treated with caution as things are always subject to change. Additionally, wild swings in long-range forecasts, as well as divergence between various computer models, is not uncommon. We’ll keep you updated over the next several days.

By the way, the first day of spring is next Tuesday, 3/20.  Looks like March is continuing as a lion.

 

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