US Weather Commentary

"Fast & Furious" March to bring enhanced Spring clashes of Snow, Thunder and Flooding

An abnormally high National Snow-Cover (currently 44% compared to 22% last year) has set the stage for a mix of chilly March days and nights when hit from the North by the remaining Canadian Polar reserves for the first half of the month, while increasing the potential for flooding as warm air builds in from the South during the middle to latter portion of March. Spring rains can often be intense from the typical clash of late Winter remnants and early Spring surges, but with the North colder-than-normal and the South warmer-than-normal, the air mass collision and storm intensity are that much greater. Concerns include colder and snowier than expected outbreaks early on in the North, higher risk for flooding from Spring rains and snowmelt later in the North and Central regions, and increased risk of Severe Thunderstorms and Tornadoes in South.

REGIONAL WEATHER BRIEFS:

NORTHEAST:

Continue to remember that Canadian cold waves diving down West of the Mississippi sometimes trigger a "See-Saw" reaction, with southerly advection pushing some milder air up across the East for 24-72 hour increments.  Despite these undulations, this quadrant of the Nation will remain one of the more consistently Colder-than-Normal with a few snow and ice events in the weeks ahead.  As models continue to struggle with high-latitude blocking, surface Low tracks and associated cold air advection, expect to see a lot of last-minute revisions from short-term forecasters as anticipated normal days wind up being colder, and some rain events wind up being ice and snow events in the coming days and weeks.

SOUTHEAST:

The Southeast will continue to see undulations between warmer periods as the Spring Sun takes a greater role, and occasional cooler days from periodic Polar Plunges. Mobile, Al is a nice demonstration of his, which after hitting 20's last week and 70's and 80's this week, will chill back off to low to mid 30's early next week before rebounding back to 70's and 80's later this month. The enhanced southern stream will ease later this month, allowing sunshine to dominate, but strong thunderstorms and severe weather will remain a concern.

NORTH-CENTRAL:

Another Winter Storm is affecting the North-Central region as Blizzard Warnings currently stretch from South Dakota through Minnesota and Iowa, and Winter Storm Warnings span most of the Northern-tier, from North Dakota to Michigan.   The region will gradually become divided as we enter March between cooler & snowier weather [approximately East of the Mississippi River], and the Northern/Central Plains which will become more consistently mild due to ridging, rapidly eroding snow-pack, and some Chinook/Rockies down-sloping winds with corresponding compressional warming. 

SOUTH-CENTRAL:

At the cross-roads of many different air masses and storm tracks, temperatures will continue to ride a roller-coaster of fluctuations over the next week, and the southern Rockies have been experiencing some of the biggest temperature pattern increases over the course of February, as the Western Ridging finally expanded across the Rockies and into the Plains. Rainfall levels have been sparse over the past few weeks, increasing concerns for a Spring and Summer Drought. Dallas, TX only registered 18% of its normal Precipitation for the month of February. Today, high winds and low moisture levels have triggered Red Flag Fire warnings across much of Texas, demonstrating the seriousness of the situation.

NORTHWEST:

Temperatures across Northwest and northern-Rockies rebounded to Above Normal levels for most of February, but this has recently cooled off.  With a recent phase-reversal of the PNA pattern from positive to negative, troughiness and more storminess should be ushered into the region, as we head into March, with cooler (Below Normal) afternoons for the entire region the most noticeable thermal result this week.  The vast majority of this precipitation will be dumped and concentrated within 100-150 miles of the Pacific shoreline,  so milder temperatures should quickly re-emerge for inland zones. Later into March, the PNA is expected to trend towards neutral and relieve the region of the unsettled weather.

SOUTHWEST:

While the southern drought/fire risk areas will not be helped out very much, central & northern California (as well as the Sierra Nevadas) have recently experienced some Pacific rain-storms and hefty mountain snows, with another round likely next week.  Subsequently, cooler (Below Normal) days coupled with slightly milder nights will be a common theme next week across the region, wherever clouds and precipitation are most prevalent, but this should ease by mid-month as the PNA trends from negative to neutral.

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