US Weather Commentary

Pleasant thaw on tap for next week, but next Polar Air mass will dive down by St. Patrick's Day Weekend. Temperatures this entire week across several Northeast States have been registering an amazing 20°F-25°F colder than computer models had predicted just last week.  Coupled with some anomalous snow-cover and harsh wind-chills (not incorporated by Degree Day tallies), March 2007 has already made its historic mark on the Nation from the Plains to the Atlantic.  While the well-needed thaw keeps getting postponed for the East, it is already yielding pleasant temperatures over the Rockies, before gradually expanding into the Plains, Mid-West and eventually the Eastern U.S. next week. Outside of the Western and Southern U.S., these Spring-like temperatures won't be around for very long, as the next Polar air mass will dive into the North-Central U.S. about a week from today. This could initiate a new parade/sequence of colder Canadian air masses, along with some Snow & Ice events, that will rotate predominantly through the Mid-West and Northeast during this mid-March stretch.

{Note: Because our medium-range forecast periods are diluted by both the pending warmer days and colder transition, expect to see some larger negative anomalies in our tables next week for the 3-5 Day and 6-10 Day periods}.

Volatile, "Fast & Furious" March also igniting severe weather at record clip

Phenomenal (North-South) thermal gradient producing frequent cyclogenesis, wind-storms, and tornadic outbreaks. March 2007 has impressively yielded anomalously large Heating Degree Day tallies simultaneously with anomalously large Cooling Degree Day tallies (in the deep South), so when those air masses clash, sparks fly, and the result is over 175 U.S. tornadoes in 2007 to-date (well ahead of the average we're supposed to have even through April 1st).  But severe weather often does not translate to widespread saturating rainfall, and as a consequence, drought continues to evolve over several States across the South.

Tele-Connection phases and combinations to sustain transient West-to-East flow

Following a 2-week run in a negative phase, the PNA Teleconnection is returning back to a Positive/Neutral Phase, which has predominated the entire Winter.  This is bringing an abrupt end to the Southwest's brief flirtation with Winter storms, and focusing precipitation back towards the Pacific Northwest, but still concentrated mostly along the coastal zones.  This shift in the Pacific flow, will only worsen some main regions of severe drought:  (1.) Southern California/Arizona ; (2.) Western Plains/Wyoming; (3.) Southern Texas/Rio Grande Valley; (4.) Florida Peninsula.  Furthermore, Pacific flow is generally mild by nature, and when traversing over the Rockies, subsides, compresses and warms further.

REGIONAL WEATHER BRIEFS:

NORTHEAST:

Minimum temperatures in the lower-Teens for several mornings, even within the big cities, is something that would garner attention even in January, let alone a week into March.  Despite these undulations, this quadrant of the Nation is indeed remaining one of the more consistently Colder-than-Normal regions through the first 10 days of March.  Some welcomed, Spring-like temperatures are on tap for next week, but that may come crashing to a halt via a Wintery St. Patrick's Day weekend. 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 (as we saw last Friday/Saturday).

SOUTHEAST:

Stronger Spring solar radiation helped boost Miami to a record high of 90°F last Saturday, but the recent trough and come cloudiness are bringing things back closer to Seasonable levels for the Southeast.  After a brief storm outbreak the 11th-13th, generally Seasonable to Warm temperatures and drier weather will prevail thereafter.  Evolving drought and wildfire risks need to be monitored with extra vigilance in the weeks ahead.

NORTH-CENTRAL:

The last Blizzard has further built-up the snow pack across the Upper-Mid-West and Great Lakes regions, where temperatures again remained 10°F-20°F Below Normal yesterday, epitomizing the Arctic grip for the early stages of March 2007.  Flow from the Pacific and substantial Down-sloping winds from the Rockies will finally eat away much of this abnormal Plains snow cover, and where the ground is already bare will help boost temperatures to incredibly nice Spring-like levels (such as breaking 70°F in western Nebraska and western South Dakota).  On February 21st 1918, Grandville ND sky-rocketed from -33°F to 50°F in less than 24-hours(!), so folks in these parts understand the power of subsidence and Chinook winds at the end of the Winter Season.  Closer to the Upper-Mississippi Valley & Great Lakes this thaw should be abruptly ended by another round of Polar air, ice and snow ahead of the St. Patrick's Day Weekend.

SOUTH-CENTRAL:

The roller-coaster of temperature swings has finally coming to an end with a rather consistent Warm/Dry pattern setting up. While severe weather always needs to be anticipated at the base of "Tornado Alley", such storms often do not translate to widespread saturating rainfall, and as a consequence increases concerns for a Spring and Summer Drought [Dallas, TX only registered 18% of its normal Precipitation for the month of February].

NORTHWEST:

A cloudier but warmer pattern for inland sections and a wetter and cooler pattern for coastal sections is taking shape as the vast majority of Northwest-focused precipitation will be dumped and concentrated within 100-150 miles of the Pacific shoreline.  While this adds an exclamation point to the cumulative precipitation tallied by Seattle since October 1st, it does little to help inland/mountain hydro-electric areas across Oregon, Idaho and Northern California/Sierras which will likely portend to a Spring stream-flow only 50-90% of Normal.

SOUTHWEST:

Probably the most stable, dry and pleasantly balmy weather across the entire U.S. in the days and weeks ahead, whether it's breezy highs around 70°F for coastal L.A./San Diego, temperatures pushing 80°F in Fresno CA, or some toasty 90°F readings in Phoenix, Tucson, and Palm Springs CA.  Unfortunately, this is also exacerbating drought and Wildfire risk across the region, joining their South-Central and Southeast neighbors in this mostly sunny and dry patterns (but minus the severe weather).

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