US Weather Commentary

Spring temperatures pervade Nation as March heads out like a Lamb

However, Winter should make a Northern encore with some anomalous HDD's, wind, and even Snow & Ice, during first-half of April.

Relief has finally arrived to the Eastern States this week via gradually warming temperatures arriving from some of the consistently very warm Western & Plains States. The emergence of Spring-like weather (in synchrony with the Calendar) will be pleasant, but we continue to caution that Northern & Northeastern States remain vulnerable to anomalous Winter-like episodes wrought by an increasingly negative AO pattern, during the first 2 weeks of April 2007

But Spring storminess concludes "Fast & Furious" March 2007 like a Lion

March 2007 continues to impressively produce both anomalously large Heating Degree Day tallies simultaneously with anomalously large Cooling Degree Day tallies (across the South & Southwest), so when those air masses clash, sparks fly, and the result is over 275 preliminary U.S. tornadoes in 2007 to-date, above the average we're supposed to have through May 1st! In other cases the severe weather is taking the form of concentrated downpours & flash-flooding events (via Mesoscale Convective Complexes) from Mexico up across the Plains.

But this often does not translate into regionally widespread saturating rainfall (or the ground can not absorb downpours that fast), and as a consequence, drought continues to evolve over several States from the WesternGulfCoast to the Mid-Atlantic.  Across the Southwest, 90-100°F temperatures have been the result of subsidence and compressional warming, which only further dry out the air columns and fuel the forest/brush/wild fires.

On Tuesday April 3rd, ColoradoStateUniversity is scheduled to issue their first Hurricane Season Forecast of 2007 which will undoubtedly garner media, public and industry attention.  Below is our best estimate of the key numbers they will declare (along side historical averages), to help you prepare for any impacts they may cause:

REGIONAL WEATHER BRIEFS:

NORTHEAST:

High Pressure, warm air advection and longer days are gradually helping usher in much more Spring-like weather for this concluding week of March 2007 (which the Northeast has already clinched to be colder than normal for the month as a whole).  Further up across the Canadian-border communities and in New England, the unseasonably hefty snow/ice pack has been a powerful retarding force, preventing anomalies from getting too large and helping chill things off at night (Northeast fell to mid-20's Monday Morning).  As we advised 10 days prior to the pre-St. Patrick's cold/snow/ice event, we are equally concerned about another wave of Wintery weather yet again swinging through this region of the U.S., approximately April 5th - April 15th. Reminiscent of 2003, 1983 or 1982, please realize that Winter can still pack a wallop of cold, wind, snow and ice beyond April 1st, if and when hemispheric tele-connections and synoptic storm tracks tap into remaining Arctic & Polar air masses remaining in Canada.

SOUTHEAST:

At this point the Southeast U.S. is almost completely immune from Polar air masses that may swing through further North, but cloud-cover can definitely place a cooler lid on afternoon temperatures.  Ridging, sunnier skies and a lack of precipitation will help the entire region conclude March on a very warm note, as has been the case for much of the month.  From Mississippi to North Carolina, from Florida to Tennessee, the moderate drought we have been monitoring, is becoming increasingly widespread and severe, which could play a large role in Spring and Summer temperature outcomes.

NORTH-CENTRAL:

Pleasantly warm weather remains intact across the entire Mid-West this week concluding what now has become a generally mild March.  Due to some latitudinal thermal contrasts some noteworthy thundershowers, rainstorms and even severe weather outbreaks remain a concern across the Plains this week.  We are equally concerned about yet another wave of Wintery weather again swinging through the North-Central U.S., just as the Calendar turns to April.

SOUTH-CENTRAL:

As we conclude March, this region of the Nation starts to become increasingly reliant on strong solar radiation to boost temperatures to above normal levels, and logically the sunnier days will generally be the warmest, and the cloudier/rainier days will be the coolest.  Storm tracks, severe weather outbreaks and the most substantial cumulative precipitation (via MCC's) will focus on Central Texas and further North into the Plains (as the thermal gradient shifts poleward).  This once again exposes New Mexico and Louisiana to emerging drought, where despite some severe storms, remains either dry or unable to properly absorb heavy rainfall in a short time period.

NORTHWEST:

A cloudier but warmer pattern for inland sections and a wetter & cooler pattern for coastal sections continues on, as the vast majority of Northwest-focused precipitation is contracting further  (now mostly concentrated within 75 miles of the Pacific shoreline).  While this adds an exclamation point to the cumulative precipitation tallied by Seattle & Vancouver 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.  Further East, the Northern Rockies will endure some upslope Spring snows and winds this week as a result of the convection driving up into the High Plains.

SOUTHWEST:

Outside of a recent upper-level Low, probably the most consistently dry & balmy weather across the entire U.S. over the past few weeks, unusually large numbers of Cooling Degree Days have even been tallied this month (many cities were a significant 10-15°F Above Normal for a 10-Day stretch). The Santa-Ana induced heat from earlier in the month is a thing of the past as the 2007 Sea-Breeze is, and will be, a powerful cooling mechanism for coastal communities. However, the Warm-Dry-Warm-Dry positive feedback cycle looks to have a tight grip on most of the region as we head into April.  Unfortunately, this is also exacerbating drought and wildfire risk across California, Nevada and Arizona, joining their Southeast counterparts in these mostly sunny and dry patterns (but minus the severe weather).

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