The southern states from Texas through North Carolina (with the exception being Florida) have been experiencing many rainy days through the second week of March. Some places in the deep south have had measurable rainfall for 6 days straight. Below is a seven day long accumulated precipitation map for the U.S.

7 Day accumulated QPF

This will be the last gloomy forecast day for the southern states for the rest of the week. High pressure will be in control of the eastern seaboard and provide a nice stretch of weather until a strong cold front barells its way southeastward through the eastern third of the nation during the day Thursday. The cold front will be accompanied by showers and embedded thunderstorms and will usher in some unseasonably cool air for Friday.

The Pacific Northwest is next in line for the long period of unpleasant weather. Valley rain and mountain snow are the story today and will be for the next few days. The overall pattern heading into the upcoming weekend looks to be troughiness digging into the western states with several impulses riding through, while a large ridge begins to build across the central states supplying sunny skies and above average temperatures for those locations.

The tale of two weather stories may be seen as we look at the satellite/radar composite. This map is valid at 13Z (9am) for March 13, 2009.

Areas of high pressure are in control across the northern states supplying brilliant sunshine and a pleasant spring day for many. The overall upper-level pattern consists of split flow with the Polar Jet streaming north of the U.S. and into Canada while the Sub-Tropical Jet (STJ)  is easily distinguished on this map and can be seen moving through Mexico and through the Southeast States then off of the Mid-Atlantic coast. The moisture-laden STJ has several impulses riding along it which are spawning all of the showers and thunderstorms you see on the map. An upper-level cut off low spinning in the Southwest States was the culprit for an outbreak of strong storms last night and is forecast to eject ENE through the Southeast states through the day Saturday. This will keep the southern states unsettled until the system spawns a surface area of low pressure which will track off the Mid-Atlantic coast Sunday Morning. Areas of the Mid-West and Northeast should be spared as the aformentioned area of high pressure should suppress the area of low pressure and its associated rain showers to the south. Most of the country stays dry after that storm with the exception of the coastal Northwest as the Polar Jet makes a return in a extremely zonal progressive flow shaping up for next week.

 So much for the high-amplitude short-wavelength March pattern I was hoping to get into. If you don’t like stormy weather, this pattern is for you!

A broad area of low pressure currently moving northeastward through Iowa is dealing the central states with a cornacopia of weather and as strong of a thermal graident as you will see. The northern side of the storm ecompasses a raging blizzard in the Northern Plains with gusty winds and sub-zero temperatures. While temperatures out ahead of the storm approach record warmth and temperatures climbing into the 80’s in some localtions from the Gulf States up to the Central Mid-West before strong thunderstorms fire up along a cold front that will pass through these areas and begin their cooldown to more seasonable levels. As the storm strengthens and pulls away into Southeast Canada, the ridge supplying the pleasant weather across the east will begin to break down and the pattern will become more zonal for Thursday. This will bring a return for more seasonable temperatures across the CONUS as most of the country remains dry with the exception of the Gulf States through Friday. The Sub-Tropical Jet becomes active with a southwest cutoff and creates an overrunning precipitation event for the east coast Sunday night into Monday.

The continental U.S. stays free of any major storms through today. An upper-level trough begins to dig into the Pacific Northwest providing the ski resorts of the intermountain west with cool temperatures and snowfall. A weak area of low pressure will ride just north of the Great Lakes and into Southeast Canada today, bringing with it overcast skies and possible light mixed wintry weather from the Great Lakes stretching into central and northern New England. An area of high pressure moving off the east coast will usher in a warming southwest flow from the Southern Plains all the way up to New England. Texas will warm well into the 80’s as the warmth will also be felt into the Ohio River Valley with temperatures in the 60’s.