Significant system D5-6, followed by cold.

The much hyped La Nina severe weather season will likely come in full force in the Midwest starting Tuesday with a strong upper level low diving south out of British Columbia. This potentially dangerous storm system will move east through the Ohio Valley and into the Mid Atlantic and Northeast by Saturday. It is uncertain what the effects will be on the northeast.

Confidence is high for a signficant load of Gulf moisture to advect into the plains states and Ohio Valley region out ahead of the trough. In question is how strong upper level troughing will be off the east coast. That will dictate how sharp the upstream ridging will become. The ECM is much more robust with ridging in the east than the GFS. Per the Euro, SNE could easily see 70 mid week. As it is, I am confident that Keene will exceed 60 degrees on Wednesday. High temperatures Thursday will be more dependent on cloud cover as a shortwave swings a cold front though in the early afternoon. The ECM brings the shortwave about 100 miles north of the GFS with 500mb heights about 6dm higher across Maine.

Thursday Night will be the break between storm systems. Clouds will move back in on Friday. Depending on the strength and position of the midwest storm system, we may see light showers throughout the day on Friday as the northern precipitation shield moves over the area. This is about what the GFS has in mind, however the ECM is further north and has the precipitation shield moving across southern Ontario and Quebec with a better chance of thunderstorm activity reaching SNE. By Saturday the ECM upper low is 12dm deeper than the GFS and about 300 miles further north. Regardless, it appears next Saturday could be a rather cold, wet, raw day in the northeast as the frontal boundary moves into the region. Of more importance is the potential for heavy rainfall on Saturday. The 00z GFS shows secondary coastal development during the day, tapping the copious amounts of moisture available. This could result in flood situation with widespread rainfall of 1 to 2 inches. However, it is still a week away so nothing is set in stone.

Following this storm system, 500mb longwave trough sets up over the eastern half of the country. -NAO / -AO signal is clear through the medium term, and will likely continue through the next two weeks. +PNA ridging may move in for the first time since February and will help out in an overall below to much below normal regime in the east through the 19th. However, storminess over the WPAC and China has been rather low recently and the progression of storm systems through the country will be greatly diminished by the western ridge, so in fact the entire country will likely be dry during this period. Considering high temperatures averaging between 40 and 45 and low temperatures around 25, there will be a chance of wintry precipitation with any weak shortwave that moves through.

By the April 21st, SE ridging will redevelop and warmth will return to the east starting with perhaps a brief period of above normal temperatures. Still appears storm activity will be low through the end of April. Once the -NAO /-AO feature breaks down, the flow will be generally zonal across the nation with normal temperatures likely through the end of the month.

Tropics:
Ridging has broken down over equatorial Africa, and the intertropical convergence zone now features a series of disturbances stretching into the eastern Atlantic. Westerlies are still active down to 10N in the EATL with the ITCZ located from 9N13W to the equator at 26W. Sea surface temperatures are above normal, so there isnt anything completely ruling out a tropical wave or two of interest by late April.