Troughs Become More Prevalent In Eastern US Towards May!

In yesterday’s and even other recent posts i’ve been showing you the greater liklihood of seeing troughs back into the East and hanging there, starting this weekend as the storm that’s sliding across the country pulls the trough in. If you live anywhere from Washington DC up to New Brunswick, make the most of the current warmth, this may be a last decent spell of late spring warmth for a while.

Here’s what I showed you yesterday.

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The pattern is now going to the negative NAO/AO, positive PNA state and one must watch for late April frosts and freezes pretty far south into the East as models show a deep Eastern trough late month. Here’s the ECMWF vs GFS in the 8-10 day means.

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Here is the mean 500mb heights in the 8-14 day, clearing showing the Western US and Greenland ridges indicative of the +PNA/-NAO which leads to a substantial trough into the Southeast with a feed of chilly air all the way from a still cold and snowcovered central Canada. With Hudson Bay still frozen over and the amount of snow still up there, any trough with a NW flow, will present much cooler spells compared to normal over the Great Lakes and East compared to normal and it’s worth paying attention to that if your a gardener.

NAEFS_zdns_d264_00

Here’s forecasted temperature anomalies between April 25 through May 1. The ridge and heat is going right to where the driest soils are and so as we press deeper into spring, one would expect that area of heat to expand eastwards through the Rockies once we seeing drying take place in coming weeks, where the snows are now. In other words, it’s once this stormy spell in the Rockies ends, it won’t take long for this to dry out.

poeabn_h264_00

Here’s the latest CFSv2 for weeks 3-4 or looking out through the first half of May.

What’s interesting is that this model is beginning to show warmer in the East by week 4, however that doesn’t mean more troughiness or cooler weather in the West but perhaps indicates more of an eastward expansion of the western high.

wk3_wk4_20130416_NAsfcT

If we look at week 3-4 precip, there is a drier period coming up for the East as the trough drives cool, dry Canadian air into the East, also notice the lack of moisture in the West. The good news is that we’ve seen significant spring snows in the Rockies and this will certainly be a help, however, it doesn’t take long for dryness to return in this region especially once that ridge returns and is will do from this weekend on. The real concern is between coastal California and Salt Lake City, this region is very dry and with no appreciable rainfall over the next month or so, this is where your ridge is going, setting the stage for a long and hot summer in the West.

wk3_wk4_20130416_NA

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