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Wednesday, 11:30 a.m.
An upper-level trough and a surface cold front are combing to push moisture off the Eastern Seaboard at this hour, though the drying-out process will be rather slow across a good chunk of New England. Still, the end result will be a stable weather pattern from New England into the Carolina heading into the final weekend of spring.
Meanwhile, in the Rockies, the weather remains dry, and there's not much in the way of meaningful rain in the areas that need it worst, portions of New Mexico and Colorado where wild fires continue to rage out of control.
If you look at the jet stream, it is a rather convoluted pattern these days. There's no 'typical' dominant upper-level ridge somewhere that is promoting a heat wave. We'll end up with areas of heat in the coming days, one over the central and eastern Rockies out into the western Plains, and another this weekend and early next week from portions of the Midwest into southern Quebec, but that's not how you normally diagram it. Look at the 500 mb forecast for Saturday morning off the 12z NAM:
That's just not a 'normal'-looking jet stream pattern! You have the remains of an old upper-level low way out in the central Atlantic that will gum up the works for systems progressing any farther off the East Coast the rest of the week. In fact, the system now sliding off the coast will end up taking the path of least resistance, which ends up being a south relocation to off the Southeast coast! A ridge will extend northeastward over the top of these features through the Great Lakes into southern Quebec, but it turns the flow onshore, or at least with an easterly component to it, all up and down the Eastern Seaboard. Then you have an upper-level low trying to bury itself over northwest Mexico and the eastern Pacific, a feature that may break some serious heat into the Bay area this weekend, just in time for the U.S. Open to be played.
The tricky part of the forecast will be from the Northwest to the Midwest, as a series of upper-level disturbances will fly through these areas in the coming days. Despite a limited amount of moisture available to these features, there will be plenty of contrast to the heat south of the main jet stream vs. the cooler air underneath the jet that some showers and thunderstorms are bound to form in conjunction with the approach and passage of any individual feature.
What's tricky about it is WHO gets the rain, and how much. How far south does any front push? That's a critical question, because a front that gets far enough south could have the effect of turning the wind into an upslope flow over the eastern Rockies. That means moisture, and that's a wonderful thing right now in Colorado and New Mexico! And the models are suggesting it's not going to be dry.
The first of these features will dart across the northern Plains late this afternoon and tonight with some showers and thunderstorms, with those thunderstorms potentially becoming severe at some point tomorrow as they march into Minnesota.
That same feature will push a front down into Nebraska and Kansas with some thunderstorms, and there's some cautious optimism it may moisten up eastern Colorado tomorrow night. However, that feature will quickly fade, and another will approach late Friday and Friday night through the Northwest into the northern Rockies. Once again, another cold front generated by this trough will press out across the Plains Saturday, and down the Front Range of the Rockies. If the 12z NAM forecast for Saturday afternoon is to be believed, then there's a more reasonable chance of desperately needed rain in the fire-ravaged areas. But that remains to be seen. After that, moisture will be hard to come by for these areas.
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