September 13 Forecast Discussion- Tonight's Forecast

Tonight, we will be watching a system of rain move across the nation's midsection. The rain will be light to moderate, with probably some embedded spots of thunder. The Northeast will also have some rain to deal with this evening, particularly along the regions closest to the Great Lakes. This will come as a cold front swings across the area. The waters along the two east Great Lakes will be fairly warm with temperatures in the 70's at the surface. Temperatures in the air will be in the 50's, so it can be expected the lakes might enhance this storm activity. A high pressure system will be present in the Southeast, keeping the region nice and dry. Out west, in the Rockies there will be some shower activity with SNOW possible in the coming days.

Long Range GFS shows Squall Line for Midwest, Disturbance moving off Africa

Today's 12z and 18z GFS model runs show two things around the 216-hour time frame: A Midwest squall line (with heavy rains) and a disturbance moving off the coast of Africa.
Here's the 12z image, followed by the 18z image.

The 12z GFS is more trustworthy, as it takes in data documented by instruments sent up in the air that same day. The 18z and 6z runs don't have that gift, but the 0z and 12z runs of all models have that special backing that builds their evidence a little stronger.
The bad things about that, though, is the 12z image shows the squall line with heavier rains moving slower eastward, while the disturbance off Africa moves a bit faster than the 18z and appears to be slightly bigger.

Plains to suffer bone-chilling cold in coming days

The Medium-Range Ensemble Forecast members of the GFS indicate a frigid Canadian air mass will move into the Plains around September 15. Below is the GFS forecast.

Every forecast member shows a significant drop in temperatures coming in this week. The question is, where is this air mass now?

The circled region shows where the air mass is now. A sharp cold front will collapse into the country, with Canadian high pressure releasing frigid air as it drops down behind the front. Here's a projection of Thursday night's lows over the Plains.

TS Maria will go outto sea, TS Nate has made landfall and dissipated over Mexico last night.

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We have returned from a limited posting period, and we will be issuing detailed discussions starting tomorrow. For now, we have much re-organizing and data collecting to do.