This Workweek's Chances for Rain
By Erica Grow on July 8, 2012, 10:28pm
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After a dry and beautiful start to the workweek, the threat for thunderstorms will come back by mid-week. But who gets the rain, and when? Those details have been challenging to fine-tune in the StormTeam8Day.
The map above shows a stationary/cold front a couple hundred miles to our south. This is the same front that moved through on Saturday, bringing some showers and storms. You can also see an area of high pressure centered over the eastern Great Lakes, and a weak area of low pressure just barely to the west of this high. These are the features we'll be watching this week, but the most predominant one is the stalled frontal boundary to our south.
The models are in agreement that the high pressure area maintains control of New England tomorrow, so the Monday forecast looks great with lots of sunshine and a light breeze from the northwest continuing to keep the dewpoints low. The models are also in agreement with a trough in the jetstream digging into the western Great Lakes region on Tuesday, where it will remain until Thursday. The upper-air tilt, therefore, will become southwesterly, and the models indicate that we will tap into some of the energy from the Subtropical Jet by Wednesday. A weak line of PVA (positive vorticity advection) leads to an isolated shower on the NAM (QPF values of 1 or less in Connecticut), but the GFS has shown liquid equivalents around .25" in northwestern CT through western MA for 2 days in a row now. I think the GFS is picking up on the potential for that weak low in the Wisconsin/Michigan area (see map) to touch off a shower or storm. But as you can see on the map, the disturbance isn't producing any rain right now, so I am keeping our forecast dry for Tuesday.
The models keep CT dry for the most part on Wednesday and Thursday, but the GFS shows a very pronounced vorticity maximum along with a shortwave trough moving through New England on Wednesday. If this vort max moves through as progged on the GFS (the Euro has the vort max further to the north), then I believe it will trigger a couple thunderstorms.
The most significant threat for rain will be late in the week. The models have been consistent in pushing a line of vorticity (the stalled frontal boundary) northward into Connecticut on Friday, though they have not been consistent in giving us appreciable rain out of that system. But again, with summertime temperatures and humidity in place, I see no reason to doubt that we'll get a few showers and storms out of this disturbance.
Overall, it looks like a fairly dry week, with a couple chances for beneficial rain!
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