PM Forecast Discussion- Heavy Rain Tonight
By Erica Grow on April 22, 2012, 7:52pm
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The April Nor'Easter is panning out exactly as we expected so far. We had some light showers before noon in parts of the state, then the rain turned steady in the afternoon. So, the prediction for heavy rain to move in tonight seems to be right on track. The lowest storm total comes to us from GFS, which is only predicting about 1.75" by 12Z Monday. But the NAM is going with 2.5" during the overnight, and the Euro has at least 2", maybe a bit more, by 12Z Monday. The intense rainfall could lead to flooding in small streams and creeks, because they can reach bankfull much quicker during a heavy rainfall than rivers can. Our local rivers will be just fine, since it's been so dry.
The NAM still has the potential for a couple showers Monday afternoon, but GFS and Euro are dry for the rest of the day after 12Z. Then, the 540 thickness line presses eastward on all model data as the core of cold air moves through New England with this large synoptic trough. The Euro has the most moisture during this timeframe, and according to this model, we could see a coating of snowflakes in the highest elevations of CT. I do think it's too warm for any snow to stick, though, as temperatures haven't even been below 40 degrees, let alone 32 degrees, in at least a week. So I think we might see some snowflakes fall, but they'll melt immediately when they hit the ground.
The upper trough finally moves out on Wednesday evening, but another trough quickly follows on GFS. The secondary jet trough moves in late on Thursday's GFS data, with a few showers before 0Z Friday. The Euro also has a chance for showers, but the trough isn't as pronounced. The chance for showers lingers on the Euro into Friday, though there isn't a lot of moisture with this weak disturbance. The overall mid-level flow pattern turns zonal for the weekend, and the jet stream is progged to be over Connecticut and New York on GFS. A few vorticity maxima are showing up on the model data along this jet streak, which could lead to a shower or storm as temperatures warm back to around +10C at 850mb. The Euro also shows a weak disturbance moving through on Sunday with a few showers, but the GFS has this same weak disturbance on Saturday. Neither model had any rain for the weekend on yesterday's grids, so I kept it dry for now. Maybe I'm being optimistic, but with all the rain we're getting right now, I'm hopeful we'll stay dry next weekend!
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