Shower Chances Rise Into Thursday Flash Flood Potential
Shower Chances Rise Into Thursday Flash Flood Potential
After three days of unseasonal cool weather especially this weekend we are seeing the upper trough off the East Coast beginning to weaken as a heat ridge on the Middle Mississippi Valley building east. It can only get so far because nothing in the Atlantic is moving. This is creating an unusual northerly flow ahead of a warm front that is forming to the west. Clouds are actually moving from north to south and you can see on the loop the brighter white higher cloud tops with rain are actually moving southward from Eastern Canada.
SATELLITE
WEATHER RADAR
Rain from those clouds is showing up on the regional radar and it won’t be long before that rain with embedded heavier downpours lines up and down the Hudson River in New York state and then makes its way southward. Look for clouds to increase today and then keep an eye on the radars as the rain advances southward in a narrow band, eventually working its way through New Jersey.
Winds will be turning to the southeast today and over the next few days which will help feed in some moisture. It will also impact high temperatures as will the cloud cover and eventually the rain. Showers will hold off to the middle or late afternoon so that will allow highs to reach the mid to upper 70s in most places however to the west of the frontal boundary, mainly west of I-81 in Pennsylvania and points south, highs there will be in the 80s.
We will see showers overnight taper off by morning but do bear in mind as the model loops show, that the rain is in a relatively narrow band about 100 or so miles wide so if you are on either side of that strip of rain, you may not see much. Wednesday will be a cloudy day but the frontal boundary remains and that will start to generate another round of rain for Wednesday night and Thursday.
This second round of rain has the potential to be more robust and the Weather Prediction Center is indicating a marginal to slight risk of flash flooding for areas in Eastern Pennsylvania to Southern New England (5 to 15% chance). The problem in forecasting rain amounts in a situation like this is the large variability of rain, the convective nature of this, and where are the east west boundaries.
We also have models still not lined up together with some further east and other further west. The best approach remains to emphasize the risk for a few inches of rain from Eastern Pennsylvania to Southern New England and just wait for the radars to set up later today. This rainfall forecast from the European model is cumulative through Thursday.
Once again temperatures will be impacted by clouds Wednesday and an ocean wind. Highs will be in the 70s east of the frontal boundary (in red) and 80s to the west. This also sets up severe weather risk for later Wednesday and Wednesday night with a marginal risk reaching New Jersey and the Hudson Valley west of the Hudson River and a slight risk in Pennsylvania mainly west of I-81.
Rain lasts into Thursday and then as a wave develops on the front the rain should pull out later in the day or Thursday evening. Highs will be in the 70s to near 80. Then we dry out for Friday and I think the weather overall will be rain free through the weekend, though there could be a scattered shower or thunderstorm Saturday and Sunday mainly inland. Highs each day will be in the low to middle 80s with 70s along the immediate coast. A stronger cold front arrives next Monday with showers, thunderstorms, and the potential for severe weather risk.
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