The omega block has broken down across our region and the result has been a return to unsettled weather conditions. An area of low pressure is now crawling from the Mississippi valley into the Ohio Valley. This low pressure area will crawl at turtle speed across the Ohio Valley as the atmospheric traffic jam continues and eventually it will arrive in Maryland. Basically, as slow as the high was in position over us, it will be that slow for the low before a push to bounce this jammed traffic out occurs late next week. Gulf of Mexico and Atlantic Moisture should be able to stream into our region for the next few days, particularly Tuesday and Wednesday. Initially, through Monday, the features will be more scattered and it will hard to pinpoint the exact area for development…but more widespread rains are likely Tuesday and Wednesday when the flow will be most enhanced.
So far today there have been isolated and in-significant rain showers. The higher resolution modeling has done a much better job depicting the development of these rain showers. The disturbance zone responsible for today’s showers is slowly shifting northward. These showers may diminish as darkness approaches, but the impulse does try to intensify a bit. Region-wide, a chance of a few rain showers will be left in the forecast for tonight as conditions are such that a few more sprinkles or showers could erupt from time to time. There is a 10 to 20 percent probability of a thunderstorm.
For Sunday, the chances for scattered showers and thunderstorms look pretty good at this moment. There is probably greater than a 60% chance of showers and thunderstorms. I do see the potential for more organization and aerial coverage as the Sunday focal point will be stronger than the focal point that we have seen today. There should also be more instability in place on Sunday. Thunderstorms could very well be slow movers and they also will have access to some decent moisture to produce heavy rainfall. This raises the concern for potential localized flash flooding and excessive rainfall. Extensive cloudiness should limit the potential for severe weather to some degree. Any ongoing showers and thunderstorms in the morning would really limit severe weather. However, should there be some peaks of sunshine; a few severe thunderstorms could develop. The Storm Prediction Center has placed southern and western areas under a “see text” probability for severe thunderstorms within 25 miles of a point.
For Monday, another round of showers and thunderstorms is likely. The severe threat will be highly dependent on convective cloud debris and any potential ongoing action from the overnight. Hail and strong wind gusts appear to be the primary threats, especially if sunshine breaks out through the cloudiness. Any thunderstorm could contain localized heavy rainfall and they could be very slow movers suggesting localized flash flooding is once again not out of the question. There could be a little less in the way of activity on Monday.
For Sunday and Monday, while we do not have any flash flood watches in effect, I could see a few polygon warnings being needed. Sometimes, watches are not posted until the day of the event when there is higher confidence of the axis zone of organized development. History suggests the higher terrain influences, but it can happen elsewhere. The week of dry weather helped, but we are still running well above average in our basins with the wet spring season. Dover and Georgetown have been drier over the past 250 days and can absorb more rain. The main concern is the northern half of our area or north of the New Castle and Atlantic Counties.
The stationary system and frontal boundary makes the closest approach on Tuesday and Wednesday. With the flow most enhanced at this point and time, this is when the heaviest rainfall will occur and the most widespread shower and thunderstorm activity of this entire stretch. The flood threat will be highly dependent on how bad the damage is done on Sunday and Monday. However, folks living in low-lying areas, along creeks, along streams, and along rivers should be aware that quite a bit of rain could fall in some communities on top of what falls prior to this time frame.
Residual moisture and effects from this system appear to linger into Thursday and Friday. While the coverage will be less, showers and thunderstorms are still a possibility, especially during peak daytime heating. At this point, a new powerhouse storm system will be taking shape in the Western United States and shift into the Central United States on Saturday. We will probably experience our first precipitation free day on Saturday (of the next seven). A pretty nasty severe weather outbreak may take shape in the Central United States next weekend if all the ingredients can come together. This system could impact our region by Monday according to the latest long range guidance, although it may be slower in arrival overtime and further adjustments could place this system in our territory Tuesday or Wednesday.
Please remember to turn around and don’t drown if you see rising flood waters. Also, if you hear thunder, you are close enough to be struck by lightning. Move indoors immediately when you hear thunder.
After Midnight, we will provide an even greater outlook into the next few months. Probably within the next week or two, we will look in-depth at the hurricane season (although I put out a hint last weekend). Until then, keep the umbrellas handy!
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