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Beautiful weekend, potential showers and thunderstorms next week

Most of us are currently enjoying a beautiful Friday afternoon, with scattered clouds and sun, and temperatures in the mid to upper 70s, as well as low humidity. Some of these scattered clouds, however, are of the cumulus variety, which are very well illustrated by the current satellite. Given our relatively unstable airmass from an approaching cold front, there is the chance that some of these cumulus clouds will turn into a few scattered showers and thunderstorms for this evening. Fortunately, most of us will still have a couple more hours of dry weather before having to worry about any of this, and a lot of areas may not see any rain at all, but it may be a good idea to have an umbrella if you are going out tonight.

Rest of tonight and Saturday: A cold frontal boundary that is helping to trigger these showers will eventually move through tonight, giving us an area of high pressure, and dropping our temperatures into the mid 50s. It will also dry out the weather even more, as dewpoints will fall into the 40s. For tomorrow, we can expect sunny skies, and very low humidity values, and temperatures in the low to mid 70s. There will be a bit of a stiff northerly breeze at times, so it may be tough to play outdoor basketball or keep a blanket sturdy for a picnic, but overall the weather looks great. A few cumulus clouds may develop in the afternoon, which may make it feel a tad cooler at times during the afternoon.

Saturday night and Sunday: As high pressure continues to build in, winds will lessen, and clouds will continue to clear. Given the already very dry airmass, this will allow temperatures to rapidly fall, via ideal radiational cooling conditions. Temperatures will be falling into the 40s throughout much of the interior; otherwise, lows in the low 50s can be expected. Temperatures should rebound beautifully during the day, however, as a ridge axis builds in from the west, with high temperatures in the upper 70s. The airmass will remain dry — with dewpoints in the low 40s, relative humidity values may fall below 20%. Definitely a 10/10 day. Another cool night can be expected on Sunday night, but not as chilly as Saturday night.

Monday: The ridge will gradually be moving eastward and will be overhead throughout the day. This will keep our mid and upper level temperatures warm, which helps to keep any lift for showers and thunderstorms limited. Thus, another sunny day should be expected, with temperatures hitting the low 80s. It will be more humid than the weekend, but nothing too uncomfortable, as dewpoints will be in the mid 50s. Overnight lows will be a bit warmer — probably around 60 — as the humidity will prevent ideal radiational cooling conditions.

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Today’s NAM model at 500mb valid for Tuesday afternoon shows a trough moving into the Great Lakes, and while we are still under the influence of a ridge, it will be weakening. This could cause showers and thunderstorms on Tuesday (weather.cod.edu).

Tuesday: The ridging will begin to lose its grip over the area, as a trough approaches from the west and northwest. The weakening of a ridge in the midst of a warm and increasingly humid airmass is often the precursor to thunderstorm development. As the cooler airmass with the trough and our warm airmass with the ridge collide, a warm frontal boundary will form, and may begin to stall due to a blocking pattern to our north and east. The exact location of this boundary will determine how warm our temperatures are, as well as how strong any potential thunderstorms are. Most likely, the boundary will remain just to our north, helping our temperatures stay in the upper 70s to low 80s, with humid conditions, as well as potentially placing us in the foci for thunderstorm development. This will further be augmented by a cold frontal boundary to our west, which would place us in the warm sector (warm sides of both the cold front and warm front). The impressively high moisture values in the atmosphere as well as the slow movement of the boundary make heavy downpours with flash flooding a threat for Tuesday. However, there may also be enough instability and wind shear for some strong wind gusts and small hail as well.

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Today’s GFS model valid for Tuesday afternoon shows incredible high precipitable water values — this means that if the atmosphere were to be “squeezed out” like a wet towel, it would produce over 2″ of water. This indicates a very moist atmosphere — one that is conducive for heavy rain.

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Today’s GFS model valid for Tuesday afternoon shows high surface-based CAPE (Convective Available Potential Energy), which essentially measures how much energy and instability the atmosphere has to produce thunderstorms. Any value over 1,500 J/KG can lead to severe thunderstorms (weather.cod.edu).

Wednesday and Thursday: The exact timing of the cold front from the west passing us will determine if we get more thunderstorms on Wednesday, or a more mundane weather day. Regardless, when the cold front does pass, it will stall just to our south, which may keep some clouds and showers around. The airmass will not be all that cool behind the front, as temperatures may still hit the upper 70s, but dewpoints will be lower, resulting in a drier airmass, particularly throughout the entire atmosphere. This should preclude any severe weather for Thursday, and assuming it passes earlier in the day on Wednesday, severe weather would also be precluded — but if the cold front holds off until the afternoon, more thunderstorms are possible.

 

 

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