Summer weather to prelude the upcoming Memorial Day weekend!
5/24/10 -Pleasant, summer weather the last two days is predicted to continue through the week and into the Memorial Day weekend. A rapid pattern change occurred over the United States at the end of last week. The eastern US went from being in a dynamic, active pattern into a much quieter, summer pattern that one would expect in late July. The summer pattern includes a upper level, 300mb ridge in the eastern US that keeps the region in a much calmer pattern. This can be seen below with the peak at the end of the black arrow.
This allows warm southerly air to push northward and remain in place. The trough in the Western Plains/West Coast, takes all the storm systems into Canada and to the north of Ohio. The path the systems follow is indicated by the red line on the above image. The stagnant pattern under the ridge is allowing a weak low pressure system off the Atlantic coast to remain nearly stationary. This is allowing clouds to stream westward the next several days over the southeast Ohio region. The clouds origin and movement westward is indicated by the green arrow revolving around the low over the Atlantic (represented by a red L).
These on and off clouds that will continue the next few days. These are providing a stable layer in the atmosphere that prevent the development of summer pulse storms (storms that build quickly and die just as quickly, often not moving much in its short life-span). This mode of storms are typical with this type of pattern in the warm sector of a ridge. The discussed clouds can be seen on the latest visible satellite streaming in from the east around the low. Pulse storms that we would see without that low are evident in other parts of the US are shown within the light blue circles. Another storm system in the upper Plains/Canada and its associated cold front that is nearly stalled are labeled by the purple L and the blue line.
This pattern will not change until Friday when some synoptic dynamics will alter the current pattern slightly across the US. The ridge will weaken over the eastern US and actually retrograde (move against the westerlies, westward) into the eastern Plains. This will allow a trough to try to establish itself over the eastern US on Friday. The developing trough is indicated by the brown arrow and the retrograding ridge’s movement is shown by the black arrow on the 300mb chart.
This will allow weak northerly winds on Friday and provide the opportunity for some showers and thunderstorms for the first time in nearly a week. These will be focused along a very weak cold front/trough that will pass through the area during the day. The coinciding, northerly wind shift can be seen at the 850mb level over the Ohio region. This will bring a slightly lower temperature for Friday and Saturday, but near 80 is still expected.
The good news is that this 300mb trough will not deepen much and will give way to ridging once again in the east Saturday. This will allow the redevelopment of high pressure to build in to the region for the weekend. The following is an animation of the 8am predictions of the GFS model for Friday through Tuesday. The red line is the weak trough that will build in bringing a chance of showers Friday and into early Saturday. The yellow line is the ridge that retrogressed westward Thursday through, Friday and will progress eastward during the weekend. The dashed line represents the cut off portion of the jet that will abandon the renegade trough, cutting it off over time.
With the ridge building back into the region on Saturday, the above normal temperatures will remain along with sunny skies. The only exception that warrents watching is the lack of a low off the east coast during this timeframe. The pattern will be much like that of this week, only no stable layer will exist allowing for the development of pulse storms as mentioned earlier. This could increase the chances of sporadic showers and thunderstorms late in the weekend. This forecast period is so far out however, that any mesoscale features that could develop or exist might provide the weak cloud cover/stable layer to prevent the developement of this precipitation. Once again, its so far out it is very difficult to predict this development.
The last slide has a large black arrow across the US. This represents the nearly zonal flow that will exist beginning mid-week next week. This is usually representative of near normal temperatures and not a very active pattern with little precipitation expected. MORE NICE WEATHER!
Make sure you get out and enjoy the fabulous weather the next week and have a great Memorial Day weekend! The good weather isn't going to last forever!
Christopher Redmond
cr898005@ohio.edu
