Another complex storm system possible next week

On the heels of a large, complex storm system which impacted a large portion of the United States over the past several days, forecast models have continued to hint at the development of another system in 5 to 7 days time. Instead of being just long range model fodder, the hemispheric pattern progression suggests that this storm threat has some legitimacy, with the potential for a moderate to high precipitation event across the Eastern United States once again during the middle part of next week.

Much of the storm threat stems from the development of a cut-off low, or a trough and low pressure system cut-off from the jet stream, in the Southwestern United States later this week and weekend. This cut-off low looks likely to meander in that area for a period of time before ejecting east/northeastwards. The orientation of the upper level jet stream and height pattern suggests that the storm will eject from the Texarkana area towards the Mississippi and Ohio River Valley’s by the early and middle part of next week.

GFS model showing the cut-off low ejecting northeastward into the Mississippi Valley next week.

GFS model showing the cut-off low ejecting northeastward into the Mississippi Valley next week.

The main issue among forecast models is pinning down exactly when the disturbance will eject northeast, and how strong it will be. Some models keep the disturbance meandering further southwest for a longer period of time, while others move it northeast fairly quickly. So timing is obviously an issue with the forecast moving forward. However, confidence is increasing in the occurrence of the storm itself.

As the system ejects, it will bring a fairly notable amount of moisture with it. The cut-off low aids in developing a southerly flow ahead of it, which will draw moisture northward from the Gulf of Mexico into the United States. While frontal boundaries and details are yet to be determined, moisture return and a developing low pressure system seem likely to juxtapose and lead to the potential for heavy precipitation.

Analog data of the forecast pattern supports a notable precipitation event across the Eastern US

Analog data of the forecast pattern supports a notable precipitation event across the Eastern US

The event looks likely to bring impacts over a fairly wide area. Widespread precipitation is possible across the Deep South — including the potential for strong thunderstorms — and moisture is expected to surge northward up the East Coast including the Mid Atlantic and New England. Some wintry impacts also appear to be possible on the storms northern fringes, but this appears most likely across the interior portions of New England. There may also be some wintry precipitation on the storms northwest fringes in the Ohio Valley. But the exact track and intensity of the storm being so uncertain makes these details very difficult to discern at this time.

Analog products add confidence to the idea that the storm system will be rather notable, particularly for precipitation and the potential for strong to severe storms in the Deep south as mentioned above. Probabilities for moderate precipitation extend up the East Coast in to New England based on the analog set.

Over the next few days more details should come into focus regarding the exact track, intensity and impacts of the storm system.

Initial analysis of storm potential next week including areas of notable weather hazards.

Initial analysis of storm potential next week including areas of notable weather hazards.

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