For most of the nation, it will be a very quiet Thanksgiving week with the majority of the nation receiving little or no significant precipitation. However, there are two areas of interest, the Pacific Northwest and central parts of the nation.
Pacific Northwest (PNW)
The pattern of heavy precipitation over the PNW that started early in November continues this week with at least 2 inches of rain, or up to a foot of snow over higher elevations. Nearly 2 inches of rain fell during a 6-hour period in a Seattle neighborhood. Flooding is expected on a number of rivers in the region. While this pattern of enhanced precipitation is lilkely to continue through the rest of the month, the heaviest period of rain this week has likely ended with more modest rainfall amounts over the next few days.
Rain and Snow Event
A front will pass through the middle of the nation the latter part of this week resulting in light or moderate precipitation. Snow is expected over portions of the Upper Midwest and Great Lakes. Lake-Effect snow will occur from late Friday into Saturday downwind of all of the Great Lakes.
Further south, across Missouri, Arkansas, Oklahoma, and Texas–rainfall will range from very light to moderate in spots. The following image shows the upper structure of this system. The red-dashed line indicates the upper system or trough of low pressure. This system is weak and fast-moving, which will limit the quantity, extent, and duration of rainfall.
The color-shading on the image indicates Precipitable Water (PW)–the total amount of moisture within a vertical column of the atmosphere. Green and yellow regions are higher amounts of PW. Weather models are indicating that a narrow band of atmospheric moisture could be pulled northward just ahead of the system. However, considering the limited amount of time available to transport moisture north, a fast-moving system, and weak upper support– rainfall amounts will be modest at best.
Here is an update on rainfall totals for the rest of the week.
NOAA Winter Update
NOAA updated the forecast for this winter period–DEC-JAN-FEB. It follows. I will discuss this in more detail in my December newsleter.
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