Another busy week of weather is in store for the United States, but thankfully the tropics have returned to relatively quiet levels.
This is your 5 Things to Watch for this week.
Rising Rivers Behind Florence:
Even though the heavy rain is beginning to clear out of the southeastern US, that doesn’t mean the impacts will come to an end. All of the water that came down since late-last week has now made it into the rivers, allowing for many waterways in the Carolinas to reach major flood stage, and in some cases record crests.
This includes the Lumber River at Lumberton, NC. The river gauge actually stopped reporting Sunday afternoon when the water level was at 24 feet, but it is forecast to crest at 25 feet this Monday. That would break the record of 24.39 feet during Hurricane Matthew in 2016.
There are numerous rivers that are currently experiencing flooding or are forecast to overflow their banks later this week as far west as the Appalachian Mountains. As of Monday morning, 58 locations, or river gauges, are in flood stage, 18 of which are experiencing major flood stage and 13 in moderate.
Thankfully, no additional rain is in the forecast this week for the Carolinas and surrounding locations, which will allow for rivers to gradually recede beginning late-week or possibly even as late as this coming weekend. Once this begins, the clean-up process from Hurricane Florence can finally start.
Florence Brings Rain to Northeast:
Florence has slowly moved inland during the weekend over the Carolinas. Now that it has reached the Appalachian Mountains, it has to escape somehow, so it will take a path up the mountains and through the Northeast, bringing heavy rain and thunderstorms to much of the Ohio River Valley, New England, and the Mid-Atlantic between now and Tuesday.
As mentioned, some of this rain will be heavy given the tropical entity moving through. Along the northern periphery of the moisture will be an area of convergence from the northern Mid-Atlantic through central New England, which will enhance rainfall totals. It’s these areas that will likely experience anywhere between 2 and 6 inches while areas to the south pick up generally 1 to 3 inches.
A new round of summer-like heat will move across parts of the central US through midweek associated with a ridge of high pressure traversing the nation. This ridge will promote temperatures upwards of 10 to 25 degrees above-average. On Monday, the warmest of the temperatures relative to average will be found from the central Rocky Mountains through the Midwest, even into northern New England. Actual high temperatures will generally be near 90 degrees.
While cooler air oozes into the upper Midwest and northern New England, the heat will remain intense across the central Plains and lower Midwest, with high temperatures still near that 90 degree mark on both Tuesday and Wednesday. A location or two may even break their daily high temperature record.
By Thursday, the central Plains will cool back down close to normal while the heat peaks in intensity across the Midwest. Temperatures will be as much as 25 degrees above-normal, which translates to highs up to 95 degrees. Cooler but seasonable air will then return in time for the weekend, while the eastern US experiences above-average temperatures, although not at the same magnitude.
Midwest Flood Threat:
A developing area of low pressure over the Plains will track toward the Midwest midweek. This will promote rounds of heavy rain and thunderstorms along a warm front draped across southern Minnesota and central Wisconsin. This warm front will act as train tracks for the precipitation to follow, and since moisture will be streaming in from the south, the persistent round of heavy storms will aid in the risk for flooding in this region between Tuesday and Wednesday night. Up to 5 inches of rain is forecast to fall near the Minnesota-Iowa border with a sharp rainfall gradient.
The model guidance ie beginning to hint at the risk for the first substantial snow of the season for parts of the Northwest, centered around the northern Rocky Mountains. Based on the Monday morning’s runs of the American (GFS) and European (ECMWF) models, there is an area of low pressure over the northern Plains with varying pressure. The ECMWF model has the pressure down to around 985 mb (stronger storm), while the GFS is closer to 1000 mb (weaker storm). There are also differences in timing of the precipitation and the cold air. The ECMWF model has the moisture still in place as the cold, freezing air moves in behind the low, which would allow for snow in the northern Rockies early next week. Then there’s the GFS model, which clears the moisture out before the cold air arrives. Given the uncertainty at this time, snow is possible in the region in about a week from now, but there are a lot more questions than answers that exist at this time.