Good day, everyone!
Before we get into the main topic of this forecast, I'd like to talk about all of this heat. The heat dome that has been dominating much of the eastern two-thirds of the United States remains firmly in place.
The heat is expected to continue across much of the central and eastern United States this week. Across portions of the Central and Midwestern states, temperatures have been reaching the upper 90s to lower 100s. If you're going to be outside for extended periods of time or doing strenuous work, make sure to take breaks and drink plenty of water.
In Dallas, Texas, you can expect several more days with temperatures either right around or just above 100 degrees. Unfortunately, the lack of rain across this region of the country will only further contribute to the building heat.
Oklahoma City will see a similar story, with highs generally ranging from around 100 to 105 degrees over the next several days.
Tulsa will also remain firmly in the heat, with temperatures likely reaching around 100 degrees on multiple days.
Topeka, Kansas, can expect daily highs averaging around 100 degrees, while Salina could see temperatures ranging from around 100 to 107 degrees over the next several days.
Springfield, Missouri, should generally see highs between 98 and 102 degrees.
St. Louis will see a somewhat wider range, with temperatures likely ranging from the mid-90s to the lower 100s. A reasonable high-end forecast would be around 103 degrees.
And these locations are far from alone. Much of the central and southern Plains, along with portions of the southern Midwest, will likely experience similarly extreme heat.
Shifting east into the Tennessee Valley and Southeast, temperatures will remain extremely high as well. Places such as Petersburg, Virginia, and Murfreesboro, North Carolina, could reach at least 100 degrees by Thursday this week.
However, there is a potential pattern shift coming for the eastern U.S. by early next week. This should lead to some relief from these extreme temperatures, while the central U.S. continues to bake.
In the near term, small disturbances will likely travel along the northern periphery of the ridge, bringing multiple rounds of severe weather across the Mid-Atlantic and Northeast. This sets the stage for the severe-weather threat that we'll be looking at next.
Severe Weather
Before we get to the severe weather threat in the Mid-Atlantic, I think it is important to first touch on the severe weather that is ongoing across North Dakota.
Today, the SPC has highlighted a Slight Risk of severe weather for parts of central North Dakota, north-central South Dakota.
Currently, a shortwave trough is situated near the borders of Saskatchewan, Alberta, and Montana. 500 mb winds at the base of the trough are between 50–60 knots, while the surface environment has a decent amount of instability, with around 2,000 J/kg of CAPE.
A strong squall line is currently moving across the Dakotas, where it is producing 60-75 mph wind gusts. As diurnal heating has already begun to wane, these storms are expected to weaken over the next couple of hours.
On Monday, the severe weather threat becomes considerably more scattered compared to today. A deep upper-level low will continue moving eastward across southern Saskatchewan and Manitoba, with 40–50 knot winds at midlevels spreading across the Northern Plains and Upper Mississippi Valley.
The greatest instability will be farther south, where a weak surface trough extending from Wisconsin through Iowa and Nebraska will provide a potential focus for thunderstorms. cape values could reach 2,000–3,000 J/kg across Iowa, Wisconsin, and northern Illinois. However, forcing will remain fairly weak, which should keep thunderstorm coverage limited.
A few isolated storms could develop across Wisconsin during the afternoon, with hail over one inch possible. Additional isolated thunderstorms may develop from Iowa into northern Illinois overnight.
Farther west, a better chance for thunderstorms will exist from Colorado into Nebraska as another upper-level disturbance moves northeastward. Strong diurnal heating across the Central High Plains should allow storms to develop near the Front Range before spreading northeastward into Nebraska. Some storms could produce strong to severe outflow winds, with marginally severe hail also possible.
As we push into Tuesday, our attention begins to turn toward the Northeast. A zone of moderate instability is expected to stretch from the Upper Midwest eastward into New York, Pennsylvania, and New Jersey, along a weak surface trough where scattered thunderstorms will be possible.
A disturbance moving across the Great Lakes and into the Northeast will bring 30–40 knot northwesterly winds at midlevels, providing additional lift and potentially cooling the atmosphere aloft enough to help destabilize the region.
The greatest concentration of thunderstorms is expected from New York into Pennsylvania, both during the day and overnight. Some storms could develop early from southern New England into New York, where elevated instability will already be present. As the atmosphere destabilizes farther south, additional storms could develop along outflow boundaries or a developing afternoon surface trough.
While large-scale forcing will remain relatively weak, localized areas of convergence could be enough to initiate additional thunderstorms. The environment may favor more cellular storms, with hail and locally damaging wind gusts being the primary threats.
The threat could continue into Tuesday night as the disturbance moves eastward. Several models suggest thunderstorms moving out of Ontario overnight, with some potential for strong winds as they move into the Northeast.
Farther west, thunderstorms will also remain possible from Nebraska into northwest Iowa. Strong daytime heating combined with moderate instability and a developing southerly low-level jet could support new storm development, with perhaps a few supercells capable of producing hail. Storm coverage could increase during the evening before spreading northeastward.
As we move into the middle of the week, we see that the atmosphere still is not ready to give up. Multiple disturbances will move across the top of the ridge from the Great Lakes toward the East Coast.
This pattern could lead to several consecutive days of severe thunderstorms across portions of the Northeast and Mid-Atlantic.
For Wednesday the Storm Prediction Center has already outlined a 15% risk over portions of the Mid-Atlantic, and including most of the state of Pennsylvania. A shortwave trough is expected to move across the lower Hudson Valley and into the Mid-Atlantic, with enough instability and wind shear in place to support organized thunderstorms.
Wednesday's storm activity will depend heavily on where Tuesday's thunderstorms leave behind cooler, more stable air. Those leftover areas could influence where storms develop and shift the location of the greatest severe-weather threat. Because of that, the location of the risk area could change considerably in future forecasts.
By Thursday, another disturbance is expected to move along the northeastern edge of the ridge and across the Mid-Atlantic. With sufficient instability and wind shear likely remaining in place, another round of severe thunderstorms will be possible.
The Storm Prediction Center has introduced a 15% severe-weather probability for across much of the same areas as Wednesday. As with Wednesday, however, the exact location of the threat will depend heavily on how the atmosphere is modified by storms that have occured over the past couple of days.
Friday could bring yet another round of severe weather as a stronger mid-level disturbance moves into the Mid-Atlantic. Adequate instability and deep-layer wind shear could support at least an isolated severe-weather threat.
Exactly where the greatest threat will be remains highly uncertain. With thunderstorms occurring repeatedly from Tuesday onward, each round of storms will modify the environment and shift the boundaries that later storms develop along. This makes it very difficult to pinpoint a specific corridor of severe weather this far out.
For now, the Delmarva Peninsula appears to be one of the areas that could see more organized storm activity, but that will likely change as we get closer to the event.
Flooding Threat Increases
An increasingly active monsoon pattern will bring a growing risk of excessive rainfall to the Southwest and Four Corners through Monday. Moisture will surge northward from Baja California, supporting widespread thunderstorms and locally intense rainfall across the region.
For today, the SPC has highlighted a Slight Risk of excessive rainfall across portions of the Southwest and Four Corners.
An unusually strong flow of moisture is moving northward from Baja California into the Southwest and Rockies. Precipitable water values are expected to rise above one inch as far north as the Four Corners, while enough instability will be present to support widespread thunderstorms across Arizona, New Mexico, Utah, and Colorado.
With 30–40 knots of wind shear, storms should be capable of organizing into clusters. Rainfall rates could exceed one inch per hour, and training storms could increase the flooding threat.
The greatest concerns will be across vulnerable terrain, burn scars, areas with saturated soils, and more urban locations. Another round of thunderstorms could develop across Arizona tonight as a stronger disturbance moves northward, potentially producing more widespread heavy rainfall.
The flooding threat becomes more concerning on Monday. The Weather Prediction Center has upgraded portions of Utah to a Moderate Risk of excessive rainfall as another widespread day of thunderstorms is expected across the Southwest and Four Corners.
The region will remain trapped between an approaching trough to the west and the strong ridge to the east. Multiple disturbances will move northward through this flow, providing additional lift to support even more storms in an atmosphere already containing an anomalously high amount of moisture.
Precipitable water values are expected to remain above one inch across Utah, Arizona, and western Colorado, with some areas seeing values around two standard deviations above normal. Once the atmosphere destabilizes, storms will likely become widespread, with some capable of producing rainfall rates exceeding one inch per hour.
The storms may not move particularly slowly overall, but the potential for training thunderstorms moving over the same areas will increase the flooding threat. This is especially concerning given that portions of the region have already received heavy rainfall over the weekend.
Farther east, heavy rain will also be possible along a frontal boundary stretching from the Upper Midwest through the Great Lakes and into the Northeast. Scattered thunderstorms could produce rainfall rates of 1–2 inches per hour, with some potential for storms to train along the boundary.
Meanwhile, the Gulf Coast remains an area to watch. A mid-level low that has been lingering over the northern Gulf is beginning to organize, with tropical moisture becoming increasingly concentrated across the region. Precipitable water values of 2–2.25 inches will support slow-moving thunderstorms along the Gulf Coast through Monday.
For now, the heaviest rainfall is expected to remain mostly offshore, however, he National Hurricane Center is monitoring the low, designated AL97, and gradual development is expected as it moves slowly west-northwestward toward the Upper Texas and southwestern Louisiana coasts.
The Tropics
An area of low pressure, currently designated AL97, is located about 125 miles south of southeastern Louisiana and continues to become better defined, with shower and thunderstorm activity gradually increasing. Conditions are expected to remain favorable for further development, and a short-lived tropical depression or potentially Tropical Storm Edouard could form before the system reaches the Upper Texas or southwestern Louisiana coasts on Tuesday or Tuesday night. The National Hurricane Center has currently given this system a 70% chance of becoming at least a tropical depression over the next two days.
Interests along the southwestern Louisiana and Upper Texas coasts should closely monitor this system, as tropical storm watches or warnings could become necessary later tonight or Monday morning. An Air Force Reserve reconnaissance aircraft is also scheduled to investigate the system Monday morning, which should provide a much better understanding of its structure and potential for further development.
Regardless of whether the system reaches tropical-storm strength, locally heavy rainfall is expected along portions of the Upper Texas and southwestern Louisiana coasts over the next several days, with an increasing flood threat as additional rounds of rain affect the region. The Weather Prediction Center has already highlighted a marginal risk of excessive rainfall for the area over the next several days. I will continue to monitor this situation closely and provide updates as we needed.
Meanwhile, the remnants of Tropical Storm Dolly are producing showers and thunderstorms from Puerto Rico eastward across the Virgin Islands and northern Leeward Islands. Satellite data and surface observations show no signs of a closed circulation, and redevelopment is unlikely over the next day or two as the system moves westward to west-northwestward at around 25 mph.
Even without redevelopment, locally heavy rainfall and gusty winds will be possible across portions of the Leeward Islands, Virgin Islands, Puerto Rico, and Hispaniola over the next couple of days.
As we reach the middle part of next week, conditions could become more favorable for redevelopment as the wave reaches the southeastern Gulf of America, so this system will be worth watching as it continues westward.
The National Hurricane Center currently gives the system a near 0% chance of development over the next couple of days and a 20% chance over the next week.
Nice Temperatures Across the North
To end on a bright note, temperatures across the northern tier of the United States are once again looking quite comfortable
The north-central U.S. may remain a little toasty; however, the Pacific Northwest and most of the Northeast should remain rather pleasant. Make sure to get outside and enjoy the nice weather when you can.
Thanks for reading, and we'll see you next time!