Tuesday Night Outlook
Text from the RACES Tuesday Night Net:
High temperatures for the rest of the week will range from the mid- to upper-40’s, with nightly lows in the mid-30’s. Things should cool off on Saturday, leaving the weekend into the beginning of next week with highs in the mid-30’s and nightly lows in the mid-20’s.
Friday night and Saturday we will have a chance of rain, with a changeover to snow on Saturday possible but unlikely. Otherwise, skies will remain partly to mostly cloudy.
Bruce won’t be able to give you the extended outlook on tonight’s net, but you can find it along with a more detailed discussion of this week’s forecast on our blogs on the Lake County SKYWARN website.
Detailed Forecast Discussion:
A semi-split regime in the upper air pattern over the past few weeks has allowed a series of vortices to swing through the southwest states towards the western Gulf of Mexico. The northern branch of the jet stream has kept the Westerlies around 40-45 N and has helped to provide an unseasonably mild period for the Midwest. The current situation reflects this overall pattern with an upper low over extreme northern Mexico south of Arizona moving slowly eastward. With the Westerlies entrenched so far north, this system is likely swing along the Gulf Coast and southeast states Thursday through Friday as it weakens.
A surface high over the Ohio Valley will maintain a slowly increasing southwesterly flow into the region with mild temperatures over the next few days. The atmosphere is essentially isothermal up to 800MB today, and surface temperatuers have been slow to rise, mixing only to about 950MB this afternoon. Model soundings for tomorrow look similar, so I’ve shaved a few degrees off of the guidance temperatures. This may hold true for Thursday as well, depending on whether the low levels winds increase very much.
The southern low will eject out of the southeast states on Friday, with a brushing of precipitation south of the area. The northern branch reflection of this system is expected to swing through the area with a chance of rain, and the possible changeover to snow is looking unlikely at this time. All the models look generally in sync with this scenario, although the ECMWF is somewhat weaker and faster with the southern low.
After that, it appears that a trend towards more “troughiness” over the CONUS may be in store as a broad cyclonic regime sets up across southern Canada into the upper Plains after the weekend. This would initiate a cooler period, although a strong intrusion of Arctic air isn’t evident at the moment. In any event, unseasonably warm and dry conditions should hold through the beginning of next week.
