This has been our pattern for a couple weeks, because the jet stream at 30,000 feet is racing across the U.S. in a largely west-to-east configuration. When the jet stream flow in straight configuration, without significant meanders or bends, storm systems at the surface remain weak and fast-moving.
There are a few elements expected to come together Thursday morning, bringing the threat of a light wintry mix. These are shown in the forecast map below:
|Surface forecast chart, Wednesday evening.|
The source of moisture aloft is the second element shown above - a developing coastal low pressure system over the southeast U.S. The system will slide toward the northeast on Thursday morning, to a location off Cape Hatteras.
Now, let's advance the forecast map by 12 hours:
|Surface forecast chart, Thursday morning.|