Severe Weather Possible Wednesday

Convective outlook for Wednesday (Day 2). Image source: SPC

Convective outlook for Wednesday (Day 2). Image source: SPC

The strong cold front that has pushed through the central CONUS over the past two days will begin to approach the region from the west on Wednesday. This slow moving front has already produced severe weather to our west and looks to potentially still have some kick to it Wednesday afternoon/evening.

The cold front in question is associated with a strong deep upper-level trough digging pretty far south for this time of year. With warm, humid air still lingering from summer, an air mass clash like this produces some severe weather similar to what we see during the spring. To our good fortune this through is becoming more negatively tilted with the front already starting to occlude over IL, IN, MI. Even still, the front will bring the threat of severe weather to our area but not to the extent that it has brought our neighbors to the west.

This will be a slow moving front so we will be dealing with the effects all day Wednesday. Winds have already picked up ahead of the front which helped usher in some warm and humid air into the region this afternoon and will linger into the night. Some light showers with isolated pockets of heavy rain have over far inland sections and should continue through the night. No lightning has been detected with the activity over land though some lightning activity has been detected over the Atlantic Ocean.

Wednesday will be the active day as the cold front will continue to push it’s way to the east. A south-southeasterly flow will develop at the surface Wednesday morning and some lingering showers will still pop up but should remain brief and isolated. By early afternoon, higher temperatures and dewpoints, as well as greater instability, will be present to allow strong to severe cellular thunderstorms to develop well ahead of the front. These storms will move very quickly and have the potential to produce very heavy rain and an isolated tornado can’t be ruled out given some weak wind veering with height on the forecast soundings. This is where I believe the greatest threat of severe storms will occur. Timing will also be important to the location of severe storms. By the afternoon when heating becomes stronger, the axis of greatest instability lines up from highway 17 and locations eastward.

HRRR model shows the front pushing through the Charlotte area early Wednesday morning with some scattered convection over ENC.

HRRR model shows the front pushing through the Charlotte area early Wednesday morning with some scattered convection over ENC.

CAPE values well ahead of the front are supportive of severe convection.

CAPE values well ahead of the front are supportive of severe convection.

Lifted index forecast for Wednesday afternoon highlighting the area of greatest potential for upward motion (increased convection). The highest values occur east of highway 17 where the greatest threat of severe weather exist.

Lifted index forecast for Wednesday afternoon highlighting the area of greatest potential for upward motion (increased convection). The highest values occur east of highway 17 where the greatest threat of severe weather exist.

While the eastern half of ENC will have greater instability early on, the western half will still have to battle the frontal passage as a line of heavy showers and storms will be on the lead side of the front with the main threats of strong winds and dangerous lightning.

Forecast soundings also indicating precipital water values around 1.75″ – 2.00″ when combined with the slow motion of the front will give greater attention to higher rainfall totals as a result of the frontal passage. Right now most areas could see about 1″ of rain while areas under heaver showers and storms could see rainfall totals nearing 2-3″.

While I won’t be able to provide regular updates during the morning and early afternoon, my twitter feed will pass along any watches, warnings, or advisories that the NWS might issue. To receive these tweets, follow @encweater on twitter.

A brief update on the tropics: Hurricane Gonzalo has become a category 3 hurricane just north of Puerto Rico on Wednesday. Further strengthening can be expected over the next several hours and it continues making it’s way to the northwest. As previously pointed out in a previous update and confirmed by high confidence in forecast model tracks, the upper-level trough producing Wednesday’s severe weather will serve to turn Gonzalo more northward and eventually northeastward away from the US coast. Unfortunately this forecast doesn’t spare Bermuda from another strong tropical cyclone. Fay was a glancing blow but Gonzalo looks to be on a more direct path and forecast to be stronger than Fay. I will continue to monitor but high confidence in no landfall in the US.

Visible satellite image of Hurricane Gonzalo before sunset on Wednesday evening.

Visible satellite image of Hurricane Gonzalo before sunset on Wednesday evening.

Forecast track for Hurricane Gonzalo.

Forecast track for Hurricane Gonzalo.

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