Severe Thunderstorm Threat for the Gulf Coast

The second day of the new year will feature the threat for severe thunderstorms with the main threat being high wind gusts (up to 30% threat) due to a 50 knots (60 mph) 700 mb jet, though there will be a 5% threat for tornadoes and 15% threat for large hail.  Since this update is occurring around 0600 EST, please refer to the following for further updates:


NWS Lake Charles, NWS Slidell, NWS Houston, NWS Mobile, NWS Jackson

Day 1 Convective Outlook issued at 0604 UTC 01/02/17
Day 1 Tornado Outlook issued at 0604 UTC on 01/02/17
Day 1 Wind Outlook issued at 0604 UTC on 01/02/17
Day 1 Hail Outlook issued at 0604 UTC on 01/02/17

The latest High Resolution Rapid Refresh (HRRR) model (images courtesy of Weatherbell) shows parameters that look conducive for the development of strong to possibly severe thunderstorms by midday across much of eastern TX, LA, MS, and later into AL and the panhandle of FL.  Note the values of surface-based CAPE approaching 2500-3000, especially into central-southeastern LA.  Those values would be good in spring and summer!  Therefore, the air mass is more than sufficient to support thunderstorms.

HRRR 8-hr forecast for surface-based Convective Available Potential Energy (CAPE – buoyancy) valid around 1200 EST or 1100 CST on 01/02/17

Looking at the HRRR forecast for Significant Tornado Parameter, one would look for values above 1 to assess the chance for tornadoes.  With values approaching 3+, this model would suggest the risk for significant tornadoes (EF2+) as the day matures, but note that this is one model run and we will have to see how the air mass adjusts after early morning storms.  Dewpoints of 68+F and veering winds with height would surely lend itself to rotating updrafts, but as the Storm Prediction Center (SPC) states in their overnight update, the main threat at this time appears to be wind gusts of 55+ mph in the strongest storms.

HRRR 8-hr forecast for the Significant Tornado Parameter valid at 1200 EST or 1100 CST on 01/02/17

One final threat to discuss is more heavy rain for much of the Gulf Coast today into tonight before this shifts northeast and up the East Coast into Tuesday.  As you can see from the HRRR radar reflectivity below, plenty of thunderstorms are possible and some training of cells may occur locally.  The WPC Day 1 QPF shows rainfall greater than 1″ for eastern TX into western LA tapering off a bit east, then another area of greater than 1.5″ to as much as 3″ from southeastern LA east to the FL panhandle and southern AL/GA.

HRRR 9-hr forecast Radar Reflectivity valid at 1300 EST or 1200 CST on 01/02/17
The Weather Prediction Center (WPC) 24-hr Day 1 Quantitative Precipitation Forecast (QPF) issued at 0832 UTC on 01/02/17

Mid-Atlantic Rain

Overnight, this current wave of precipitation has over-achieved slightly with 0.16″ recorded so far at BWI.  Expect occasional rain to continue through Tuesday with temperatures in the 40s to around 50.  Much colder weather is on the way later in the week.

Update on the potential East Coast winter storm

The jury is largely still out on this threat, but the 0000 UTC Euro is showing some light, non-issue snow late week, while the 0000 UTC GFS shows a significant snow event possible for the Mid-Atlantic next weekend (01/07-01/08).  More on this later.

Thanks for reading!

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