Powerful Front Coming Later This Week ... Any Chance Of Severe Weather?
With a warm, humid airmass in place, I am sure many of you are wondering if the powerful front later this week could produce any severe weather. In this blog, I am going to break down the severe weather threat late Friday / Saturday.
Storm Prediction Center Severe Weather Risk Friday / Saturday
SPC is not placing any of our area under a slight risk of severe weather either Friday or Saturday. This doesn't mean it cannot happen, this just means they are not confident enough in the data to place us in a slight or they just think it is not possible.
SPC has eluded to the fact that they feel a slight could be warranted at some point, but due to some inconsistencies in the data they will hold off for now. Here is their wording...
"SOME SEVERE POTENTIAL WILL LIKELY ACCOMPANY THE DIGGING TROUGH AND ASSOCIATED/SEWD-MOVING COLD FRONT AS THEY MOVE ACROSS THE CENTRAL U.S. DAY 4. WITH AMPLY UNSTABLE WARM SECTOR AND MODERATE WNWLYS AT MID LEVELS...THE ENVIRONMENT SHOULD BE SUPPORTIVE FOR AT LEAST ISOLATED STRONGER/SEVERE STORMS. HOWEVER...COVERAGE/INTENSITY ANTICIPATED DOES NOT ATTM WARRANT INTRODUCTION OF A THREAT AREA."
Severe Weather Discussion
This strong cold front will be aproaching the area on Friday and push cold air into our area all day on Saturday. This means we may have some timing issues with the best forcing for storms and the best wind energy/instability. Let's look at the data and keep in mind the severe weather ingredients I look for when forecasting organized severe weather events.
This front looks a ton like the last two strong cold fronts that moved through in August. Both had some issues with the timing of the most favorable parameters for severe weather. This storm system has the best forcing moving across the area Saturday which is basically behind the cold front.
GFS Mid Level Disturbances Late Friday
Notice the core of the disturbance is just west of the Great Lakes area of the US late Friday.
GFS Mid Level Disturbances Late Saturday
Notice the core of the disturbance is moving directly across our area late Saturday. The problem is this is after the front has already moved through.
By the time the upper level forcing gets here on Saturday, the front is well south of our area and temperatures have dropped off significantly.
It becomes clear that if severe weather is to fire, it would need to do so Friday because Saturday is well behind the front.
There is no question that Friday will have some instability, but how much is somewhat questionable. We will have incredibly humid air in place on Friday with very warm temperatures, but the upper level low is so far west that it will mitigate some of the warm air's ability to produce instability. Unstable air is a combination of hot and humid at the surface along with cold air aloft. Since there will be nearly no cold air aloft, this lowers instability somewhat late Friday.
GFS Instability Late Friday
Notice the GFS does show 1500 - 2000 units of instability across our area on Friday. To be honest, if there is some wind energy then this will support a severe weather threat.
Wind Energy / Shear
The wind energy on Friday is not very impressive at all, but it may just meet minimum criteria for severe weather. Keep in mind that I look for wind energy of about 35 knots / 40 mph about 6 miles above the ground as the bare minimum to support an organized severe weather threat. The data shows the lower levels of the atmosphere has very weak wind energy, but the mid levels are closer to the criteria I describe above.
GFS Wind Energy 1 Mile Above The Ground Late Friday
Notice winds at this height are a pathetic 5 knots / 5 mph.
Notice winds at this height are bordering on 35 knots / 40 mph. While the lower level wind energy is weak, the mid level flow is borderline acceptable for a slight risk of severe weather.
My Thoughts On Severe Weather Potential Later This Week
The forcing on Friday is not superb but it should be acceptable to fire storms. By Saturday the forcing becomes stronger, but the cold air has already moved in so this means the show would be on Friday if it happened. The instability is sufficient to support severe weather on Friday and the wind energy does look like it will be marginally sufficient to support an organized severe weather threat. The GFS and EURO both show low end, but sufficient wind energy late in the day on Friday. While I have to say the combo of wind energy / instability / forcing is not incredibly impressive, I think it may be enough to support some severe storms with the main threat being hail and damaging winds. The GFS does indeed fire scattered storms late Friday and Friday night.
GFS Precipitation By 8 PM Friday
Notice the scattered storms across our area.
GFS Precipitation By 2 AM Saturday
Notice the GFS still has scattered storms late Friday night and early Saturday morning.
I think it is certainly possible that SPC will introduce a slight risk of severe weather for our region on Friday at some point in the next 48 hours. I think hail and damaging winds look like the primary threat on Friday and I do expect at minimum for SPC to introduce severe weather probabilities for our area soon. I will be watching closely.
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