January 2020: Unsettled WX Week Ahead

[Cpv17]

If we’re ever going to get any significant cold this winter, this -pna needs to relax.

[Cpv17]

This is one intense line of storms on the NAM for Friday night:

[MontgomeryCoWx]

This is one intense line of storms on the NAM for Friday night:

Wow... vertical with discrete cells out in front.

[MontgomeryCoWx]

If we’re ever going to get any significant cold this winter, this -pna needs to relax.

It’s forecasted to do just that... it actually enters our sweet spot (2 SDs or less in the mid to long term). We’d like for it to stay negative to neutral in the long term.

[harp]

The GFS has taken away the frozen stuff. Poof!

[Cpv17]

The GFS has taken away the frozen stuff. Poof!

Actually, it has pretty much taken away the cold front altogether. Apparently the front won’t have enough umph to make it this far south as it’s bumping into the SE ridge I’m guessing. Like I said, we need this -PNA to relax to allow the cold air to bleed south towards us. If you look at the CPC, they have us under above normal temps for the next two weeks.

[MontgomeryCoWx]

GFS just pushed it back two to three days which makes more sense given our upper air pattern once we hit late Sunday/Monday. It’s much more of a traditional look for delivering the cold.

With that said, we can get cold with less than ideal patterns, especially when dealing with dense Arctic air that Plummets Montana and the northern plains into the -30s. As Jeff mentioned this morning it’s like water on a table surface. It bleeds south because it’s stronger than what is in its way

[Katdaddy]

A warm and breezy day with some scattered showers will be followed by a severe weather event tomorrow evening through early Saturday morning. We are 1 day out and the enhanced risk area has been expanded to include areas S and SW of Houston. The enhanced risk area also includes all of ETX, portions of NTX including Dallas, and portions of Central TX including Austin. For SE TX any thunderstorms that develop late tomorrow afternoon and evening will need to be watched carefully as they could become supercells however they main threat will be overnight.

From this mornings Houston-Galveston NWS Area Forecast Discussion:

This will be a nocturnal severe weather threat, which will enhance the danger of the event. Not only does this mean that any severe weather that occurs will be harder to see, but also people are more likely to miss severe weather warnings. This is usually because they are either asleep or because they are out and about and may not have their usual means of receiving weather information. If you have plans or events scheduled for Friday night, now is the time to be considering changing those plans. Please make sure that you have a way to receive severe weather warnings (e.g. a NOAA Weather Radio, cell phone alerts, local TV/radio media) and know your plan of action in case a warning is issued for your area.

[srainhoutx]

Thursday morning severe weather briefing from Jeff:

Severe weather threat increasing for Friday night

Severe threats include:

Damaging winds to 70mph
Isolated tornadoes
Isolated large hail

SPC has included much of the area north of I-10 in a 10% probability area of a significant severe weather report (75mph winds or greater or EF2 tornado or greater within 75 miles of a point). The black hatched area in the second graphic below.

Discussion:
A powerful storm system will move into TX on Friday resulted in a highly active weather period Friday night over SE TX. Moisture is rapidly increasing this morning from the Gulf of Mexico as SE winds increase. As the strong upper level trough digs into TX on Friday, strong forcing aloft will promote surface low pressure formation over N TX/OK. The result will be a significant increase in southerly 850mb winds and the formation of a robust low level jet over the region which will transport deep/rich tropical moisture northward across the building warm sector early Friday. 850mb (5000ft) winds will be howling from the south at over 50kts over much of the region with surface winds Friday afternoon averaging 25-35mph. Warm sector air mass will be capped much of the day on Friday as SW winds in the 700mb level help to bring slightly warmer air from NE MX over the region…this will keep a “lid” on things until the later afternoon and evening hours.

By mid to late afternoon as surface temperatures warm into the 70’s the cap begins to erode over the area. Additionally, strong lift will be approaching from the west along an advancing cold front. A squall line of severe storms will develop near I-35 in central TX by mid afternoon and begin to sweep eastward. Ahead of this line the late afternoon warm sector over SE TX becomes unstable with steep lapse rates aloft and surface based CAPE of 1000-2000J/kg (instability). Very strong low level shear will be in place Friday afternoon and evening over the area…the main question continues to be…can the weakening cap erode over the warm sector allowing discrete cells to develop. Given the shear in place Friday afternoon and evening…supercells with tornado potential would be likely if warm sector convection can form. Think the best chance of any discrete cells forming will be mainly N of HWY 105 where the cap is weaker and most likely over Walker, San Jacinto, Polk, and Trinity Counties. If this potential looks more likely early Friday some portions of SE TX could be upgraded to a moderate severe risk level (4 out of 5).

Friday night:
Central TX squall line will advance rapidly eastward across much of SE TX between 700pm and 200am. Damaging winds and isolated tornadoes will be possible with this line. Overall setup is favorable for the strong low level jet above the surface to be brought down to the surface in the form of damaging wind gusts within the line of storms. Echo wave patterns along the advancing line and notches within the line may produce brief tornadoes along the leading edge. A few wind gust to 75mph or greater will be possible with any significant bowing segments of the line which would produce larger corridors of wind damage.

The overall storm system is fast moving and the steering flow is also rapid which is going to result in storm motions of 40-55mph at times. This will greatly limit warning lead times…so actions need to be quick if a warning is issued for your area. Additionally, the majority of the event will take place after dark and in the more populated areas of SE TX likely between 1000pm-100am when people are sleeping. It is vitally important to have a way to receive warnings…the most audible way is your cell phone, but make sure the alerting functions are enabled and on.

Remember tornado and high wind safety precautions…lowest floor, away from windows, interior rooms.

Be aware of the weather Friday night and be ready to act and take action!

Severe Weather Outlook (Friday):

[MontgomeryCoWx]

Going to be an interesting Friday night. I much prefer to see my Severe Weather than get it late at night.

In the mid to long range, our indices continue to move into a favorable spot to deliver consistent cold and Winter opportunities.

[Kingwood36]

GEFS Members starting to get awfully noisy for frozen precip next Friday Jan. 17th into the following week across parts of Tex

[don]

Yeah i wouldnt be surprised if the winter storm showed back up in the models. As the operational GFS still shows a ice storm next week but has pushed it up north into Oklahoma and Arkansas. I wouldnt be surpised if the convegence zone shifted back south into Texas as weve sometimes seen in the past with these setups. I also think something looks fishy on the way the models are handling the shallow cold airmass as some of the models show a 1045mb+ High coming down the plains and then getting shunted to the east without even a freeze in southeast Texas if you believe the 12z GFS. I find that hard to belive with such a strong high comming down the plains and our source region being so cold. Just something to watch over the next week.

[Cpv17]

Yeah i wouldnt be surprised if the winter storm showed back up in the models. As the operational GFS still shows a ice storm next week but has pushed it up north into Oklahoma and Arkansas. I wouldnt be surpised if the convegence zone shifted back south into Texas as weve sometimes seen in the past with these setups. I also think something looks fishy on the way the models are handling the shallow cold airmass as some of the models show a 1045mb+ High coming down the plains and then getting shunted to the east without even a freeze in southeast Texas if you believe the 12z GFS. I find that hard to belive with such a strong high comming down the plains and our source region being so cold. Just something to watch over the next week.

I’m also wondering the same thing. Doesn’t make sense to me.

[harp]

Yeah i wouldnt be surprised if the winter storm showed back up in the models. As the operational GFS still shows a ice storm next week but has pushed it up north into Oklahoma and Arkansas. I wouldnt be surpised if the convegence zone shifted back south into Texas as weve sometimes seen in the past with these setups. I also think something looks fishy on the way the models are handling the shallow cold airmass as some of the models show a 1045mb+ High coming down the plains and then getting shunted to the east without even a freeze in southeast Texas if you believe the 12z GFS. I find that hard to belive with such a strong high comming down the plains and our source region being so cold. Just something to watch over the next week.

I’m also wondering the same thing. Doesn’t make sense to me.

How strong is that SE ridge? Isn't that a key player here?

[don]

That can vey well be the case,having said that models sometimes underestimate the ability for dence shallow air to over power the effects of the ridge. As we've seen many times throughout the years.

[kyzsl51]

If I remember correctly the models backed off and on for most recent winter events?

[Cromagnum]

Main line looks to be in central texas by mid morning. I dont like that discrete look ahead of it.

https://ibb.co/K0MCG87

[MontgomeryCoWx]

If I remember correctly the models backed off and on for most recent winter events?

Every winter event in recent memory has jumped on and off the models. The only one that really took me by surprise was the December snow in 2017, when it popped up on the HRRR the day of, then dumped 5.5 inches in CS and an inch in Magnolia.

[Cpv17]

Main line looks to be in central texas by mid morning. I dont like that discrete look ahead of it.

https://ibb.co/K0MCG87

If we can remain rain free with some peaks of sun throughout the day then watch out!! To me that’ll be key.

[Cpv17]

Yeah i wouldnt be surprised if the winter storm showed back up in the models. As the operational GFS still shows a ice storm next week but has pushed it up north into Oklahoma and Arkansas. I wouldnt be surpised if the convegence zone shifted back south into Texas as weve sometimes seen in the past with these setups. I also think something looks fishy on the way the models are handling the shallow cold airmass as some of the models show a 1045mb+ High coming down the plains and then getting shunted to the east without even a freeze in southeast Texas if you believe the 12z GFS. I find that hard to belive with such a strong high comming down the plains and our source region being so cold. Just something to watch over the next week.

I’m also wondering the same thing. Doesn’t make sense to me.

How strong is that SE ridge? Isn't that a key player here?

Actually the CPC is thinking that the cold could work it’s way down to Louisiana, but not so much Texas.