Historic winter weather and arctic cold event for the Greater Houston Metro (February 14, 2021)

Disclaimer: the views expressed in this post are mine and mine alone and do not represent the views of the company that I work for, IBM, or its subsidiary, The Weather Company. By reading this, you the reader assume full and sole responsibility for the outcome of any action that you take on the content provided herein. You indemnify and hold me, the writer, and my employer, IBM, blameless.

Note: this is simply an informational post meant for linking on social media. I do have planned what I hope will be a far more interesting retrospective on this event in which I’ll attempt to provide historical, meteorological and climatological context for this once-in-a-generation event for these parts.

What may wind up being recorded as the most extreme winter precipitation and thermal event in the modern era appears imminent for a big chunk of the Lonestar State. Not to detract from our neighbors to the north in Oklahoma, who have already been suffering under a truly mind-blowing duration of extreme cold (going on 9 days of sub-20F in parts of the OKC metro area). Preparations should be rushed to completion. Aside from the mandatory steps to protect pipes and pets, this should include plans to deal with *prolonged power outages and water supply disruptions.* See the attached Winter Storm Impact graphic, something I’ve never even thought about consulting for this area before despite following weather in this area for 40 years!

Overview:

There are few substantive changes to the forecast. Expect exceptional winter storm conditions (for our area) to develop overnight with 2-4″ of snow across northern half of the area – possibly more in spots – on top of a layer of ice and sleet. Temperatures will likely remain in the teens all day Monday, bottoming out in the single digits by early Tuesday AM. This combo of non-negligible accumulating multi-modal winter precipitation and durable sub-freezing temperatures makes this an exceptional event for this region.

Precipitation details:

Model-derived soundings from the across area suggest that there remains a warm layer within the lower troposphere about 1.5-2 km deep in this area. As this layer is lifted and cooled by the approaching storm system, a transition through all three major precipitation phases will occur in our region. Cold rain should become widespread across Harris County with some icing on elevated roadways imminent throughout the region. This will transition to freezing rain mixed with sleet by 5-6 pm across northwest and north Harris and Montgomery Counties (which has already experienced some). Roads will very quickly ice over and travel will become increasingly perilous. Precip will most likely transition to a predominant sleet mode sometime in the 9 pm to midnight window (all times should be treated as best guesses). Some snow will likely mix in as well and a heavy sleet/snow mix is likely at some point in the roughly 10 pm through 1 am time frame. Thereafter we should change over to heavy snow and by Monday mid-morning I think that the Magnolia/Tomball/Spring/Klein/Cypress/Aldine/Jersey City/Fairfield area will see anywhere from 2-4 inches of snow with some upside risk. Areas to the north will see as much as 4-6″ with higher pockets. How much snow vs ice vs sleet is entirely dependent on the timing of the transition between phases. The more freezing rain/icing we see before changeover to sleet/snow, the earlier/more widespread/durable power outages will be across the Centerpoint and (to an extent) Entergy districts will be. Skies should quickly clear by mid-late Monday morning, setting the stage for the coldest temperatures of the modern era.

Temperatures:

All-time record lows are in jeopardy. With fresh snow laid down, most of the incoming solar radiation will be reflected while a fresh batch of Arctic air is transported into the area from the north. This means temperatures will likely start out in the teens across the northern part of the Houston metro and low 20s south, falling slowly during the day. By sundown Monday, we will have spent the entire DAY below 20F (since around 1-2 am actually) and won’t crack above until probably around 11-noon Tuesday. If this holds true, this will be WITHOUT PEER in the modern meteorological area. You’re talking the likelihood of spending nearly ONE AND A HALF DAYS BELOW 20F IN HOUSTON. See the attached meteogram (courtesy of WeatherBell) from this morning’s HRRR to see how incredible this looks on a timeline.

By comparison, the great late December 1989 event saw us spend “only” 19 hours below 20F! Temperatures will likely bottom out sub 10F (our area could see anywhere between 4 and 12F) with colder to our north. Sub-zero is possible as close as B/CS and Huntsville. * Mid-week encore?*Hopefully we will warm up enough that the next winter storm will remain north of the Houston metro. Something I’ll dig more into later today before we lose power.

Impacts:

I glossed over in the overview but it’s noteworthy that ERCOT appears not ready to handle the load. Power has been limit up over the weekend and rolling blackouts certainly appear possible – if not probable – by Monday across the area. In addition, any place that gets a heavy initial ice accumulation on overhead lines and/or trees abutting those lines will likely see the power served by said lines disrupted. It’s not clear to me that CenterPoint is going to be able to restore power as quickly as they usually do in the aftermath of the weather modalities that usually knock out power around here (i.e., tropical cyclones and squall lines). Thus, be prepared for prolonged power outages! Charge those cell phones, protect sensitive medications and for goodness sake get pets and homeless folks OFF THE STREETS AND OUT OF THE YARDS. Regardless of efforts made to protect exposed pipes, I do expect that many will suffer very serious damage to their water infra. Plumbers will be quite busy throughout the area.

Summary

While this is normal winter weather for North Dakota, this area never built this kind of event into its plans when designing infrastructure. Thus, expect a very sizable disruption to your daily lives and please have plans to keep people and pets warm and safe. Avoid travel beginning this evening through Tuesday morning. Please, stay safe.

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