Tuesday, December 13, 2016 7:47 PM

Several Shots At Wintry Weather (Southern Plains)

Christopher Nunley

There’s a lot to talk about for the Southern Plains over the next week, so I will get straight into it. This discussion will update the Saturday-Sunday snow potential, the storm system I mentioned for early next week in the Southern Plains, and the chance for very light wintry precipitation as early as tonight in some areas.

Tonight:
A reinforcing surge of cool air has moved into Oklahoma today and is moving into Texas this evening. Temperatures with this airmass are in the 20s and 30s in Oklahoma with windchills well below freezing. While winds are from the north at the surface, bringing in this cool airmass, the winds about 1000 feet above our heads will shift towards the southeast overnight. This will force a warmer airmass over the cool airmass at the surface, which should lead to overcast conditions by morning and possibly light drizzle in some areas. This light drizzle, while spotty in nature, may fall into surface temperatures that are at or below freezing in parts of central Oklahoma by early tomorrow morning. Freezing drizzle amounts will be extremely light for Oklahoma and no travel issues are expected (remain alert on bridges and overpasses in case a slick spot were to develop). Luckily, much of the spotty drizzle appears to stay just east of the 32-degree line. Conditions should improve by late morning.
slide02
3km NAM Composite Reflectivity: Wednesday Morning

Wednesday Night and Thursday Morning:
Another round of very light freezing drizzle is possible overnight Wednesday. The precipitation will remain light, however, it is expected to be more widespread than tonight’s drizzle. This could lead to a few slick spots for the Red River Counties of north Texas, much of western Texas, and Oklahoma. I want to reiterate amounts will be very light and likely less than .01”, but we all know it doesn’t take much ice to cause travel issues on elevated surfaces. There could be a snowflake or two in parts of Oklahoma, but analyzing the entire atmospheric column at this points, doesn’t show a promising snow profile. Conditions should improve by late in the morning on Thursday.
slide03
3km NAM Composite Reflectivity: Thursday Morning
slide04
3km NAM Total Precipitation

Saturday afternoon-Sunday Update:
As a surface-low moves across southern Kansas on Saturday, an arctic cold front will move into Oklahoma and northern Texas throughout the day on Saturday. Temperatures on Saturday will be in the 20s/30s behind the front while areas ahead of the front will be in the mid to upper 70s! The movement of dense arctic airmasses is not particularly portrayed well by models, so the cold front may move at a faster pace than model depiction.
slide01
2m GFS Surface Temperatures: Saturday Afternoon

Behind the cold front passage, wintry precipitation may develop over parts of Oklahoma and northern Texas late in the day on Saturday into early Sunday morning. This band of snow is possible as the base of a trough approaches and strong lift occurs.
slide08
500mb GFS Vorticity Map: Sunday Morning
slide05
6-Hour GFS Precipitation Rate and Type: Saturday Evening
slide06
6-Hour GFS Precipitation Rate and Type: Sunday Morning

While adequate lift and cold temperatures will be present to support wintry precipitation, moisture will be limited. The cold front will act to scour out the low-level moisture, which would keep any snow very light if precipitation manages to develop. The GFS, and some of the other guidance, is hinting at a dusting for parts of Oklahoma and northern Texas. Please note, the map below is just showing you what the GFS is forecasting for snowfall totals this weekend. It’s entirely too early to accurately forecast snowfall totals if any at all.

slide07
Accumulated Snowfall GFS: Thru Sunday

Next Week:
Right now, the guidance is hinting at a strong upper-level low (ULL) ejecting into Texas. This scenario would create conditions favorable for increased precipitation chances, and potentially wintry precipitation under parts of this ULL. Such systems, while surface temperatures remain marginal at this time (32-35 degrees), have strong dynamic cooling. Such cooling would likely bring a wet snow to parts of the Southern Plains. It’s too early to determine the strength and track of the ULL, but I will continue to monitor this system and have updates as needed.

Again, this potential event is several days out, so a lot will change. One thing that is certain, temperatures Saturday night will be very cold across the area—windchills will be well below freezing so dress accordingly. I will continue to monitor this potential event and have updates as needed. Early next week needs to be monitored for Arkansas and northeastern Texas, but more on that later in the week.
slide10
500mb GFS Vorticity Map: Wednesday Afternoon
slide09
6-Hour GFS Precipitation Rate and Type: Wednesday Afternoon