Texas Winter 2017-2018

[Ntxw]

I'm starting to question the HRRR with its ice/sleet depiction. Spc meso has 850s below 0c already quickly into the Red River counties. I think it will quickly go over to all snow
0z balloon sounding will be interesting

[GeauxTigers]

Channel 5 in Dallas just gave my area-north of Denton- a little to no impact with just flurries forecast.

[gboudx]

Radar shows echos NE Dallas county into northern Rockwall and southern Collin counties. It's drizzle/light rain here. I'm in northern Rockwall county, near Collin line.

[iorange55]

DFW thinks HRRR is overdone.

"The high-res model solutions seem to have
the best handle on the current precipitation moving into northern
Oklahoma as well as the light showers currently developing across
North Texas. However, the HRRR appears a bit too wet with the air
at the top of the frontal inversion and therefore generates quite
a bit of QPF near and just south of the Red River this evening. We
will continue to favor the slightly drier solutions of the TTU
WRF and NAM with regards to precipitation tonight as they seem to
have the best handle on the dry air moving in on the west side of
the upper low."

We'll see what happens! The WRF model is slightly wetter than the NAM, which is the driest model. HRRR is the wettest. As mentioned earlier, a blend of the two probably works best.

I do find it interesting that the HRRR continues to trend wetter. You'd think as the event gets closer, it'd pick up what the NWS is saying with the dry air moving in.

[longhornweather]

Any changes for Austin area? Looked to me that some of the heavier precipitation totals were a bit further east. I was looking at a few of the most recent model runs in tropical tidbits and comparing to previous runs.

[wxman22]

Area Forecast Discussion
National Weather Service Houston/Galveston TX
357 PM CST Mon Jan 15 2018

.DISCUSSION...
It is so nice to see temperatures in the mid/upper 60s today. So
wish I could be outside to enjoy instead of bringing the bad news.
What`s that saying? If you don`t like the weather in Texas just
wait 5 minutes? That`s the forecast for tonight/tomorrow. So let`s
get to it.

Currently the arctic cold front is pushing into Red River region
and north Texas. Latest surface obs at 12Z show a 1048-1050mb high
sitting over NE Montana/NW North Dakota. Water vapor imagery shows
that nice closed low over the Great Lakes and broad vorticity
maximum over the Plains swinging southward. Upper air analysis
shows highly amplified pattern with ridge over the western U.S.
driving the polar jet due south over the Plains.

Tuesday...This is probably one of my top 5 toughest most
challenging forecasts to make and one of the toughest forecast
decisions to make. Big thanks to our forecast team collaborating
on this but 12Z models all show very similar trends. Ensembles
like SREF/GEFS seem to be showing something similar.

First thing we saw was temperatures in the boundary layer are
trending colder so we had to trend surface temperatures colder and
sooner than previous forecast. This calls for freezing
temperatures for most of the day on Tuesday with precipitation
falling.

Second the transition of precipitation types looked on track with
a transition Tuesday morning from rain - freezing rain - sleet -
snow. Model soundings from NAM/GFS show this trend. The ECMWF also
showed colder 850MB temps by 18Z Tuesday indicating a similar
trend. There is a fight between the moisture over the frontal
surface and precip falling versus the drier boundary layer air
coming into from the north. This could allow for precip to end
sooner than expected but it will have to overcome quite a bit of
thermodynamic wet bulbing to do it.

Third increase in frontogenetic lift at several levels. GFS/NAM
all show frontogenesis at 925-850mb and 850-700mb layers. There is
also jet stream configuration with the right entrance region over
much of SE Texas and quite a bit of 500-300mb Q vector
convergence supporting large scale lift. These seem to come
together a little bit late but still lift over the area 18Z
Tuesday to 00Z Wednesday. This all suggests possible banded
precipitation and you even see hints of that in the QPF output in
the models. I`m not going to get into a discussion of CSI and
lapse rates but cross sections do show pockets of CSI and steeper
lapse rates in these areas. Frontogenesis will be driving most of
the banding anyway.

Fourth we need to emphasize freezing rain/sleet as the primary
threat for most of the area. Most ice accumulations will be from a
few hundredths to a tenth of an inch. Banding could lead to
higher amounts of ice leading to need a winter storm warning. With
this potential in mind, we decided on a winter storm warning for
areas along and north of Interstate 10. Farther north there could
be a band of snow from Brenham/Conroe/Livingston north with
generally 1 inch of snow possible which would fall on already icy
conditions from freezing rain/sleet prior to snow. There very
well could be some sleet/snow late afternoon/evening in the
Houston area but freezing rain will be the main issues south of
Conroe.

Precipitation should come to an end Tuesday night with low
temperatures Wednesday morning requiring a hard freeze warning. In
the extended forecast there looks to be a chance of rain Friday
with warm air advection. This continues Saturday into Sunday with
another front pushing through Sunday. This time it looks like a
line of showers and a few thunderstorms Sunday. High pressure
builds in with more cold conditions.

Overpeck

[ThunderSleetDreams]

I know we are focused on our storm but a Huge volcanic eruption in the Philippines happened today. These things tend to have an effect on weather.

[Ralph's Weather]

The HRRR has me at 14 tomorrow as the back edge of the precip leaves me. It does seem to keep things rain freezing rain a tad too long so though it may be a bit overdone on the moisture available snow totals could still stay the same or increase.

[DFW Stormwatcher]

Channel 5 in DFW just did a pretty good synopsis of the weather situation. However, there was no real commitment to where they thought the bulk of the snow would be, a whole bunch of maybe's. Which tells me there is enough doubt to keep even professional mets from being confident. Kxas mets are arguably the best tv mets in DFW so they're lack of specifics buoys me up here in Frisco.

[bubba hotep]

FWD seems to put a lot of weight on the 3k NAM (see the other day when they issued WWA when basically only one run of the 3K supported it when basically nothing else did). 18z RGEM & GFS both look good for eastern areas of DFW. The HRRRx also continues to show this.

[Brent]

The models NBC 5 and CBS 11 use keep the snow band largely south of Dallas *shrugs*

[Ntxw]

FWD seems to put a lot of weight on the 3k NAM (see the other day when they issued WWA when basically only one run of the 3K supported it when basically nothing else did). 18z RGEM & GFS both look good for eastern areas of DFW. The HRRRx also continues to show this.

I wonder, should the nam lose this, if it did because there is no ULL lift mechanism. It performs well when you have a large ULL vorticity involved. I'm not sure of its record on isentropic lift.

[stormlover2013]

https://www.tropicaltidbits.com/analysi ... 11518&fh=6


Rgem is nice

[orangeblood]

FWD seems to put a lot of weight on the 3k NAM (see the other day when they issued WWA when basically only one run of the 3K supported it when basically nothing else did). 18z RGEM & GFS both look good for eastern areas of DFW. The HRRRx also continues to show this.

I wonder, should the nam lose this, if it did because there is no ULL lift mechanism. It performs well when you have a large ULL vorticity involved. I'm not sure of its record on isentropic lift.

Yep, they have another forecast problem on their hands...much more complicated this time around but you'd think they would've learned their lesson from hugging that model too much. Have seen it too many times over the past decade!

Tough to ignore the RAP trends

[sphelps8681]

https://www.tropicaltidbits.com/analysis/models/?model=rgem&region=us&pkg=ref_frzn&runtime=2018011518&fh=6


Rgem is nice

Awesome!! Wonder if school will be canceled tomorrow?

[Yukon Cornelius]

I know we are focused on our storm but a Huge volcanic eruption in the Philippines happened today. These things tend to have an effect on weather.

Interesting. Usually as to what sort?

[Cerlin]

Is DFW about to get duped again??? Probably no snow??

[Brent]

FWD seems to put a lot of weight on the 3k NAM (see the other day when they issued WWA when basically only one run of the 3K supported it when basically nothing else did). 18z RGEM & GFS both look good for eastern areas of DFW. The HRRRx also continues to show this.

I wonder, should the nam lose this, if it did because there is no ULL lift mechanism. It performs well when you have a large ULL vorticity involved. I'm not sure of its record on isentropic lift.

Yep, they have another forecast problem on their hands...much more complicated this time around but you'd think they would've learned their lesson from hugging that model too much. Have seen it too many times over the past decade!

Tough to ignore the RAP trends

what are the RAP trends

[gpsnowman]

I can already tell an all nighter is not in the cards for me, unless it is snowing around 9 tonight. What I might do is set my alarm an hour or two earlier than the usual 3:30. If anyone can guesstimate, about what time might we start seeing some snow fly?

[WeatherDuck]

Hutto ISD in Williamson County announced it will be closed Tuesday.