DFWWeather

On 1/16/2021 at 2:11 PM, raindancewx said:

The 6-10 day outlook from CPC yesterday looked pretty warm for Texas. Long-term, a big +SOI December value is a very strong indicator for a warm February in the South, usually including Texas. Although the signal is weaker the further west you get. December 2020 was +16, 5th highest SOI value since 1931. I don't know that winter is over in Texas, but Texas weather is pretty strongly correlated to warmth when the PNA goes in the wrong phase like it is about to.

 

The 1931-32 winter in Texas (at least for DFW) was one of the hottest winters on record. In fact, during December through February the lowest minimum temp was only 29°F. However, March of 1932 was pretty cold and we finally recorded a low of 22°F. That month there was 9 consecutive days with temps 20 below normal on average. It is pretty alarming how close we are following that winter this season. The lowest minimum so far 27°F which ties the all time hottest record for a winter season set in 2015-2016. The vast majority of our winters see the temp dip below 20°F at least one time. 

NWS office upgraded Watch to a Winter Storm Warning. They went with a Winter Weather Advisory for the Metroplex. The southwest quadrant of Tarrant is likely to see more than 3 inches and because of that, I think Tarrant County should have been included in the Warning.

After looking at all the model data this morning. Nearly every model with the exception of the ECMWF shows Tarrant County meeting criteria, at least the southwestern portions of the county anywhere from 4 inches to 9 inches in that area (though this does not account for melting). SREF Member probabilistic guidance of Tarrant county receiving 6 inches of snow is greater than 50%. Some guidance has 4 inches plus as far north as DFW Airport. The ECMWF has shifted everything out west, and appears to be an outlier at this time. If the warmer temperatures verify, then it will be closer to being correct. Therefore, I would not be surprised if Tarrant County gets added to the watch and I fully expect the Watch to get upgraded to a Winter Storm Warning this afternoon. If the latest NAM and Canadian are correct then Dallas County, Ellis, Kaufman and Rockwall would likely need to be added. This does look to be a primarily south of I-20 event, thus the further southwest you are in the Metroplex south of I-20 the better your chances of seeing the most snow. There appears to be a rapid gradient to nothing north of I-30, particularly when you get into Denton and Collin counties.

15 minutes ago, aggiegeog said:

Ok let's call it cold air then. True Arctic air would not support snow. I think its more likely we see temps dropping into the 20s under the heavy bands given the cold temps at 850 and even at 925. Daytime temps for North Central TX outside of the heavy bands will likely be 33 to 35 so there may be some melting. Under the heavy bands we are looking at >2"/hr rates with temps at or below freezing and ground temps not crazy warm given time of year and current cool temps. I am very confident in storm max totals being in the range of a foot or perhaps greater with widespread 6".

I would agree with you given the impressive cold air aloft with this setup that surface temps should be colder. I would favor temps in the 28 to 32 range during the event with that kind of cold air aloft. I mean when was the last time you saw 528 thickness over DFW (forecast from 0z NAM) and an H85 temp of -7°C with a surface temp of 37°F? Something doesn't compute.  However, given the uncertainty still in this system, I would go with about half of what you are forecasting for right now. I think 2 to 6 looks reasonable, with heavier amounts likely south of I-20 in the Metroplex. However, if the surface temps verify colder, I would agree totals closer to what you have may not be out of the question.

3 hours ago, aggiegeog said:

RGEM seems to be handling the convective nature of this event well even if the QPF may be overdone. Though around 1" QPF for a dynamic system with great moisture is clearly possible. I believe and there will be a number of areas that receive near or over 12" with the area between Hillsboro  and Nacodoches being the most likely stretch to see that. All models give this area between 0.5 and 1.5" QPF with temps supporting primarily snow.

Texas has been waiting 11 years for a Gulf surface low, potent upper low combo pumping moisture into an Arctic air mass.

First off, there is no Arctic air associated with the system on Sunday. Let's be clear on the source region of the airmass. This airmass did not originate in the Arctic circle or Siberia. It exhibits none of the properties of Arctic airmasses.  It is modified continental and Rocky mountain air. We are all excited by the snow and some impressive amounts are being forecasted by the models. However, none of that is taking into account the amount of snow that will be wasted to melting on impact. Many of the models surface temps are between 34 and 38 degrees (these may be warm given all the models H85 temps), including the NAM, during this event. If temps are being correctly modeled, It is going to be a fight to get accumulations with surface temperatures that warm. So to be realistic, I think your totals are a bit much. Even the NWS is not forecasting anything like that based from this morning AFD, thus this event may not even meet Winter Storm Warning criteria for the Metroplex. What happened in February of 2010 was extraordinary, and I would love to be wrong and it happen again, it just is not likely.

As you know, we are in the longest stretch in Weather history of no significant snow or ice for DFW (~6 years). I very much like the pattern for Sunday for a potential winter storm, probably the best setup in years. Some of our best events come form such a 500mb pattern. However, I do see caveats. To bring this into perspective, the models have a had a cold bias at this time range all winter long. I still don't see a large reservoir of cold air to tap into, thus we will need to rely on the storm to manufacture its own cold air, much like the New Year's Eve storm. I am always skeptical on this type of winter storm as 9 times out of 10, it ends up as a cold rain. Assuming the models are correct in the their temperature forecasts, this may not be much of a problem with -25C air at 500mb with system itself. The models do show colder air at 850mb over our area anywhere from -2C to -8C (depending on the model). This translates roughly to 28 to 34 degrees at the surface during the event. Should clouds clear after and we do get some accumulating snow, then we could be dealing with some of the coldest temps so far this winter. This brings me to the next caveat which is the system itself and its eventual track.  It is still out over the water, thus any deviation from the modeled track or change in timing, could greatly effect our outcome. 12z NAM looks pretty good.

Speaking of cold air...I am also liking a transition to a colder period to close out the month. I think the potential is there to tap into some bona fide Arctic air. I am starting to see some of the models latch on to this idea. Perhaps this event will be the transition?

The pattern so far this season is for all the models to have deep cold air and then back off as we get closer to the cold spell. I already see this trend starting to happen in all of the 6z models with this New Year's Eve event. While the track of the upper low is ideal, the source region and the depth of the cold have been questionable from the get go on this event. There is no true Arctic air involved. We will see how the models trend as we get closer. My gut feeling for DFW is that this is a cold rain with maybe a few sleet pellets or snow flakes mixed in.

We have a decent stratospheric warming event taking shape and 50/50 teleconnections in our favor (-AO, +PNA, -NAO) for developing Arctic cold in about 7 to 10 days. Time will tell if this can translate into some verifiable cold air. We have only hit 28°F at DFW as the coldest low and the winter is 1/3rd over.

Record cold temp set this morning at DFW of 55°F. The old record was 56°F set in 1941. If we fail to rise to 70°F (which will be close), then I believe another record will be set.

Turns out none of the models handled this cold front well at all with the ECMWF bias of hanging back too much cold air in the west as clearly evident (though it does get props for being the only model initially to show a cut-off low forming). However, that model was way too warm. Dense cold airmasses like this rarely ever get hung up out west and then retreat north as depicted on that model (extremely rare and bizarre case if that ever happens). The NAM was the only model to get it some what right, but it was even too warm on its low temps for DFW. The earlier temp forecasts of the GFS/ECMWF/GEM last weekend of 50s here was correct before they all went way too warm.

2 hours ago, cheese007 said:

Lows in the mid 50s during summer in DFW. 2020 continues to be full of surprises

Lows can fall into the 50s at DFW any month during year if conditions are right. In fact, they have fallen into the 40s in June before. Technically, we are in autumn, though not by traditional calendar standards as what most people call autumn. Meteorological fall starts September 1st. In meteorology, fall temperatures are measured from September 1st through November 30th. It has been as cold as 40°F in the month of September before at DFW. What will be far more interesting is the prospects for snowfall in the Panhandle behind this front and threat of freezing temperatures. If snow does fall, it will be the earliest ever recorded in the state of Texas and by a wide margin (record held by Stratford, Texas on September 27, 1936). A snowfall this early would truly be unprecedented. Also, any freezing temps reached would be the earliest on record for the state. This cold airmass really means business. Some models are still showing lows perhaps reaching 48 to 50 at DFW. If we fall into the 40s, it would be the earliest on record. Both daily low temp and low maximum temp records are in jeopardy both Wednesday and Thursday at DFW behind this cold front. This is really like a once in 100 year cold air outbreak.

8 hours ago, aggiegeog said:

I expect all of DFW will end up with a warning by tomorrow morning. An inch of sleet will cause huge travel issues. DFW looks top miss out on most of the snow with the majority falling between Childress and Wichita Falls and a secondary band tomorrow night from the Austin area through Deep E TX.

After reviewing incoming 12z data, I'm not so sure. I think if anything Tarrant County will be downgraded to a Winter Weather Advisory or removed from the Winter Watch/Warning altogether. There is no supporting evidence on the models to have added Tarrant to the watch in the first place (and I am still perplexed on the reasoning on that), and certainly not Dallas County. This is primarily going to stay north and west of the Metroplex.

Interesting to note on the the latest NAM 2m Temps of below zero over the deep snow pack just northwest of Wichita Falls.

13 minutes ago, cheese007 said:

Someone in the other thread mentioned a NW shift with the GFS. Seems to be a trend with the increased cold/moisture. Wouldn't get hopes up quite yet (though will agree this is the most interesting setup in years)

12z GFS is even more bullish with 7.0 inches at DFW Airport to over a foot of snow in southwest Tarrant to hardly any in southeast Dallas County with over a quarter of an inch of sleet/ice for the entire Metroplex. Low temperature of 23°F at DFW Airport during the coldest part of the event. I don't see that trend, if anything a southeastward shift of heaviest precip.

1 hour ago, BrandonC_TX said:

GFS seems quite the outlier right now, depicting a major snowstorm over the north Texas area (especially just west of DFW) on Wednesday.  Most other models (NAM, Euro, etc.) are further north.

Yes, but all of the GFS ensemble members output snow/ice for the area and over 50% of the both the 0z and 6z ensemble ECMWF members also produce significant accumulations of snow/ice for the area as well as a majority of Canadian ensemble members. The deterministic GFS is not an outlier in that respect. This is something to really watch. None of the models have done well with cold air this winter season at all and the trend here is colder. The 500mb pattern is one favorable to produce significant to even major snow/ice events in North Texas. The question is moisture/lift at the time of the coldest air and how cold the air will be. With it being nearly 80 today, temps will need to be in the 20s for this to really stick to the roads. Some models have us in the 20s for the event. The NAM is discouraging as it is cold enough, it just dry slots us, however it is know for being too dry in that time range. This is certainly the best setup I've seen in years for us.

4 hours ago, aggiegeog said:

I cannot wait for next week's front. Highs in the 70s with lows maybe touching the upper 40s here in NE TX Wed morning.

I can't either! The ECMWF and the GFS though don't seem to agree on the degree of cold. GFS is warmer and following MJO in phase 1 and 8. Whereas the ECMWF is following the recurving typhoon. Which is correct? Enjoy the relief while it lasts as it looks like we will be back above normal for much of the remainder of October, unfortunately.

DFW just had its hottest September on record out of 121 years of weather records. 86°F was the average temp (normal Sept average is 78°F). Though ironically we did not set any high temperature records. We never fell below 70°F which was first for the month and we had the most 90+ degree days of any prior September. It was also the only September on record with no measurable rainfall. Far cry from last year when we recorded 12.96 inches of rain which was the wettest September on record.

September Climate Statistics for DFW:

We are approaching the autumnal equinox and DFW Airport has failed to record one single low temperature below 70°F. Looking at the models to the end of the month, it doesn't appear that we will get to 70°F or below anytime soon. Out of 121 years of records, that has NEVER happened. Only 15 years of the 121 year record period have we seen Septembers where the low failed to fall below 60°F which is kinda of a benchmark for a warm September. Roughly 60% of the time, DFW has fallen below 60°F at least once during the month of September. Roughly 30 of the 121 years of records, the temp has fallen to 50°F or below at least one time in September. This September is on track to the be hottest September on record for DFW, and while daytime temps have been hot and slightly above normal, there have not been any daily record highs tied or broken. It is all because of the low temperatures. Normal lows this time of year should be in the 65°F to 67°F range falling to 62°F by the end of the month.

So far, the 2018-2019 winter is the 5th warmest on record at DFW. This is a far cry from all the forecasts calling for temps this winter to be 1 to 3 below normal across Texas. Complete dud of a winter. I wonder if there is still time for us to get some bona fide Arctic air down here? The lowest temps so far this winter was way back in November (technically not even winter) of 25°F.

On ‎1‎/‎30‎/‎2018 at 12:42 PM, aggiegeog said:

Umm, the most extreme 12Z GEFS member is showing lows on the 12th way below 0 (-20s in NE TX) with even some sub 0 highs. Lets hope we can toss out that possibility, but mean lows around 20 for days 10-16 is still crazy. Thursday morning is the only morning in the 16 day run with a mean low over 39. Wish there was more precip showing up, but that's life with persistent cold NW flow.

In all of weather records kept for North Texas area, the above scenario as has never occurred, so that was an easy disregard. Even during the severe Arctic outbreak of 1899 (coldest on record for this area), it wasn't that cold.

Nearly all of today's guidance unanimously is backing off on any Arctic air intrusions over the next couple of weeks, despite the -EPO and MJO phases, the abundance of cold air in Canada, and the highly amplified flow H5 pattern. Our best chances to see Arctic air intrusions are this Sunday 2/4 and again around 2/10. I'm not sure I totally buy off on this yet (especially for the 2/10 period), but it is sure looking like most of the cold air will be kept well north and east of Texas this go around. The operational models have not handled any of our cold air intrusions this winter well at all, and it could possibly change.

Officially, the NWS is saying the low today at DFW Airport (KDFW) was 13°F. However, the 5 min metar observations data shows that the site hit 12°F at 5:20 am, 5:25 am, 5:30 am, and 6:45 am. The former we have hit 7 years ago, but the latter would be 22 years. What would be the reasoning on this?

If DFW Airport reaches 12°F or lower as forecasted...then that will be the coldest we have been in 22 years. You have to go all the way back to February 1996 when we hit 8°F. Doubt we will hit the single digits, but we could. This current streak is the longest on record by a wide margin of not falling below 10°F.

We are going on nearly 3 consecutive years without any significant snow or ice. Last event was March 4, 2015. By significant I mean 0.25 or greater of ice or 2 inch or greater of snow. If nothing occurs this year, it will be the longest stretch since 1978 without any significant snow or ice for DFW, possibly longer.

28 minutes ago, aggiegeog said:

I fully respect the NWS and the FTW office in particular is typically great, but the probability chart they put out regarding the winter storm threat being very low is as reckless or even more so than some nobody trying to hype the storm. This storm needs to be taken as seriously as if there was a hurricane being modeled to hit within a week.

I agree, especially given that this is a Holiday impact storm with heavy travel. However, I understand their caution. There is a lot of chaos in the modeling, though, and none of them agree. The deeply negative EPO and the strong MJO phase 7 and 8 argue for deep cold in the southern plains. If we get moisture on top of this, it could get ugly. By the way, I kinda feel the GFS is outperforming the ECMWF this fall. The GFS did a better job with the cold and snow earlier in the month. I think the 0z runs ECMWF is strange hanging the cold up in the Rockies and spilling westward, and delaying it until after Christmas.

8 hours ago, aggiegeog said:

We are now within 10 days of a potentially historic Arctic outbreak. I don't think I could dream up more ideal conditions than what the GFS had been showing for the last 4 days and now we are in the range of the other global models. GFS now shows the NPO ridge inn the GoA reaching into the 590s at 500 mb. That is levels we see in July here. That will likely lead to 1060s mb highs in MT around New Year's. This will also bring precip as we will be on the southern periphery of the upper trough.

I'm liking what I'm seeing in terms of major cold getting here. The 500 mb heights certainly support some massive dump of cold air. Been watching the ECMWF for several runs and it has bee bringing -40°C plus air at H85 into the Great Lakes or just north of there for several runs (I think one run actually on the control got to -45°C). That is quite possibly the coldest air I ever seen on that model. Most models agree the leading edge of an Arctic airmass will make it into North Texas about Friday before Christmas. It is after this they diverge quite a bit. The ECMWF pushes deeper with the trough similar to last time pushing the storm track well south of DFW or North Texas. The latest 6z GFS today is a winter weather lover's dream with nearly 5 days of snow and ice (mostly ice). The 0z wasn't too shabby either. However, this is still several days out and we have been in a massive drought. Like the forecast saying goes, "when in drought leave it out!" Given the upper air pattern I would tend to favor the ECMWF right now. Regardless, the cold is coming, potentially even severe cold! 

1 hour ago, aggiegeog said:

Keeping an eye out for a possible, if unlikely, 1993 late October setup. Anyone up for some October snowflakes and freezing temps?

Glad you brought this up! I've been looking at the same data. Ironically, ECMWF doesn't seem to be quite on board yet with a more slanted trough east of us driving the core of the cold east, which has me very cautious. However, CMC and GFS have been gung-ho about a big cold air outbreak the weekend of the 28th for several runs now as with many ensemble members. Generally, all of next week should be the coolest of this October with the potential of 3 fronts, one this weekend, one about Tuesday, and potential big one the last weekend of the month. All of this will of course be driven by the potential recurve of what should be a super typhoon toward Japan in Pacific. This typhoon should recurve because of the record phase 5 MJO. In fact, the recurve should be a lock! This will drive the 500mb pattern change over North America. Regarding precip chances with this, much too early to tell, I'm not sure on the pattern quite yet.

Today's 0z and 12z ECMWF and the 12z GFS are jumping on board to a major Arctic air intrusion into Texas around Feb 8th time frame. CMC looks like it is on board as well. The MJO looks to be heading to phase 8 about that time. What do you all think?

36 minutes ago, Quixotic1 said:

Winter is on deathwatch. 

I know it is on hiatus now, but the cold is definitely coming back in some fashion. Despite the positive PNA, the latest 2mb warming episode over the pole and the epo trending negative towards the end of the month and the NAO trending negative all point to the cold coming back end of next week into week one of February east of the Rockies. MJO in phase 1 and 8? Also, looks like a favorable 500mb pattern for snow and ice for us. Both the long range ECMWF, GFS, and CMC all support this idea. Check out latest 8 to 10 day 500 mb means. Arctic may even overtake the eastern 2/3rds of the CONUS by mid February.

18 minutes ago, jhamps10 said:

12Z GFS showing 7-8" of rain right on top of Collin County. One feature I have noted is that the Longer range NAM and the GFS are a good 50-60 miles apart when it comes to the cold front. Probably wont end up being a big deal here, except for maybe thunderstorms at 65 vs a cold rain at 40

When has there ever been that much rain in a single system in January at DFW? Also, NFWD talks about Arctic front stalling in the area. Again, when has that ever happened in January? The models are either not handling cold air well and it will push on further south, or not make it here at all.

The 0z ECMWF has backed way off on the cold air resulting in nothing more than a cold rain for this event for nearly all of North Texas. It even loses the connection to deep Arctic air. Not impressed with this run at all.

6z GFS is also backing off on the cold air with all frozen precipitation west of the Metroplex during the entire event.