A cold front has moved through the entire forecast area. Moist flow running atop the cooler air at the surface has led to cloudy skies today. A disturbance will be approaching the region tonight from out west spreading lift across the area. PWATs (precipitable water) values are expected to climb to 1 to 1.5 inches across the area. This will lead to numerous showers to develop tonight into tomorrow night. This is not expected to be a widespread heavy rain event as all precipitation is expected to be light to moderate. Rainfall amounts will vary from as little as .10″ to just over an inch in the immediate DFW Metroplex. Heaviest totals will be to the south and east of the Metroplex. Precipitation is expected to end from west to east Wednesday night. Cold air advection, clouds, and rain will keep temperatures in the 40s all day tomorrow. Lows will drop into the upper 30s and lower 40s for Thursday morning. Another cold front with more shots at rain is expected this weekend.

Forecast rainfall totals for Wednesday, November 8, 2017

Hurricane Irma, still days away from making landfall on the continental United States, is not a threat to the Texas coast, despite the garbage being disseminated on social media. In fact, there is not a computer model forecast that takes Irma into the Texas coast. Irma will likely be our next major hurricane in the Atlantic basin possibly reaching Category 5 strength, but as stated, she is days away from reaching the United States. There is another area of disturbed weather coming off Mexico that may be a potential tropical threat for the Gulf in about 6 to 10 days. This may bear watching; however, we have a pretty stout cold front coming down the Plains next week that is expected to make it out into the Gulf. This front will effectively act as a barrier wall for Texas against the tropics. This front may bring a quick shot at rain as it barrels through North Texas Tuesday evening. Winds will turn out of the north around 20 mph or so and be quite breezy behind this front. Temperatures will feel more autumn like by Wednesday and Thursday of next week. Much of North Texas is expected to fall into the 50s by Thursday morning as much drier and cooler air is advected into the region.

While it feels cold outside this morning with temperatures in the 30s, wind, and patchy areas of drizzle, it will be nothing compared to what is coming this weekend. Today will struggle to warm under mostly cloudy skies with temperatures topping out in the mid 40s. A rapid warm-up will commence tonight as an intense warm air advection pattern unfolds out ahead of the next trough. Temperatures will actually start out colder and warm steadily through the night. Actual lows for tomorrow will probably occur closer to midnight than sunrise.

Warming will continue to take place through tomorrow as temperatures soar into the 70s. This will be short lived as powerful Arctic air mass is dislodged and plunges deep into Texas on Saturday. Timing of the front is somewhat hard to ascertain as these Arctic air masses always move faster than guidance. The current thinking is that the front will arrive sometime around midday Saturday. Temperatures should be able to warm into the 60s ahead of the boundary, possibly warmer if the front’s timing is later. Then there should be a drastic temperature drop behind the front. Guidance continues to trend colder with this air mass, and DFW Weather now is forecasting lows in the teens both Sunday and Monday mornings. Highs will struggle to get out of the 20s on Sunday, if at all, even under full insolation. It will also be windy with gusts to 35 mph possible. This will be put wind chill values in the single digits Sunday morning with wind chill values close to zero or below near the Red River. Wind chill values will remain in the single digits and teens throughout all of Sunday.

On Monday, temps will struggle to reach freezing, if at all, again making for another very cold day. Another cold night can be expected on Tuesday with morning temps bottoming out in the lower 20s once again.

Regarding the potential for wintry precipitation, it is looking much too dry at the surface and in the dendritic growth zone for snow crystal production. However, with these cold air masses, we cannot entirely rule out some patchy freezing drizzle or a flurry or two, but nothing significant. This is mostly likely to occur Saturday night early Sunday morning before the moisture is really scoured out, though most will see nothing.

Residents of the DFW area should prepare now for a prolonged period of subfreezing temperatures by winterizing their homes (wrapping pipes) and taking necessary precautions for outdoor animals and sensitive plants.

Get ready for a wet weekend followed by a substantial blast of Arctic air by next Wednesday. An upper-level storm system, deepening out west, will become a cut-off upper-level low over Mexico before lifting northeastward on Monday. At the surface, a reinforcing shot of colder air will spill southward. This will make for a wet, chilly, day on Saturday with temperatures likely not getting out of the 40s all day. Combined with northeasterly winds of 15 to 25 mph, wind chills will likely be in the upper 30s at times. Persons attending any outdoor sporting events will need to be prepared for wet and cold weather. This upper-storm system is already spreading moisture northward into Texas today. This will set the stage for a widespread rain event beginning as early as later this afternoon/evening and lasting through Monday.

The heaviest rains will come later tonight into Saturday as the first disturbance moves northeastward from this system. At this time, very little convection is expected, though we cannot entirely rule out a lightning strike. No severe weather is expected with this system. Rains may taper off a bit Saturday night into a good portion of Sunday, though some patchy drizzle/mist cannot entirely ruled out during this time frame. Rain chances will increase again on Sunday night into Monday as the main upper-low traverses over North Texas. This will bring the best chances at seeing convection. Widespread rain totals of 1 to 3 inches can be expected across the forecast areas with the heaviest totals off to the southeast.

After this system passes off to the northeast, our attention will turn to the north as the Arctic gates swing wide open. A very intense Arctic air mass will plunge southward reaching North Texas sometime on Wednesday. The front’s timing is still uncertain this far out. Very cold air will spill southward from eastern Alaska and the western Northwest Territories seeded from air originating from Siberia. Some models are going to a full blown McFarland look to the upper air pattern and driving the surface front as far south as Central America. This will definitely be colder than anything experienced last winter. There is no evidence that suggests any ice or snow with this Arctic intrusion as it looks quite dry. This portion of the forecast will continue to be refined as more data becomes available.

UPDATE: The forecast below is largely unchanged. For this update though, the frontal timing will be adjusted a bit to reflect the latest data. The front is now expected to move across the DFW Metroplex on Sunday in the late morning to early afternoon timeframe as opposed to Sunday night. We are still expecting a decent rain event into early next week, with rain chances now extending into Tuesday. There should be widespread totals by Monday of 1 to 3 inches of rain with locally higher amounts possible.

Although today is the autumnal equinox, it will still feel like summer with above normal temperatures with highs well into the 90s continuing today. Though, we should thankfully not see any more triple digit heat like earlier this week. However, there are some big changes coming our way.

• Moisture will begin to increase tonight in response to storm system forming out west.
• Showers and thunderstorms will be on the increase tomorrow, mostly along and south of I-20, in response to the storm system moving out of the Rockies onto the Plains.
• Showers and thunderstorms become more widespread on Saturday through Sunday.
• PWATs increase to 2+ standard deviations above normal, setting the stage for bouts of heavy rain Saturday night through Sunday.
• Strong cold front expected to arrive Sunday night (though timing could change). This will be the first significant cold front of the fall season.
• Discrepancies between the ECMWF and GFS models, with the former cutting off energy and hanging it back, dictate when precipitation will shut off, regardless substantially drier and much cooler air will move in behind the cold front. Rain may linger into Monday per ECMWF which may effect degree of cooling of temperatures.
• Widespread 1 to 3 inches of rain expected by Monday with locally higher amounts possible.
• Temperatures behind the front should cool to the 50s in many areas for the first time this season with highs in the 70s.

The forecast could obviously change given the discrepancies among the ECMWF and GFS, especially with ending of rain and amount of cooling of the temperatures behind the front. Overall, the theme of a wet weekend and much cooler weather early next week is looking likely no matter which solution verifies.

Yesterday, the mercury hit 100°F at DFW Airport on southwesterly winds. I really thought we would get through the rest of our hot season without hitting triple digits one more time, as that wasn’t readily apparent in the overall synoptic pattern. Today, the winds should be more southerly/southeasterly, H5 heights a little lower, and H85 temps a degree cooler as a result. This may help to keep temperatures below 100°F today, especially with the 0.35 inches of rain received yesterday at the airport, but it will again be close. Heights over all should continue to weaken as we head through the rest of the week. Moisture will begin to advect northward on Thursday, thus after another hot day on Wednesday, temperatures should be slowly coming down.

The guidance (both the GFS and ECMWF) are coming into better agreement with the pattern for next week with more rain opportunities beginning as early as this weekend. Both show the first significant cold front of the autumn season next week, but with slight timing differences. This is something I have been watching since the cool down earlier in the month didn’t pan out, and I suspected that our next big shot at cooler air may come the last week of September. The ECMWF weeklies have been locked on to this for a while now. This will be something I will have more details on through the week as better data become available. It should be noted that if the current guidance holds, it will be significantly cooler to close out the month of September.