Category Archives: Forecast Blog

WINTER TO FINALLY ARRIVE IN NORTH TEXAS

Satellite image for December 24, 2015 depicting next potent upper-level storm system, to affect the area the weekend after Christmas, coming ashore in the Pacific northwest.

For those wanting a taste of winter, the exceptionally warm weather we have been experiencing for the last several weeks is about to come to an abrupt end. Unfortunately, this will not be in time for Christmas. Expect unseasonably warm conditions to persist the next couple of days.

A strong upper-level storm system is now entering the Pacific northwest. This will be our next major weather maker for not only us, but much of Texas as well. This system is expected to dig down into the desert southwest and strengthen and become a closed low. It will continue digging into northern Mexico, and then, swing east northeast across Texas over the post-Christmas weekend. A deep trough will envelop much of the Western CONUS and allow a big chunk of Arctic air to spill southward along the lee of the Rockies. This strong, Arctic cold front will begin moving across Texas on Saturday and reach the DFW area in the very early hours on Sunday morning while spreading a shallow, low-level Arctic airmass in its wake. The coldest air so far this season will follow the passage of this front and bring an abrupt end to our warm weather pattern.

Out ahead of the upper-low, strong southwest flow aloft and southerly flow at the surface will advect warm moisture laden air into the region. PWATs (precipitable water) will climb to the 99th percentile for late December across the area. What this means is the potential for another very heavy rainfall event for our area on Saturday into Sunday. It is too early to pinpoint exact amounts, but rest assured it does look like another multi-inch rain event for our area. This will promise to bring already extraordinary annual rainfall totals above the 60 inch mark for DFW. In addition to the heavy rainfall, areas east of the I-35 corridor will have the potential for severe weather with this system. Nearly all modes of severe weather will be possible. More details on the severe weather will unfold in coming days as we have a better idea of mesoscale parameters.

While we have rain in our area, much of west Texas will be experiencing what may become a historical blizzard for that region. Very heavy snowfall is expected in that part of the state with some potential for major accumulations. Near blizzard to blizzard conditions will be possible across much of West Texas from the Permian Basin into the Texas Panhandle. Winter Storm Watches have already begun posting for that part of the state. Travelers heading into that region should be extremely cautious of the weather and plan to make alternative travel plans.

The snow may begin to spread into the western half of North Texas Sunday night into Monday, as the cold air deepens in our area due to the track of the upper-low passing nearly over top of the area. Rain may begin to mix with or change to snow as far south as the DFW area during this time frame. This is all dependent on the exact tract of the low and where the dry slot sets up with this system. Any deviation to the northwest of the tract of the low will keep the cold air warm enough for the precipitation to remain all liquid in our area. If the low moves further south or southeast, then a changeover to all snow could produce some minor impacts to our area. Stay tuned as this part of the forecast could change significantly.

Lows by Tuesday morning will likely drop into the 20s most areas with temps struggling to make it into the 40s for Monday and Tuesday.

SEVERE WEATHER THREAT TODAY

A rather strong shortwave trough will approach the area this evening on a negative tilt providing lift for scattered convection across the area. The latest hi-res models are keeping most of the storms that fire with this disturbance east of the Metroplex, but there is a marginal threat for severe weather for any storms that can overcome the cap. For the Metroplex, the storms look to be mostly elevated limiting the severe weather threat, provided the cap can be breached. Strong to severe storms are possible with the main threats being damaging winds around 50 mph to 60 mph and moderate sized hail. As the storms push east, or further eastward development occurs, conditions are little more favorable for severe weather as the storms can become surface based. Adequate instability in the 1000 to 2000 J/Kg range and shear combined with lapse rates in the 6 to 7 C/km range leads to a slight risk area for severe weather. Storms will be able to produce damaging winds in excess of 60 mph, large hail, and pose an isolated tornado risk. This slight risk is noted in the orange color in the map below and should mostly be east of the Metroplex. As this disturbance races off to the northeast, the threat for storms will diminish after 3 am.

Severe weather threat for Tuesday evening, December 22, 2105

POST CHRISTMAS 2015 STORM TO BRING ANOTHER ROUND OF RAIN TO THE AREA

Stubborn pattern over the United States that has what cold is available in the west and warmth for the eastern half of the country. This pattern has been dominant for much of December and will continue through Christmas with near record heat in some places.

For those hoping to see some actual winter weather or temperatures this year for Christmas are going to be very disappointed. Temperatures well above normal will be the rule this week as with much of December 2015. In fact, December 2015 is in the running of being the all time hottest December on record for DFW. As has been the case this year, intense southern stream storm systems have brought copious amounts of rains to the area. It looks like the storm system we are watching post Christmas will be no different.

In the meantime, there a couple of smaller features to discuss in the short-term. Today, a weak cold front will push the soupier air and fog from this morning southeastward as it sweeps across the area. This will allow clouds to clear and temperatures to fall into the 40s overnight (still well above normal for this time of year). Tomorrow morning will likely be the coolest morning of the week. The radiational cooling setup tonight combined with light winds and lingering moisture will set the stage for the potential for fog tonight after midnight. Some of this fog could be dense and may take sometime Tuesday morning to burn off.

A weak short wave trough will dive out of the Rockies into the Central Plains Tuesday and rapidly intensify. This will draw the soupier air back over DFW by Tuesday afternoon, setting the stage for scattered convection from the I-35 corridor points eastward by early Tuesday evening. The official forecast will carry POPs at 20 percent to account for any storms. Any storms that form will have the potential to become strong to even severe as 1000 to 2000 J/Kg of CAPE can be realized by Tuesday evening across the area. Any severe storms would be capable of damaging winds and the threat of moderate to large hail. An isolated tornado threat cannot be entirely ruled out east of the Metroplex, but the tornado threat looks low. Storms will quickly move eastward as the shortwave lifts northeast away from the region.

In its wake, southwest flow aloft will dominate out ahead of potent storm system that moves onto the Pacific northwest. This system is expected to dive into the desert southwest and intensify while becoming partially closed off. The computer models diverge substantially in the handling of this system, but it looks like it will be our next big storm system post Christmas. Warm air advection showers will begin to break out across the area as early as Christmas Day afternoon. This system will have a good fetch of moisture to work with, given the long stretch of southerly flow ahead of it, bringing with it a potential for heavy rainfall as a rather strong cold front dives in from the north on Saturday. It is too soon to tell how much rain we will get, but it does look like at least enough to send us over the 60 inch mark at DFW for the year. This system will need to be watched closely for heavy rainfall leading to more flooding problems and if the precipitation shuts off before the significantly colder air arrives. Stay tuned for inevitable updates to this forecast as the week progresses.

RAINFALL RECEIVED ACROSS THE AREA

Below is a snapshot of rain totals received since our rain event began yesterday, December 12, 2015. Overall forecast values were a little bit lower than forecasted for the central portions of the Metroplex. Western sections did well by staying at an inch or less. Eastern sections stayed between 1 and 2 inches, and the much heavier rains were east of the forecast area as predicted. Of note, Gainesville, TX has hit a whopping 80 inches of rain for 2015 – truly incredible!

Rain received across the forecast area as of 7:00 am December 13, 2015.

AND THE RAIN RETURNS TO DFW THIS WEEKEND [UPDATED WITH FORECAST AMOUNTS]

12/9/2015 Current satellite image of next storm system and path.

After a good reprieve from the excessive rainfall over the Thanksgiving Holidays, rain will return to North Texas this weekend. Rain chances will be highest on Saturday evening into Saturday night. The greatest threat for flash flooding will be along and east of the I-35 corridor where the heaviest rains fell last time. Grounds are still saturated from the last event, and coupled with the dormant vegetation, flash flooding will be a real concern. Instability with this system will be small with high shear, thus a rogue strong to severe storm cannot be ruled out.

A warm air advection pattern will continue through Saturday as southwest flow aloft prevails across the area out ahead of the storm system. This will advect moisture and ridiculously warm temperatures into our area. In fact, they will be downright hot for December. Highs on Friday may flirt with the record high at DFW which is 80°F set in 1938 and 1996. This will be highly dependent on cloud cover and moisture, thus the dfwweather.org forecast has officially kept highs just shy of the record. Overnight lows will be well above the normal high for early December Friday night (in the low to mid 60s) which is about 59°F. These temperatures are nearly 30 degrees above normal for this time of year. A Pacific cold front will push across the area Saturday night and this will be the main focus for shower and thunderstorm development. Some lingering rain showers behind the front may be possible on Sunday, especially if the slower ECMWF scenario pans out. Otherwise, temperatures will return to more seasonable levels behind the front with lows in the 40s and highs in the 50s.

It is too early to forecast rain amounts with the weekend system, but early indications are that amounts will generally be around an inch or less. It must be stressed, we are not expecting anywhere close to the amounts received over Thanksgiving.

We will be watching another storm system taking shape for next week that may bring even more rain to the area.

DFW Weather forecasted rain amounts through Sunday 12/13/2015.

3 TO 5 INCHES OF RAIN EXPECTED BY SUNDAY AT DFW MAKING FOR THE WETTEST YEAR ON RECORD

A very wet holiday weekend is in store for much of the area. In fact, we are expecting 3 to 5 inches of rain across the area by Sunday. If this forecast verifies, this will make 2015 the wettest year on record at DFW. Currently, DFW is the 3rd wettest year on record with 50.75 inches of rain officially recorded. Only 1991 (53.54 inches) and 1932 (51.03 inches) are wetter. Thus, DFW only needs to pick up 2.80 inches of rain to break the record. We should out do that by Sunday with December left to go!

A large upper-low will move down from the Pacific northwest and carve out a deep trough over the western CONUS. This upper-low will become cut-off from the mean flow and slowly migrate eastward over the holiday weekend. At the same time, the deep trough will allow cold, Canadian/Arctic air to spill southward. This cold airmass will be very shallow in nature and move southward via cold air damming processes along the lee of the Rockies into Texas against southwest flow aloft. The coldest air will become entrenched across West Texas where temperatures will plummet below freezing setting up for a period of icy weather this weekend. Strong southwest flow aloft will moderate the cold air as it moves into our area. Thus, temperatures are expected to stay above freezing leading to a cold rain event at DFW. The heaviest rains will occur ahead and along a strong cold front expected to plunge through the area Friday morning. PWATs (precipitable water) are expected to climb as high as 1.75 inches during this event, which is in the 99th percentile for November. In addition, additional moisture will be advected over Texas from the remnants of tropical cyclone Sandra in the Pacific basin. All this points to a heavy rain event across the area. We are not expecting severe weather or wintry precipitation with this event, at this time.

Moisture and warm air advection should intensify today and tonight and become strong enough for areas of drizzle or light rain this evening into tomorrow. An increase in clouds and temperatures through Thanksgiving Day will be possible as this process intensifies out ahead of a strong cold front barreling southward. Precipitation chances increase later on Thanksgiving Day as lift begins to encroach on the area as the cold front moves southward. Rain showers, heavy at times, and few claps of thunder will be possible out ahead of, along, and behind the front as it moves through the area. Additional rainfall will be possible on Saturday through Sunday as the dynamics arrive from the remnants of tropical cyclone Sandra. By Sunday, we should pick up 3 to 5 inches of rain across the area. The upper-low should be moving out east across the Plains pushing the trough out of the area ending all rain from west to east on Sunday/Sunday night.

POTENTIAL FIRST FREEZE/FROST THIS WEEKEND [UPDATED]

UPDATE: The latest data continues to deepen the cold air behind early Saturday morning’s strong cold front (as discussed below). The airmass behind this front is going to be continental Canadian with H85 0°C line now projected to reach as far south as the I-20 corridor. This should promote widespread light freezing conditions across the northern half of the forecast area by Sunday morning. As a result, temperatures have been lowered Saturday into Monday. Temperatures may actually stay in the 40s for much of the day on Saturday with blustery north winds up to 35 mph and struggle to reach 50°F on Sunday. Clear skies and lighter winds will promote excellent radiational cooling potential Sunday morning with lows north of I-20 around the freezing mark, including DFW Airport. The colder spots may dip into the upper 20s. This is a good time to start winterizing your homes and taking precautions for sensitive vegetation. This cold snap will likely end the growing season for much of the area. There may be periods of light rain or drizzle on Saturday morning behind the front, but with the Gulf remaining shut off, precipitation looks rather meager at best and amounts will certainly be light.

The long range models continue to waffle back-and-fourth in the extended. There still seems to be signs of the possibility of an Arctic air intrusion around or just after the holidays . . .

High pressure will build in behind the departing low pressure and Pacific cold front today. The pressure gradient will tighten today from the building anti-cyclone and departing low pressure causing west southwest winds to gust to around 30 mph this afternoon, making for a windy day. The winds should decouple after sunset and allow temperatures to fall into the 40s everywhere overnight. Winds should stay up just enough to prohibit fog formation. Temperatures should remain seasonable through the end of the week with lows in the 40s and highs in the upper 60s to around 70°F, which is somewhat typical for this time of year (maybe a little warm on highs).

A stronger cold front is expected to arrive Saturday. Gulf moisture looks to remain cutoff from this front, so precipitation looks minimal. However, a very chilly airmass will advect in behind this front with H85 temps approaching 0°C. This will allow temperatures to plummet into the 30s area wide by Sunday and Monday mornings with highs only in the 50s. This will likely set the stage for the first frost of the season for the DFW Metroplex. Most likely, the cooler spots outside the urban heat island may even experience a light freeze. The average first freeze for DFW is November 22nd.

There are signs, and the ECMWF has been hinting at this for several runs, that the Arctic may open up just in time for the Thanksgiving holidays. The EPO (Eastern Pacific Oscillation) is projected to turn negative which is an indication of troughing across the central/eastern CONUS. The ECMWF continues to build an Arctic airmass in British Columbia and Northwest Territories seeding it from cross polar flow from Siberia. Then, spills this southward into the Plains and eastward over the holiday weekend or just after. The GFS has also shown some signs of this in the past several runs, however, the latest 0z run does not show this at all. This could be a very interesting thing to watch over the coming days . . .

OUR NEXT STORM SYSTEM APPROACHES

DFW is bracing itself for another round of rain, some of which could become heavy, especially very early Tuesday morning.

For Today (Saturday), a disturbance in the mid-levels of the atmosphere will be approaching from the southwest. This disturbance is already responsible for some convection upstream in the Trans-Pecos region. As it moves toward North Texas, it will help saturate the mid-levels of the atmosphere. However, it will be encountering increasingly drier air across our region, especially at the surface where dewpoints will largely remain below 50°F. As a result, think that any precipitation that forms will largely fall in the form of virga, rain that evaporates before reaching the ground. This will play havoc on high temperatures today. I think DFW will have a chance to warm into the 60s as the effects of the disturbance may not arrive in time to offset diurnal warming. However, the further southwest one goes, temperatures may be affected and some areas may fail to get out of the 50s today. The official forecast will call for occasional sprinkles today across DFW, maybe increasing to light rain tonight as the lower levels saturate. Rain amounts in general should stay at or less than 1/10 of an inch.

There should be a reprieve in any precipitation early Sunday morning as we await the dynamics from the approaching trough and strong upper-air disturbance. Rain should gradually increase from west to east Sunday as the system approaches. By Monday afternoon shear and instability increases and there could be a stronger storm or two. PWATs will also increase substantially by Monday night, as a squall line begins to take shape along a dryline/Pacific cold front racing fast across Texas. Some strong to possibly severe storms will be possible with this system, the main threats being from heavy rain due to higher PWATs, straight line winds, and possibly a spin-up or two. The squall line is not expected to reach the Metroplex to around daybreak Tuesday morning, thus the morning commute could be a wet one. The dryline/Pacific cold front pushes through Tuesday morning, thus I expect all of the storms to be east of DFW by 8:00 am ending all precipitation chances. The pressure gradient will tighten between the building anti-cyclone behind the front and departing low pressure system making for another windy day on Tuesday. Winds could gust in the 30 to 40 mph range. Seasonable weather will ensue the remainder of the week. Though I will stress nothing out of the ordinary by any standards, so expect temperatures to remain at or above normal for November. Early indications are that we could pick up 1 to 2 inches of rain by Tuesday.

Another cold front and system will bring the next chance at showers and thunderstorms by next weekend.

FORECAST UPDATE: STORM THREAT DIMINISHES – DRYLINE THROUGH MUCH OF THE METROPLEX

Today’s thunderstorm chances are rapidly diminishing as storms march eastward along with the dryline and cold front close behind. Strong, westerly, downsloping winds are increasing behind the dryline as the low pressure system deepens as it marches eastward across the central Plains. These strong downsloping winds will help temperatures soar to near record levels today. The record high temperature for today at DFW is 85°F set in 1911. Forecast highs were raised a bit after temperatures soared to the forecasted high of 83°F from this morning’s issuance. Winds will gust to near 35 mph behind the dryline making for a quite windy afternoon. Our winds will switch to the northwest this evening where they should decouple a bit after sunset. The much drier air will allow temperatures to cool efficiently this evening with overnight lows expected in the 40s area wide. We should be much cooler tomorrow with highs only reaching the mid to upper 60s.

We are still watching a southern stream system that could affect our weather as early as Saturday night with more chances of showers and thunderstorms, especially on Sunday and Monday. An even stronger system may be on tap for later next week.

AN ACTIVE PATTERN CONTINUES FOR DFW

A rather active weather pattern will continue through this week for DFW. Our next system to affect the area will arrive on Wednesday in the form of a Pacific cold front. The low pressure associated with this system will eject from the four corners region onto the Central Plains rather quickly. Scattered showers and a few thunderstorms will be able to form in the warm air advection pattern out ahead of this system as early as Tuesday night. However, our best chances for rain will come Wednesday morning with the passage of the cold front. At this time, given the timing of this system, speed, and lack of instability aloft, severe weather is not expected for the immediate DFW Metroplex. Rain amounts will be rather limited as well given the speed of the system. Winds behind the cold front will be quite strong bringing much drier air into the region. Winds could gust in the 30 to 40 mph range on Wednesday afternoon. The cool air associated with this frontal passage will not actually truly be felt until Wednesday night into Thursday morning where overnight lows will drop into the low to mid 40s area wide.

Another system will approach the area by next weekend brining our next bout of rain, especially on Sunday. This system may become detached from the mean flow and be a less progressive system.

There is still no indication of any truly cold air or freezes coming our way, at least not in the next ten days.