textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 1240 PM CST Sat Jan 3 2026

* Unseasonably warm, record to near record-breaking temperatures are expected again this afternoon.

* Low, non-zero probability of mist and/or low stratus developing tonight; best chances across parts of the Lower Valley. * Fire Danger Statement in place for all of Deep South Texas with the exception of the barrier island till 6 PM CST this evening.

* A weak cool front pushes through the region tonight into Sunday with little airmass change expected.

* Overall, warmer than normal, rain-free, and at times breezy conditons with chances for patchy mist/fog at night will prevail through next week.

* Another cool/cold front approaches the region next Friday- Saturday potentially with increased rain chances and cooler temperatures.

DISCUSSION

Issued at 1240 PM CST Sat Jan 3 2026

Have decided to go with a Fire Weather Danger Statement (RFD) for much of the area till 6 PM CST this evening (see FIRE WEATHER SECTION for more details).

Low amplitude, zonal to semi-zonal (west-southwest aloft) 500 mb regime with plenty of subsidence will foster warmer than normal temperatures, mostly sunny skies, and at times breezy conditions with patchy mist/fog possible during the night across Deep South Texas and the Rio Grande Valley through the forecast period or through the first full week of January 2026.

Despite being behind the dryline and ahead of an approaching weak cool front to our north, a strengthening 585-588 dam ridge and nearing ridge axis coupled with sufficient sfc based differential heating amid mostly sunny skies, and some compressional heating (downsloping) off the Sierra Madre will yield another day of record to near record-breaking temperatures this afternoon across Deep South Texas and the Rio Grande Valley (see CLIMATE SECTION for more details). High temperatures today are progged to top out in the upper 80s to near 90F degrees, some 15F+ degrees above normal for early January.

For tonight, the prospects for mist/fog/low stratus is not as robust or promising as previous nights given the lower dewpoint temperatures following the passage of the dryline. That said, there is a low, yet non-zero probability of some mist/fog/low stratus developing tonight, particularly over the Lower Valley, where low level moisture values are higher relative to the rest of the region. BUFKIT soundings are not showing any bullish signs of mist/fog, and NBM probabilities are lower for tonight compared to last night. Nonetheless, if there is enough radiational cooling from mainly clear skies and cool advection behind the cool fropa later on, there could be some patchy mist or fog development overnight. The best chance for any mist/fog will be over Harlingen and nearby areas, where there is a low to medium (30-40%) chance. Have again applied some patchy fog in the grids primarily over the Lower Valley to take into account the potential for some mist/fog overnight tonight. Otherwise, expect for a quiet and cooler night ahead compared to previous nights.

Overall, a notable airmass change is not anticipated given how weak the cool front is. In fact, temperatures will remain above average tonight and on Sunday with overnight lows in the 50s most places and daytime highs in the upper 70s to lower 80s, respectively. No rain is expected with the ridge axis overhead.

A return flow develops out of the south-southeast Sunday night into Monday, yielding a quick return to well above normal temperatures. Rain-free, unseasonably warm, and at times breezy conditons will prevail through the remainder of the forecast period or through next Friday amid the continuation of flat ridging (zonal to semi-zonal flow aloft pattern) over the region. There may be some weak shortwave troughs around next week. However, subsidence overhead will be more than sufficient to cancel out any rainfall risks.

Medium range forecast models are depicting a cool/cold front that's expected to approach the region in the Friday evening-Saturday timeline. Early indications are that this cool/cold front will be stronger than the one coming later today and could be accompanied with higher rain chances and result in temperatures returning closer to normal levels with highs in the upper 60s to mid 70s on Saturday and lows in the 40s/50s Saturday night. Right now have low grade (20-30%) PoPs over the region on Saturday. Will continue to monitor these trends in the days ahead.

Monday through Friday of next week, daytime high temperatures will be well above normal with daytime readings topping out in the mid to upper 80s inland (70s along South Padre Island). Meanwhile, overnight lows will be in the 50s/60s across the region (mostly 60s).

AVIATION

(18Z TAFS) Issued at 1240 PM CST Sat Jan 3 2026

Through 18z Sunday....VFR conditions are expected to prevail through most if not all of the 18z TAF cycle. Later tonight, there is a low, yet non-zero probability of some mist/fog/low stratus developing. The odds are not as robust as prior nights due to drier air advecting into the region. The best chance appears to be over the Lower Valley, which includes the HRL and BRO terminals. Mist/low stratus appears more likely too than fog. Have included TEMPO groups between 08z-14z/Sun for the potential of some mist developing later tonight over HRL and BRO. Any mist/low stratus that develops will have the capabilities of reducing flight categories down to MVFR levels. Otherwise, expect for VFR conditions to prevail through the entire forecast period.

Following the passage of a dryline, winds have shifted out of the north. Expect for northerly winds 5-15 kts potentially gusting as high as 20 kts at times to prevail through the afternoon. Winds will abate later this evening/tonight with speeds up to 5 kts. Expect for winds to shift from the north-northwest to more out of the northeast in time.

MARINE

Issued at 1240 PM CST Sat Jan 3 2026

Favorable marine conditions with light to moderate winds and low to moderate seas (wave heights between 2-4 ft) to prevail through much of the forecast period. Marine conditions could become a bit more adverse with moderate seas (possibly reaching SCEC levels) Wednesday night through Thursday in response to breezy southerly winds. A cool/cold front is expected to approach the region in the Friday-Saturday timeframe. Marine conditions could become more unfavorable or adverse again during this timeframe.

FIRE WEATHER

Issued at 1240 PM CST Sat Jan 3 2026

A Fire Weather Danger Statement is in effect till 6 PM CST this evening for all of Deep South Texas with the exception of the island. Latest sfc analysis and satellite observations indicate the dryline has passed Deep South Texas and the Rio Grande Valley to the south this morning. Relative humidity (RH) values in the wake of this dryline have begun to tumble across Deep South Texas. Per the 10 AM CST observation, Hebbronville's RH values have dipped to 25%.

According to this morning's 12z BRO sounding, 925 to 850 mb dewpoints (Td) were in the single digits. Mixing has started and is expected to become rather efficient today as mixing heights increase. In anticipation for better mixing this afternoon, additional dry air advection in the wake of the aforementioned dryline, and and the dry antecedent conditions from past days/weeks across the area, have decided to issue a proactive Fire Danger Statement for all of Deep South Texas with the exception of the Island.

Texas A&M Forest Service has highlighted the entire area today under a Moderate Fire Danger Risk with a pocket of High Fire Danger across the northern half of Zapata and Jim Hogg Counties. The greatest areas at risk in particular will be along and west of IH-69C, where minimum RH values will range between 15-20%. This is the same area that's currently experiencing widespread D2 (Severe Drought) to D3 (Extreme Drought) conditions.

Winds were the greatest uncertainty and the primary wildcard in thresholds meeting elevated fire weather criteria. Forecast winds this afternoon are expected to be slightly less than to borderline criteria in general. However, there could be isolated to scattered instances (especially along and west of IH-69C) of peak winds out of the north-northwest reaching 10-15 mph withs gusts as high as 20-25 mph. Again, given the dry situation and close wind thresholds, have decided to proactively issue a Fire Danger Statement through this afternoon.

CLIMATE

Issued at 1240 PM CST Sat Jan 3 2026

A low amplitude, yet anomalously strong 582-585 dam ridge axis overhead coupled with strong sfc based differential heating under mainly sunny skies and breezy southerly winds at the sfc will support another day of record to near record-breaking temperatures this afternoon. This will be ahead of a weak cool front that will move into the region tonight.

Saturday, January 3, 2026 Record High Temperatures Brownsville: 91F in 1982 Harlingen: 86F in 2023 McAllen: 94F in 1971

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 59 79 63 83 / 0 0 0 0 HARLINGEN 55 78 59 84 / 0 0 0 0 MCALLEN 56 81 62 86 / 0 0 0 0 RIO GRANDE CITY 51 81 59 87 / 0 0 0 0 SOUTH PADRE ISLAND 66 73 67 76 / 0 0 0 0 BAYVIEW/PORT ISABEL 60 76 62 81 / 0 0 0 0

BRO WATCHES/WARNINGS/ADVISORIES

TX...None. GM...None.