textproduct: El Paso

KEY MESSAGES

Updated at 1159 PM MDT Sun Sep 20 2026

- Quiet and warm weather will continue for the next 36 hours or so.

- An early season back door cold front will interact with a late season monsoon moisture surge and bring widespread showers and thunderstorms to the area Tuesday afternoon through Wednesday afternoon. Localized flash flooding will be a risk over a large portion of the area.

- The main concern is that a narrow axis of more persistent thunderstorms and particularly heavy rainfall amounts will set up somewhere in south-central New Mexico or Far West Texas, with higher impact flooding Tuesday night into Wednesday morning. This could include the Mesilla Valley and El Paso area, though there is considerable uncertainty in exactly where this narrow axis will set up.

DISCUSSION

Issued at 1137 PM MDT Sun Sep 20 2026

Fairly quiet through early Tuesday, with just a slight chance of a few showers and thunderstorms in the Bootheel on Monday, spreading a little north and east Monday night. But the pairing of an early-season back door cold front and a late-season monsoonal moisture surge will result in some big changes Tuesday through Thursday.

The first piece of the puzzle will be a backdoor cold front pushing into the Sacramento Mountains by around midnight Monday Night/Tuesday morning, and reaching the Rio Grande by dawn. NBM tried ramping up higher PoPs in the Sacs a little too early. It looks like fairly shallow moisture will result in fog and low stratus advecting up to the main ridgeline in the Sacramentos Monday night into Tuesday morning, with the low clouds shaking out some drizzle rather than steady showers or convection. The low clouds and fog will lift by mid to late morning Tuesday.

Meanwhile, a closed upper low over southern California will weaken into an open trough by Tuesday morning, while a stalled out subtropical ridge over Texas blocks its progression. This will cause the upper level pattern to amplify, with SW flow aloft backing slightly and pulling up deep subtropical moisture up the Sierra Madres and into southern New Mexico. That's the second piece of the puzzle.

The third piece will be a strong subtropical jet over southern Baja California Monday night, which will help maintain intense thunderstorms over the Sierra Madres in SW Chihuahua. A convectively-induced shortwave trough or weak closed upper low will then roll north, along with the subtropical jet and a broad region of upper level diffluence. This shortwave trough (the fourth piece of the puzzle) will help trigger stronger thunderstorms Tuesday afternoon. Enhanced mid level flow will provide 20-30 knots of 0-6km shear, enough for more organized, longer-lived thunderstorms. The broad upper divergence will persist through Tuesday night, while a trailing vort lobe associated with the shortwave trough pivots into south-central New Mexico. This upper level support will help maintain thunderstorm development through the night and into Wednesday morning.

The result will be a fairly widespread area of "decent" moderate rainfall, with the usual smaller pockets of heavy rainfall, aided by a very moist profile (highly efficient arm rain processes), and upper level steering flow that favors training. However...as the event starts coming into range, it appears there is a high potential that somewhere in this whole mess a more persistent area of training thunderstorms will develop Tuesday night into Wednesday morning, with max QPF potential exceeding 3-4 inches in a 6-12 hour period.

The backdoor cold front will stall out along the Rio Grande Tuesday afternoon, with intense moisture convergence developing along this boundary during the evening hours. The GFS shows a mid-level jet streak of around 40 knots developing ahead of the trailing vort lobe, with a concentrated area of strong theta-e advection in the 700-500 mb layer. Where this aligns with the strong low level moisture convergence along the stalled out front, is likely where the axis of heaviest precip will occur.

Recent model runs, including the 12Z and 18Z ECMWF, 00Z GFS, and 00Z RRFS, and the last few hours of the 00Z HRRR are putting this focus area right over the Mesilla Valley and El Paso Tuesday night into Wednesday morning.

However, it is important to point out the the NBM, and the 18Z GFS and ECMWF ensembles show there is significant spread in where this area could set up. For example, the NBM mean QPF is fairly useless at the moment, as it averages out QPF maxes showing up in a wide range of places. This also becomes apparent when looking at the NBM QPF max numbers, which place the potential for 3-5 inches over wide area.

The "wide area" is anywhere from the Black Range down to Luna County, east to the Tularosa Basin and western Hudspeth County. So, not the entire CWA at least! A Flood Watch has been issued for this same area, starting Tuesday afternoon (as isolated thunderstorms first fire up) into Wednesday evening. The most critical period looks to be around 3 PM Tuesday through Midday Wednesday. This could be one of those unusual situations where heavy rain is ongoing at day break, which could result in impacts to the morning commute Wednesday. (But again, the narrow band of heaviest rain could shift into more open desert to the west or less-populated areas to the east.)

After a slug of runoff passed through, the Rio Grande is back to being empty in the Mesilla and El Paso valleys, which is a bit of favorable news.

There is also a "sneaker risk" of isolated severe thunderstorms Tuesday afternoon, especially in SW New Mexico where both deep- layer and low level shear will be maximized.

Precip will likely shift east Wednesday afternoon and diminish in intensity, with dry periods likely moving into SW New Mexico and the Mesilla Valley. Additional heavy rainfall is possible on Thursday, but models have continued to trend eastward with the heaviest rainfall, and moderated the amounts. Eastern Hudspeth County, not currently in the Watch for Tue/Wed, could come into play on Thursday.

Isolated to scattered showers and storms look to linger Friday, but with sparser coverage and much lower rainfall amounts.

Next week...a complex pattern with tropical cyclones off the Baja Peninsula, but an amplifying ridge is looking like it will keep the deepest moisture well to our west, though scattered thunderstorms will still be around.

Oh, and Wednesday high temperatures may be stuck in the 70s over a good portion of the area. 12 to 18 degrees below normal.

AVIATION

(12Z TAFS) Issued at 647 AM MDT Mon Sep 21 2026

VFR conditions through the TAF period with light wind speeds AOB 10KT. No rain chances expected today. High clouds could be seen at KTCS but more southern TAF sites should expect mostly FEW-SCT100.

FIRE WEATHER

Issued at 647 AM MDT Mon Sep 21 2026

One last quiet day with hardly any storm chances anywhere before a stretch of wet days. Min RHs today will be 16-22% in the lowlands and 25-40% in the mountains. Gradual increase in min RHs Tuesday to 30-40% in the lowlands and 50-70% in the mountains but Wednesday and Thursday min RHs increase to 50-75% in the lowlands and 80-100% in the mountains. Scattered to numerous storms expected Tuesday through much of Thursday where flash flooding will be the primary concern across the area. 20 foot winds will be light today at around 5 mph but Tuesday will become slightly breezier with speeds 10-15 mph out of the southeast. Light winds persist Wednesday and into the weekend with speeds generally around 5 mph.

PRELIMINARY POINT TEMPS/POPS

El Paso 70 88 64 75 / 0 60 90 90 Sierra Blanca 64 85 60 79 / 0 30 80 70 Las Cruces 65 85 60 72 / 0 80 90 90 Alamogordo 64 86 60 75 / 0 60 80 100 Cloudcroft 48 62 46 54 / 20 80 90 90 Truth or Consequences 63 80 60 70 / 0 80 90 90 Silver City 60 77 56 69 / 10 80 80 80 Deming 65 86 60 74 / 10 70 90 80 Lordsburg 67 84 62 75 / 20 60 70 70 West El Paso Metro 71 88 64 75 / 0 70 90 90 Dell City 65 87 63 79 / 10 30 70 80 Fort Hancock 71 93 68 84 / 0 30 80 80 Loma Linda 63 81 59 71 / 0 50 90 90 Fabens 69 90 66 79 / 0 60 90 80 Santa Teresa 68 87 63 73 / 0 80 90 90 White Sands HQ 69 87 64 73 / 0 80 90 90 Jornada Range 66 85 60 71 / 0 80 90 100 Hatch 66 86 62 73 / 10 80 90 90 Columbus 70 88 65 77 / 10 80 90 80 Orogrande 66 85 61 73 / 0 60 90 90 Mayhill 53 72 52 65 / 20 80 90 100 Mescalero 53 73 51 65 / 20 80 90 90 Timberon 52 72 49 62 / 20 70 90 90 Winston 56 72 54 64 / 0 70 90 90 Hillsboro 63 79 58 70 / 0 80 90 90 Spaceport 64 82 58 71 / 0 70 90 100 Lake Roberts 55 74 53 68 / 10 80 80 80 Hurley 61 79 57 71 / 10 70 80 80 Cliff 62 82 61 76 / 10 70 70 80 Mule Creek 61 78 59 73 / 20 60 80 70 Faywood 63 79 59 69 / 10 70 80 80 Animas 67 84 63 77 / 30 70 70 70 Hachita 66 84 62 75 / 20 60 70 70 Antelope Wells 66 85 63 79 / 30 60 60 60 Cloverdale 63 80 59 76 / 30 60 60 60

EPZ WATCHES/WARNINGS/ADVISORIES

TX...Flood Watch from Tuesday afternoon through Wednesday evening for Eastern/Central El Paso County-Northern Hudspeth Highlands/Hueco Mountains-Rio Grande Valley of Eastern El Paso/Western Hudspeth Counties-Western El Paso County.

NM...Flood Watch from Tuesday afternoon through Wednesday evening for Central Grant County/Silver City Area-East Central Tularosa Basin/Alamogordo-East Slopes Sacramento Mountains Below 7500 Feet-Eastern Black Range Foothills-Northern Dona Ana County-Otero Mesa-Sacramento Mountains Above 7500 Feet- Sierra County Lakes-Southeast Tularosa Basin-Southern Dona Ana County/Mesilla Valley-Southern Gila Foothills/Mimbres Valley-Southern Gila Region Highlands/Black Range-Southwest Desert/Mimbres Basin-West Central Tularosa Basin/White Sands-West Slopes Sacramento Mountains Below 7500 Feet.