Grants, NM 87020 Weather

Key Messages

Issued at 1121 AM MDT Wed Oct 21 2026

- Flash flood risk increases in northwest New Mexico today, spreading eastward into central New Mexico late Thursday into Friday. There is the potential for more heavy rainfall and flash flooding in eastern New Mexico over the weekend.

- A few strong to severe storms in western New Mexico today could produce damaging outflow wind gusts and large hail. The severe threat extends into central New Mexico Thursday, then into eastern New Mexico Friday.

- Rainfall over northwest New Mexico this week will create rises on tributaries as well as main stem rivers such as the San Juan and Animas. No river flooding is currently forecast, but trends will be monitored closely over the next few days.

Short Term

(Today through Thursday) Issued at 144 AM MDT Wed Oct 21 2026

The Pacific storm system that will impact the desert southwest mid- week through the weekend is starting to take shape. A closed Low is spinning off the coast of soCal while an atmospheric river (AR) extends from the central Pacific into Arizona. A seasonably moist airmass already resides over New Mexico, with dewpoints ranging from the 30s in the northeast to the upper-50s in southern New Mexico. Very strong moisture advection will occur today in central AZ, with western New Mexico along the eastern fringes. PWATs surge to 200 to 350% of normal over northwest NM, shattering record atmospheric moisture levels for mid-October. Rain chances will favor the northwest corner of the state Wednesday, although they have continued to trend lower given that the closed Low off the California coast should take its time moving inland. The path of the main closed Low has continued to trend further northwest and is therefore more progressive as it gets picked up quicker by the polar jet stream.

Both the severe and flash flood threat Wednesday will focus over the NW corner of the state. Both the HREF and RRFS show bulk shear of 30 to 40 knots along with sfc based CAPE of around 500 J/kg overlapping in northwest NM, which may be sufficient to support the development of a few supercells. Furthermore 0-1 km SRH values of 100 to 150 m2/s2 suggest a low potential for a brief tornado in far west NM near the AZ border. In fact, SRH values trend higher (up to 250) during the evening and overnight hours, although the lack of sfc based CAPE will be the limiting factor for nocturnal supercells.

Hi-res models are bearish on the potential for heavy rainfall through Thursday morning, showing a less than 20% chance of 1" in a period of 6 hours or shorter. This looks to change on Thursday as the main IVT plume finally moves into far western NM and the main trough lifts into the central Rockies. An area of focused convection is likely to push from eastern AZ into western NM Thursday where 6- hourly LPMM rainfall amounts from the HREF show the potential for localized rainfall totals of 1-3" with this main band. This band will become decoupled from the upper-level forcing as it crosses the Continental Divide, rapidly dissipating as it attempt to move into the Rio Grande Valley. The marginal severe threat Thursday afternoon will focus along and just ahead of this precip. band.

Long Term

(Thursday night through Tuesday) Issued at 144 AM MDT Wed Oct 21 2026

While the main trough will eject northwest into the northern Rockies Thursday into Friday, troughing associated with the sub-tropical jet will persist over the desert southwest Friday into the weekend, keeping moist southwest flow over New Mexico. The main area of diffluence aloft will focus over eastern NM on Friday afternoon. A swath of MU CAPE of 500-700 J/kg will likely extend from south- central NM into the northeast corner of the state. Training of storms could produce some localized flash flooding and the Marginal ERO has been maintained with very little change. Given that elevated instability will be driving much of this convection, high rain chances will continue into the overnight hours.

This second storm system will be more neutrally titled, allowing stronger southeasterly moisture advection into eastern NM over the weekend. Upslope flow along with strong diffluence aloft will drive precipitation, but persistent low clouds could impact sfc based instability. 48-hour rainfall totals continue to trend higher, with 50th percentile amounts now showing a swath of 2-3" in the east- central and northeast plains. High-end guidance (90th percentile) shows values upwards of 4.5" for the same period. Drier westerly flow should eventually take over Monday or Tuesday of next week, with only lingering PoPs across southeast New Mexico.

Aviation

(18Z TAFS) Issued at 1121 AM MDT Wed Oct 21 2026

VFR conditions prevail and are forecast to persist across central and eastern NM, although with the development and gradual lowering of VFR cigs. Sct/num showers and thunderstorms will bring MVFR impacts off-and-on through the period across far western NM. Thunderstorm impacts are likely late this afternoon and evening at KGUP and KFMN.