Bureau of Land Management
BLM MT UAS Project Tracking & Reporting
Bureau of Land Management · Montana/Dakotas
BLM-MTDK UAS

Flight weather

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About these readings
Wind & gust
The usual limiting factor. Gust matters more than sustained wind: a multirotor corrects continuously, and a gust that exceeds the aircraft's authority costs you position hold and battery at the same time. Reported at 10 m above ground — flow at altitude is normally stronger and less sheltered than the surface reading.
Temperature / dewpoint spread
The gap between air temperature and dewpoint, which is more useful than either number alone. A spread closing toward zero means the air is saturating: fog or low stratus is forming, and visibility can collapse quickly. A small spread near or below freezing also indicates icing potential. Highlighted at 4 °F or less.
Density altitude
The altitude the air feels like to a rotor, after correcting field elevation for pressure and temperature. High density altitude thins the air, so rotors generate less thrust: climb rate drops, payload margin shrinks, and endurance falls. On a hot afternoon at these elevations it commonly runs thousands of feet above the ground you are standing on, which is the failure mode that surprises pilots trained at lower elevation. Computed for the project site, not the reporting station. Highlighted when it exceeds site elevation by 2,000 ft or more.
Ceiling & maximum altitude
Ceiling is the lowest broken or overcast layer; scattered and few layers are not ceilings. Which cloud rule applies depends on how you are operating, and the badge beside the coordinates shows which set this page is using.
COA / part 91 (default). COA 2025-WSA-16323 authorizes Class G operations at or below 1,199 ft AGL. Under 14 CFR 91.155, Class G at or below 1,200 ft AGL by day requires 1 statute mile visibility and remaining clear of clouds, so the ceiling itself becomes the cap when it falls below 1,199 ft. Night minimums are higher.
Part 107. 400 ft AGL, 3 statute miles, and 500 ft below the clouds — add rule=107 to the URL to use these instead.
Either way the COA altitude applies in Class G only, and this page does not check which airspace the site sits in. Override the ceiling with the alt parameter.
Visibility
Threshold follows the rule set in force: 1 statute mile for daytime Class G under 91.155, 3 statute miles under 107.51. Highlighted below the applicable figure.
Weather minimums inside a TFR
The COA waives 91.155 only for operations conducted within a 91.137 TFR, where the incident or on-scene commander is responsible for airspace segregation and deconfliction between manned and unmanned aircraft. Outside a TFR the standard minimums above apply, and this page always displays the unwaived thresholds.
Precipitation
Accumulation in the past hour at the reporting station. Most airframes are not rated for flight in precipitation, and water on the lens ends a mapping mission regardless of what the aircraft tolerates.
Kp index
Planetary geomagnetic activity, 0–9. Elevated Kp disturbs the ionosphere and degrades GNSS accuracy, which matters more for PPK and RTK survey work than for ordinary flight: it lengthens time to fix and can leave you with float rather than fixed solutions. Kp 5 and above is storm level and is highlighted. Below about 4 it is not worth thinking about.
Sun & lighting
Under the COA these times are a lighting trigger, not a hard stop. The Certificate of Waiver requires anti-collision lighting for civil twilight and night operations to increase the conspicuity of the aircraft, and the system must be operational at all times, day or night, unless operating in a TFR — the CoW waives 91.209(a)(1) only inside a TFR. A reminder appears here when the current time falls outside sunrise to sunset. Sun angle also drives shadow length: low-sun imagery produces long shadows and weaker tie points in photogrammetric processing. Computed from the site coordinates and today's date.
Before you fly
Not weather, but on the same checklist. The COA requires a Distant (D) NOTAM not less than 24 hours and not more than 72 hours in advance of routine operations, cancelled when the operation is complete; first responder and prescribed fire operations may file as soon as practicable. Airport standoffs are 5 NM from a towered airport, 3 NM from an airport with a published instrument procedure, 2 NM otherwise, and 2 NM from a heliport. MTR and SUA deconfliction is the operator's responsibility.
Forecast sections
Watch-outs and the day/night outlook come from the National Weather Service gridded forecast for the project coordinates. Current conditions come from the nearest station that is reporting, which may be a considerable distance and elevation away.