Date: 202112
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Medium Transport
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Ferry / Re-Positioning
Flight phase: Landing
Airspace: Class G ZZZ
ATC / advisory: UNICOM ZZZ
Reporter organization: Corporate
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Ground Event / Encounter Weather / Turbulence; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
Result: Flight Crew Took Evasive Action
Contributing factors: Airport; Weather
Primary problem: Airport

Narrative: Showed braking action to be medium (3/3/3). Dry snow.METAR showed VFR conditions. Temperature above freezing. 10 SM Visibility. Light Rain (No rain observed during pattern and landing). Winds 180 16 Gust 21 within crosswind component.Stable descent and approach. Compacted snow appeared to be on the runway edge. Stable speeds. Centerline touchdown. Speed brakes extended. Nosewheel on the runway. TR's deployed in full. Brakes applied at roughly 60. 70 kts. Right main went over what appeared to be a patch of compacted snow. Caused the aircraft to nose veer left. Rudder application was added to correct while simultaneously the left main ran over what appeared to be compacted snow. At that point the aircraft made an extreme left turn. No further rudder input was added to not exacerbate further loss of control. The aircraft then exited the left side or east side of the runway. Came to a stop roughly 20 feet from the runway edge. No crew member was hurt. No aircraft damage.With NOTAM and current METAR. Would have diverted to filed alternate of ZZZ1.


Second narrative: Approaching ZZZ on the NDB approach; we made visual contact with the field and landing runway. Based off of the conditions we observed the runway appeared to have a bit of compacted snow to the side edges however the middle was observed to be clear. We requested the Visual approach and flew it down to touchdown. Upon touchdown we landed perfectly centered as the main gear made ground contact the speed braked were extended; as the nose made ground contact the Thrust Reversers were deployed and verified to be extended. At about 60-70 kts the brakes were applied at the same time the right main gear appeared to run over compacted snow. At that point the aircraft began to veer to the left; at which corrective input was made and simultaneously the left gear appeared to run over compacted snow. At that point the aircraft veered to the left and exited the runway about 20 ft. before coming to a full stop. No one was hurt nor was the aircraft damaged.Based off of the NOTAMs and current METAR which indicated dry snow along with braking action to be 3/3/3 (Medium) and the observed visual conditions of the runway we concluded that we could perform a safe landing. However after we exited the aircraft we personally observed the runway and taxiways to be Nil.Had we known prior to landing the surface conditions of the runway and taxiways we would have flown to our filed alternate airport ZZZ1.


Synopsis: Corporate flight crew reported NOTAMs and METAR indicated favorable weather; yet snow and ice were present; resulting in loss of aircraft control and excursion from runway.