Monday, December 14, 2009

Ground Fog

THE FOG comes
on little cat feet.

It sits looking
over harbor and city
on silent haunches
and then moves on.

--- Carl Sandburg

The fog seems also to be fond of aerodromes. A nice layer of radiation fog was nestled across the runway when I arrived at KVKX this morning about 1210Z. According to Paul Freeman's fascinating Abandoned and Little-Known Airfields site, before KVKX was called Potomac Airfield it was Prince Georges Airpark and before that it was Rose Valley Airport. And it is in a valley. This results in pleasantly calm wind conditions much of the time, and a tendency to collect ground fog.

From midfield the trees beyond the end of Runway 6 were lost in the mist, so it seemed that visibility was less than 1/4 mile. There was naught to do but go about getting N631S ready for flight and wait for the rising sun to accomplish its thermal task.

In truth the fog wasn't a complete surprise. I'd checked the weather at about 1130Z. At that time the METAR for KDCA was encouraging:
KDCA 141052Z 19003KT 10SM SCT130 01/00 A3016
But the word from KADW was less so:
KADW 141129Z AUTO 20004KT 1SM ... BR CLR M01/M01 A3013

Still, a mile isn't bad...but it would get worse before it got better.

I took my time pre-flighting N631S while the Tanis heater warmed the engine, then started and taxied to the fuel island and topped off the tanks. By the time I'd finished fueling and checked the weather in the office again the sun was visible through the murk above the tree line, and the density of the fog seemed to be waning. The on-field weather instruments soon were claiming a mile and I could see past the end of the runway, so I called Potomac Approach for my clearance and headed out just before 14Z, about an hour later than I'd have been sans fog.

The fog was certainly thinning, but visibility was still limited - until I'd taken off and climbed to about 200 feet AGL where there was all of the blue sky and sunshine one could wish for. The balance of the trip to KBDR was uneventful, in clear VMC with a fair tailwind.

No comments: