Is there any weather risk to your plans?

Sep 13, 2026

You're planning a 7am flight tomorrow. It rained all day today and only stopped at dusk. The METAR now is 00000KT 10SM CLR 14/13 A3020. Tomorrow's TAF, valid through your departure: VRB03KT P6SM FEW250. Winds aloft at 3000', 270 at 10 knots. Is there any weather risk to your plans?

AMore rain from low pressure

Fair instinct after a full day of rain. But the rain has already cleared, the sky is CLR, and the altimeter is 30.20 and rising, which is high pressure moving in behind the front. The next weather isn't rain, it's what a clear calm night does to wet ground. Option B is the answer.

Read the full explanation

BFog at the field

That's it. Wet ground from the rain, clear sky, calm wind, and a 1 degree temp/dew point spread: every ingredient for radiation fog, and a 7am departure lands right at the coolest part of the morning. The TAF didn't forecast it, and that's the lesson.

Read the full explanation

CWind shear from the inversion

You're right that a calm surface under a nighttime inversion is a low-level wind shear setup, but it needs a low-level jet above it. Winds aloft at 3,000 are 270 at 10, so there's nothing to shear against. Option B is the answer.

Read the full explanation

DNothing, the TAF calls for VFR

The TAF says VFR, and that's exactly the trap. A TAF is a forecast for the airport, not a guarantee, and fog is one of the things forecasters miss most often. Wet ground, clear sky, calm wind, and a 1 degree spread say fog whether the TAF mentions it or not. Option B is the answer.

Read the full explanation

Pick an answer. You can try as many as you like.

Read the full explanation

The explanation

B. Fog at the field

Every ingredient for radiation fog

Radiation fog forms when the ground cools by radiation on a clear, calm night and chills the air above it to the dew point. Here everything lines up:

The ground is soaked from a full day of rain.
The sky is clear, so the heat radiates away.
The wind is calm, so the cool air stays put.
The temperature/dew point spread is already down to 1 degree, with hours of cooling still to go.

A 7am departure sits right around sunrise, the coolest part of the morning, which is peak fog.

The TAF isn't a guarantee

The TAF calls for VFR, and that's the trap. Radiation fog is one of the harder things to forecast because it depends on very local conditions, and a TAF covers a 5 mile radius. That's why the METAR trend and the ground conditions matter as much as the forecast.

It will burn off, but not at 7

Radiation fog usually lifts a few hours after sunrise, once the sun warms the ground. That doesn't make it a non-issue for a 7am departure. It makes it a delay, which is still a risk to your plans. Check the morning METAR before you go.

Why not the other choices

The rain has already cleared, the sky is clear and the altimeter is 30.20, which is high pressure moving in behind the front. A calm surface under a nighttime inversion can set up low-level wind shear, but only with a low-level jet above it, and the winds at 3,000 feet are 270 at 10.