Thursday, November 12, 2009

Warm, Windy and Wet

Another weekend approaches and my thoughts turn to the weather that I'll need to deal with if N631S and I are going to make the flight down to the DC area. At this time of year the first thing I look at is where the freezing level is forecast to be. Here the news is good:

The expected freezing levels are well above my usual IFR altitude of 8000 feet MSL, so whatever else I may be concerned with, icing should not be a factor.

Next, let's look at the "big picture":

The cyclonic flow around that low pressure center off of Cape Hatteras has been pumping wet maritime air into the Mid-Atlantic region for a while now, and the map shows an area of drizzle, showers and rain affecting the area of interest - eastern PA, MD, DC and VA. It'll be a warm flight, but a wet one.

The low is fairly deep and the isobars surrounding it are a bit crowded. This will give me brisk winds both aloft and on the surface from the northeast. In fact, FltPlan.Com is telling me to expect a time en route of under two hours and an average tailwind of 15 knots. Wheee!

It's too early to get pertinent Terminal Area Forecasts (TAF's) for airports near home at time of arrival (namely DCA and Andrews), but the TAF's for the big airports now go out 30 hours, so I can look at BWI and Dulles. Through 00Z on the 14th, they don't look too bad:

KBWI 121734Z 1218/1324 04015G25KT 6SM -RA SCT020 OVC030 
     FM122200 03017G27KT 6SM -RA BKN015 OVC020 
     FM130600 02016G23KT 5SM -RA BR OVC012 
     FM131300 36015G25KT 4SM -RA BKN012 OVC020
KIAD 121734Z 1218/1324 02013G19KT 6SM -RA SCT020 OVC025 
     FM130100 01014G24KT 5SM -RA BKN015 OVC025 
     FM131300 01013G24KT 5SM -RA OVC012

For Baltimore, four miles visibility in light rain with broken clouds at 1200 feet and an overcast at 2000. For Dulles, 5 miles visibility in light rain, and overcast at 1200. If conditions at KVKX are nearly that good, the GPS approach to runway 6 will work out just fine. The things I will need to watch as flight time draws nearer are the ceiling and visibility forecasts for KDCA and KADW. If they are much lower, I could find myself needing to divert to the ILS at Manassas.

And then there's the wind. Both Baltimore and Dulles anticipate winds from the north at about 15 knots with gusts to 25. The winds at KVKX, sheltered in the valley, ought to be a bit less vigorous, but that's manageable in any case.

A warm, windy and wet flight. Final decisions will await tomorrow's data.

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