I'd been watching the weather map for several days and the synoptic picture forecast for Friday afternoon wasn't very nice. A cold front associated with a deep trough was approaching from the West and was forecast to stall along the coast on Friday. Conditions would be ripe for lots of convective activity. Thus, the Terminal Area Forecast (TAF) for Washington's National Airport (KDCA) was unsurprising:
TAF AMD KDCA 281852Z 2819/2918 19010KT 5SM TSRA BKN050CB TEMPO 2819/2820 VRB30KT 2SM +TSRA OVC030CB FM282200 25007KT P6SM VCTS BKN050CB FM290000 27005KT P6SM VCTS BKN050CB FM290100 27005KT P6SM BKN050 FM290400 VRB03KT P6SM SCT130 FM291600 21007KT P6SM BKN050=I was planning a departure at about 1930Z, so the period of heavy thundershowers (+TSRA) was expected to be over well before my arrival, but the prevailing weather for the whole evening was calling for thundershowers in the vicinity. The TAF's for intermediate locations enroute looked pretty much the same.
I decided to depart anyway, watch the weather carefully, and if necessary, land before things got boisterous and wait it out overnight if necessary. Despite the highly convective environment, this was "air-mass" weather, not frontal activity. The organized lines of storms accompanying a front defy penetration, while the more scattered weather in store in this case often offers a way through if approached with an abundance of caution, lots of information and plenty of fuel.
The controller's reply was, "Everything looks good as far as Lancaster, then there's a band of precipitation, heavy to extreme, from south of Lancaster and to the northeast about 50 miles."
I then asked, "Have you got a work-around for that band? I don't want to go and paint myself into a corner down there."
This drew a "Skylane 31 Sierra, stand by," which meant that I had him thinking about the problem. After a pause of about a minute, the controller came back to me with, "Skylane 31 Sierra, it looks like after Lancaster, Victor 143 down toward the BRINS intersection will keep you clear of the weather. Then you can go direct Baltimore." It was my turn to say, "Stand by." I grabbed the Low Altitude chart from the seat next to me, quickly flipped it open to the panel depicting Lancaster, found V143 (which departs LRP on about a 248 heading) and traced it to the Southwest, and located BRINS. I compared that with the NEXRAD depiction and then pressed the Push-to-Talk switch. "Harrisburg, 31 Sierra likes the looks of Victor 143 after Lancaster. I think that's a plan."
I turned N631S toward Baltimore, still in the clear and keeping the weather well off to our left. About 25 miles West of Baltimore, the PCT controller said, "Skylane 31 Sierra, there's some weather moving in to the South of Baltimore; that direct Nottingham route may not work. I'd suggest you tell the next controller you'll need to deviate to the East to stay clear of that weather." I acknowledged that with thanks, and got "Contact Potomac on 119.85."
The controller then said, "Go ahead and navigate around the weather to the east. Just let me know what turns you're making." I said, "31 Sierra is going to go from present position on a 160 heading for a while, then I'll go direct Nottingham when able." This drew, "31 Sierra, that's approved."
And here's a half-minute of video recorded in about the same spot:
A few miles to the south, the way was clear for a turn toward home plate and the landing at Potomac Airfield was uneventful. It took about a half-hour to get N631S put to bed in the hangar, and as I was driving off of the airfield the heavens opened and gave forth an impressive deluge, leaving me thinking that timing is everything.
All things considered, the conditions for this flight were pretty challenging. Good on-board weather awareness (i.e., NEXRAD) was a 'no-go' item but the real essentials were a creative and savvy controller at Harrisburg approach who quickly developed a workable re-route, and a couple of smart, and above all flexible controllers at PCT who made it possible for me to complete the trip safely. My profound thanks to all.