National Weather Service rainfall forecast through Tuesday morning. (

After 22 straight days without a drop of rain, the Washington region is in need. Enter Tropical Storm Nate — which could quench the thirst of our parched lawns and gardens.

Moisture surging north ahead of Nate should arrive Sunday, which could turn showery — particularly during the second half of the day. Into Monday, the rain may become heavy for a time.

All told, about 1 to 2 inches of rain is likely, partly making up for the water deficit over the past three weeks.

Rainfall timing

GFS model simulation of rain Sunday through Monday.

Saturday, during the day and evening hours, should be dry. Shower chances are expected to commence before dawn Sunday, starting at around 30 percent.

During the day Sunday, on-and-off showers, with some possible heavy bursts, will cycle through the region from south to north. It’s not necessarily a washout, but the rain could disrupt some outdoor plans. Showers are likely to be more numerous in the afternoon than the morning, but be prepared for rain if you’re running the Army Ten-Miler.

The core of Nate’s remnants should zip through the region late Sunday night into Monday, when the rain could become very heavy. If this timing holds, Monday morning’s commute could be a slow one.

By Monday afternoon or evening, the rain should taper off as the remnants pull off to the northeast.

This timing could shift a little, and we will refine the forecast through the weekend. The above GFS model simulation brings the rain through faster than does the European model, which suggests that the rain may start later on Sunday and end later on Monday.

Rainfall amounts

The heaviest rainfall totals are likely to be west of Interstate 95 toward the mountains — closest to where the core of Nate’s remnants are most likely to pass. Also, mountains tend to intensify rainfall.

The National Weather Service rainfall forecast (see top map in this post) calls for about 1.5 inches of rain in the immediate metro region, which seems reasonable. Amounts increase to around 2 inches in the mountains but decrease to about an inch in areas southeast of Washington, the area most distant from Nate’s remnants.

Below are rain total forecasts from the American and European models:

American (GFS) model (1.5-2.5 inches in D.C. region)

European model (o.5-2.0 inches in D.C. region)

Rainfall forecast by European model through Tuesday morning. (

Wind and thunderstorm potential

We don’t expect thunderstorms or strong winds Sunday, just a chance of intermittent showers. The chance for thunderstorms and gusty winds rises Monday as Nate’s remnants makes their closest approach. Depending on their track and the timing, we could see some wind gusts over 30 mph associated with what’s left of Nate’s core.

If Nate tracks to our west Monday and the sun pops out and the atmosphere heats up, some thunderstorms could develop and cycle through the area. Anytime you have thunderstorms developing with a remnant tropical system, which has some spin associated with it, you need to monitor the potential for brief tornadoes. This is worth watching, but at the moment, we see it as a low risk.