The temperature forecast

Warmer-than-normal temperatures are favored, but not at the very strong level that dominated March thanks to the chilly weather forecast early this month. We’ll aim for an average temperature of 57 to 60 degrees compared to the normal of 56.8 degrees (last year’s average temperature was 59.4 degrees).

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The rain forecast

While we had several wet periods in March and we’re not in any sort of drought, precipitation fell well shy of average. Our models suggest similar challenges in achieving substantial rain in April. So we’ll favor 2.5 to 3 inches compared to the normal is 3.06 inches (last year, D.C. received 3.41 inches).

Historically, April rainfall has varied quite a bit from year to year. Below, see the totals since 2000:

The snow forecast

We can still get snow in April. The normal amount is a trace and we have achieved a trace four times since 2000. The only measurable snow we’ve experienced since 2000 was the 0.4 inches that occurred in 2007.

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With some of the shots of cold air over the next two weeks, a few flakes aren’t out of the question, but I’d be surprised if we got a trace or more. I’ll say below normal snow for April, which is none.

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April forecast rationale

El Niño effects lingering

While the El Niño is definitely weakening in the Tropical Pacific, it is still more than sufficient to influence our weather. The current status is straddling moderate and strong intensity.

Atmospheric effects from this feature should come in two forms for April: (1) bursts of warming from the west and (2) variable weather conditions rather than solid sustained cooling or warmth.

The undercutting Pacific flow should also keep moisture flowing into the West Coast to give California more chances of coastal rain and mountain snow in the month ahead.

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Long-range models

The National Weather Service CFS model shows a warm and dry focus for the second half of April. Like last month, we don’t expect a solid warm pattern, but that the warmer periods outweigh the cooler ones overall.

Here are the latest maps for just the second half of the month.

National Weather Service

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The National Weather Service does not make any forecast commitments for our area. Its latest call shows equal chances (EC) for both temperature and precipitation — which means equal chances for both above/below/normal conditions.

I agree that this pattern is a bit tricky as just one heavier rain event could pop us above normal. And warmth later in the month could under-perform expectations. You can read the Weather Service’s April forecast discussion here.

March forecast review

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The temperature forecast

I wrote: “Warmer-than-normal temperatures look very likely, but the big question is how warm? An average temperature of 49 to 51 degrees is favored at this time. The 30-year normal in D.C. is 46.8 degrees, so our forecast translates to temperatures 2 to 4 degrees warmer than normal. If we’re wrong, we think chances are it could even be warmer.”

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Reality: And it was warmer. The average temperature estimate of 53.5 degrees was 6.7 degrees warmer than normal. It was warmer than expected, but at least we were (a) directionally correct and (b) warned about warmer risks.

The rain forecast

I wrote: “We favor above normal precipitation for March. Normal is 3.48 inches, and we predict between 3.75 and 4.25 inches. History shows El Niño March periods, like this one, tend wet (1998 — the last big El Niñ0 — delivered 5.4 inches) and we wouldn’t be surprised if rainfall exceeds our forecast.”

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Reality: This prediction failed. We only picked up a measly 1.16 inches, which was 2.3 inches below normal. D.C. reported rain on 18 of 31 days — which seems sort of wet — but the total amounts were never very impressive.

The snow forecast

I wrote: “Below-normal March snow is favored. The normal is only 1.3 inches so if Friday’s storm takes a colder track, we’ll easily flip to an above-normal March. Right now, the setup does not look ideal for significant snow (high pressure that supplies the cold is not in the right spot). After Friday, the balance of the month looks too warm for snow and we may end up with zero inches.”

Reality: We picked up 0.3 inches on March 4, which leaves the month 1 inch below normal. Below normal was the correct call.

Summary review

Two of three forecasts were in the correct direction.

Grade: B-

