April showers bring May Flowers? Obs, disco for April 2012

[mappy]

Was walking the dog at 540am, just getting ready to step out into the rain with the umbrella when the entire sky went white..... dog and I both jumped at the very loud thunder that quickly followed. Holy moly.

[H2O]

No T&L here but mod rains with this quick moving line of showers

[Kevin Shaw]

A

pril 2012 Station Highlights - Gaithersburg 2 WNW Maryland by Kevin Shaw, Observer in charge

April was actually a little cooler in some respects than our record-breaking March was. Also it was statistically cooler than normal by

0.8° on the average maximum temperature (65.4°). The mean temperature of 54.4°, however, was 0.4° above normal due to the

average minimum temperature of 43.4° being 1.6° above normal. Only had 2 days of 80 or above, as opposed to 3 such days in March.

No days in April had minimums of 32 or less, as what appears to be the last 32 or lower min this spring was recorded on 3/27. On only

one other April, in 2010, did I have an above freezing lowest monthly minimum temperature. There were precious few temperature

records set this April. The only ones set were 2 daily low maximum temperature records of 46 on the 23rd and 53 on the 28th. No

precipitation records were set. The 1.92" monthly total (-1.74”) was the third driest April of all time, only surpassed by 0.49" in 1985

and 1.70" in 1997. Nine days of measurable precipitation during the month was just a bit below the normal amount of 11. No snow fell

at my station but a few flakes and some graupel fell in parts of Montgomery County on the 11th. In 34 Aprils since 1979 I have now

had 14 of them with no snow, and 12 more with a Trace. All in all though a more normal month than March, but the dry conditions

continue - only 8.30" of rain through the end of April, in contrast to the normal 13.68" total through 4/30.

The total snowfall for April was 0.0" (though we came close on April 11 with some flakes and/or graupel elsewhere in Montgomery

County). The total for the 2011-2012 season of 5.0" has set an all-time record low amount, surpassing the meager totals of 5.5" in

2001-2002 and 5.9" in 1997-1998. Theoretically we could still get snow in May, but the way it is going, that is highly unlikely.

The distribution of 17 clear, 7 partly cloudy and 6 cloudy days led to the generally dry month. Unlike March, we had only 3 days with

fog and no thunder days. While I did not hit a freezing minimum temperature during the month, I did have 12 days with minimum

temps in the 30s, which is significant, and kept soil moisture at reasonable levels along with the fairly well distributed 9 days of

measurable rainfall, though most (over 93%) of the month’s rain occurred from April 18 on to the end of the month.

My meager peak wind gust (PWG) for the month topped off at 23 MPH on the 9th from the SW. I only had 6 days with a PWG of 20

or greater, all occurring between April 1 and April 17. Conversely I had 4 days with a PWG of under 10 MPH, all occurring from April

18 on to the end of the month.

The pressure extremes occurred within about a week of each other - towards the end of the month, when most of the month’s rain

fell. Near the end of our biggest rain event of the month, I recorded a low reading of 29.37" on the 23rd then climbed slowly till the

last few days of the month, when I topped out at a modest 30.34" on the 30th.

There were 331 heating degree days and 13 cooling degree days, very similar numbers when compared with March.

The diurnal range average was just about normal (22.1° vs. 22.4°) with a max range of 36.6° on the 3rd, when we started a warm up

after the coldest reading of the month on that morning. The minimum range of 6.3° was reached on the 18th during a cloudy, cool, full

day of light rain, drizzle, and fog. April 2012 had its share of wide ranges and small ranges, with 4 days of 30° or greater ranges and

conversely, 3 days with less than 10° ranges, exactly the same numbers as I had one year ago in April 2011.

The total number of foggy days was a bit below normal at 3 but particularly noticeably absent was a total lack of thunder days at

0. The maxima temperature distribution included: 2 days in the 80s, 7 days in the 70s, 14 days in the 60s, 6 days in the 50s and 1

day in the 40s. Minima were distributed in this fashion: 12 days in the 30s, 11 days in the 40s, and 7 days in the 50s.

In summary, at least April slowed the record-breaking warm pattern that 2012 had been under so far through March. Amazingly,

global patterns were below normal temps in March and well above normal in April, reversing our local trend. I only hope that a wetter,

cooler pattern will take over for the upcoming summer to keep the records in check at least temporarily. We may not be able to hold

out much longer the way things have been going in general over the past few years.