HARLINGEN — The heck with spring, let’s go straight into summer.
In Harlingen, the forecast for Wednesday is 102 degrees, which would break the record of 99 degrees set in 1961.
In Brownsville, temperatures are expected to hit 99 degrees, one degree higher than a record set in 1964.
In McAllen, the forecast is for 106 degrees, which would be one degree shy of the record the city set in 1984.
National Weather Service meteorologists at Brownsville say the unusually high temperatures forecast for Wednesday are the result of deepening lows in the Plains bringing an intense dryline into the Rio Grande Valley.
“It’s basically a boundary between moist air and dry air which typically occurs over West Texas,” NWS meteorologist Brian Miller said yesterday in explaining a dryline. “You’ve got gulf moist air that tends to work its way inland and gets to a certain point and then more or less there’s a boundary where there’s a lot drier air to the west.”
Such a weather phenomenon is pretty unusual for the Rio Grande Valley in April.
The high temps Wednesday could break records up and down the Valley, and some of those records for the date go back more than 50 years.
“It looks like what we’re going to see is southwest winds coming in and usually that’s the trigger that they come down from the mountains in Mexico and they’re downsloping. So when that happens they tend to warm up as they decrease in altitude,” Miller said.
“It’s a phenomenon you see lots of times when winds come down from the mountains,” he added. “It’s basically the air parcel is compressed and it warms up in the process.”
The scorching forecast is far above normal temperatures for the three cities at this time of year. Average temps for the date are 87 in Harlingen, 85 in Brownsville and 88 in McAllen.
Spring allegedly began on March 20, and the summer season officially begins June 21.
But April is shaping up to mirror the first three months of 2017, each of which set heat records for McAllen. In Harlingen and Brownsville, the high temperatures for the year’s first three months were among the top five warmest ever recorded, meteorologists in Brownsville say.
Wednesday’s forecast
HARLINGEN — 102 degrees
BROWNSVILLE — 99 degrees
MCALLEN — 106 degrees
Average temperature for April 26
HARLINGEN — 87 degrees
BROWNSVILLE — 85 degrees
MCALLEN — 88 degrees
All-time hottest April 26
HARLINGEN — 99 degrees, 1961
BROWNSVILLE — 98 degrees, 1964
MCALLEN — 107 degrees, 1984
Threats forecast April-June
- HEAT — Hot weather is virtually assured. The dominant weather pattern of a series of upper-level disturbances spinning off a persistent upper-level low pressure area south of Alaska into the Pacific Northwest and then diving through the Great Basin before exiting/weakening into the southern and central Plains will keep the “Valley Wind Machine” in high gear.
- RAINFALL — The last week of April is looking dry and hot. May is definitely a wild card, and whether rainfall occurs in significant amounts depends on whether a diving western U.S. trough can get far enough south to pick up sufficient moisture from the tropics. Flooding rain or severe thunderstorms have affected the Valley and ranchlands in May 2015 and May 2016, so a similar weather phase could occur again between mid-May and mid-June.
- FIRES — Wildfire weather was eliminated by late February’s green-up following the unusual early-year rains. But Deep South Texas’ fuels can quickly dry out in late spring, especially during hot trends with occasional dry “spikes” where temperatures surge to 100 degrees and humidity falls below 20 percent. A prolonged period of dryness continuing from late March into early May could increase the threat for rapid wildfire spread.
- DROUGHT — Like the wildfire threat, early-season drought was eliminated in the Valley by early rain. But like wildfire concerns, drought also has the potential to resurrect itself quickly, especially if no rain falls and several days of “dry” heat — humidity below 25 percent — occur.
