Graphic showing wide variety of weather across Texas, March 27, 2009
From Blizzard to Blowtorch
Texas’ Freaky Friday, March 27, 2009

Early Spring in Texas often features weather extremes, a factor of the state’s location between the semi tropical Gulf of Mexico, the mountains of northeast Mexico, the Great Plains, and the Mississippi Valley. A variety of weather conditions can result, ranging from Panhandle snows to southeast Texas hailstorms. March 27th, 2009, truly defined Texas weather extremes. In the Panhandle, not only did it snow, but a bona fide blizzard occurred, with a combination of frigid temperatures hovering near 20°F, sustained winds between 25 and 35 mph gusting near 50 mph, and heavy falling snow creating near whiteout conditions. When all was said and done, measured and estimated snowfall ranged to a foot or more, with drifts in some areas exceeding 12 feet! For a summary of the March 27th Panhandle Blizzard, click here.

While a blizzard raged in the panhandle, severe thunderstorms, producing hail in excess of 2 inches, a few tornadoes, and damaging wind gusts, plowed across southeast Texas toward the upper Texas coast, in very unstable air ahead of a dryline and southeast of developing low pressure moving across northeast Texas. Farther west, behind the dryline and ahead of the front, northwest winds gusted in excess of 40 mph in spots as humidity fell to critical values, increasing the threat for explosive wildfire growth and spread. For the Rio Grande Valley, temperatures soared above 100°F as gusty northwest winds compressed the air flowing from higher terrain toward the coast, heating the surface toward daily records.

Meteorology
A developing upper level disturbance, diving south from the front range of the Rockies into New Mexico, then shifting east through North Texas (below), brought unseasonably cold air behind it. The disturbance strengthened a trough of surface low pressure in Texas, increasing the contrast between warm, humid air flowing ahead of it and much drier, and eventually cooler, air dropping in behind it. Deep Gulf moisture drawn into the system contributed to not only severe weather, but torrential rains and flash flooding across the northern Gulf region of Mississippi and Alabama. This same moisture wrapped into the storm system, creating the unusually heavy snowfall in the Panhandle. Increasing west to northwest flow behind the system brought much drier conditions to west and central Texas; initially heating up substantially between the dryline and the front itself.

RGV High temperatures (column 2), previous record/year (columns 3 and 4), and new record (yes or no, column 5).
City
High
Pvs Rec
Year
New?
McAllen/Miller
102
105*
1984
N*
McAllen/Co-op
101
104*
1984
N*
Brownsville
101
106
1984
N
Harlingen
101
104*
1984
N*
Port Isabel/Camco
101
-
-
-
La Joya
101
n/a
n/a
n/a
Raymondville
101
104*
1984
N*
Armstrong
100
-
-
-
Harlingen/Co-op
99
104*
1984
N*
Rio Grande City
99
103*
n/a
N*
Sarita 7E
99
87**
n/a
I
San Manuel
98
-
-
-
Port Isabel/Co-op
98
100*
1984
N*
Port Mansfield
97
101*
1984
N*
Falfurrias
96
103
n/a
N
Falcon Dam
95
105
1984
N
Hebbronville
94
102
n/a
N*
* Record recalulated for calendar day.
** Data incomplete.

Effect on the Rio Grande Valley
A warm, humid start to March 27th was quickly overcome by sunny, hot and dry conditions, as winds shifted to the northwest and increased to 20 to 25 mph, with a few gusts approaching 35 mph during the afternoon. Temperatures rose from 88°F to 98°F at McAllen/Miller International Airport by 1 PM, as humidity plummeted through the 20 percent level. By mid afternoon, temperatures ranged from the mid and upper 90s across Deep South Texas, to a little over 100°F across the entire Lower Rio Grande Valley, except at the beach. Humidity fell below 10 percent in some spots. Fortunately, no wildfires of significance were reported; with increasingly dry grass and rangeland, the combination of hot and very dry conditions were a recipe for rapid to explosive growth.

A warm and slightly breezy evening was followed by an hour or so of windy weather, generally between 10 PM and 1 AM, when the actual cool front slammed through. North winds 25 to near 30 mph with gusts of 40 mph or higher in some spots accompanied the front, along with a band of clouds and some sprinkles. Marine conditions deteriorated immediately, with frequent gale force gusts and seas briefly building over 12 feet very early on the 28th. Conditions gradually improved after sunrise, and by afternoon on the 28th, chamber of commerce weather had returned.

500 millibar chart, plus annotations, for weather conditions at 12 UTC, March 27, 2009
Weather Topics:
Current Hazards |  Current Conditions |  Radar |  Satellite |  Climate |  Safety

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