A NO CHANGE ZONE (5/27/2011)


If you like hot, wind, muggy conditions, then you’re in luck if you live in South Texas.  As summer approaches, a transition occurs in the upper-levels of the atmosphere.  The jet stream shifts more towards the north and a sub-tropical jet stream settles in for much of the south, including deep south Texas.


An upper-level high over the eastern Pacific, off the coast of Mexico, is causing the shift in the jet stream to move a little bit north, into the central Plains.  This high is causing our winds at 500 mb out of the northwest.  Winds from this direction aloft indicate drier air, with no moisture support for rain in the upcoming future.  This also means any upper level troughs or lows will be forced to lift north, with this dominate high in place.

At the surface, a stationary frontal boundary in central Texas yesterday is now moving back north as a warm front.  This warm front is connected to the same front that brought severe weather for much of the Souther Plains, Central Plains, Midwest, and Northeastern regions over the past few days.  Because the Valley won’t see this front push through, persistent southeasterly winds and humidity will prevail over our area for the upcoming days  to come.  Below shows a 24-hour animation of radar and surface fronts from the Hydrometeorological Prediction Center (HPC): *CLICK ON IMAGE TO ANIMATE*

Figure1. National radar loop and surface fronts over the past 24 hours (21Z 5/26 - 18Z 5/27)

…Short Term & Long Term Forecast…

Mid and upper-level high will dominate over our area for the next 5 to 10 days, diverting all troughs and lows towards the central and northern Plains.  This will make our atmosphere very stable, with very little or no chance of rain for the next 3 days.   Surface low pressure over Oklahoma/north Texas and a surface high pressure over the southeastern United States will tighten up the pressure gradient for the Rio Grande Valley.  These southeasterly winds will be quite gusty at times, especially during the day.  With low level moisture in tact,  evenings will be mostly cloudy to overcast and muggy as temperatures will reach their dewpoint temperatures in the lower levels.  The winds will begin to settle down a bit by the middle of next week, as high pressure from the Rockies slides east, to overcome the high pressure over the Atlantic.  This will also bring a shift of wind direction, from the southeast to the east.  No relief in sight as far as temperatures go.  Afternoon highs will be in the mid-to-upper 90s for much of the middle and upper Valley in the short-term forecast.  However, once winds shift out of the east for the middle of next week, it will bring slightly cooler temperatures for the Rio Grande Valley.

Edinburg 3-day Forecast:

Figure 2. Edinburg's 3-Day Forecast. Issued 5/27/2011


About Brian

University of Oklahoma graduate with a degree in Meteorology. Follow me on Twitter: @WeatherInformer
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