Cold Front To Pass Through Valley Tomorrow


High/Low temperatures around the Valley today (3/4/2011):

Brownsville: 82/63
Harlingen: 81/57
McAllen: 84/63
South Padre Island: 75/66
Weslaco: 82/64
Edinburg: 85/59

Clouds stuck around for much of the day around the Valley.  This prevented high temperatures to reach the upper 80s and even lower 90s.  Pressure gradient has been getting tighter as a cold front is approaching the RGV.  This gradient is causing winds to pick up a bit.  What started off as calm winds this morning has now increased to 20+ mph, with gusts up to 30 mph.

For tonight, clouds will begin to increase from Gulf moisture and lift.  Tonight’s lows will reach the middle to upper 60s around the RGV.  Winds should begin to decrease later tonight, resulting in patchy fog developing  in some areas after midnight.

(3/5/2011): Saturday will start off with some patchy fog, but should burn off by the early morning hours.  By mid-morning, a cold front will begin entering the Valley.  This will affect afternoon high temperatures.  Showers and even isolated thunderstorms will develop along and behind the cold front.  Models are leaning toward a better chance (60%) of showers in the middle and lower Valley;  I’ll give the upper Valley a 30% chance of showers, but only an isolated chance.  Depending on the exact timing of frontal passage, high temperatures will be in the lower to middle 70s, then dropping after it passes. Clouds will linger until late Saturday night.  Winds will also be gusty from the N at 15-25 mph, with higher gusts. Saturday night lows will be a bit cooler, in the middle to upper 40s/lower 50s in the lower Valley.  Winds will be out of the N between 8-15 mph.

(3/6/2011): Sunday will be much cooler than previous days here in the RGV.  Clouds will begin to clear very early Sunday morning, becoming clear by mid-morning hours.  Humidity and dewpoint temperatures will drop after the cold front passes on Saturday.  This will make it feel nice and fresh on Sunday.  Sunny skies will allow for temperatures to reach the lower to middle 70s.  Winds will also be calmer, out of the east at 8-13 mph.  Sunday night will be mostly clear with lows in the lower to middle 50s.  Winds will be out of the east at 10-15 mph.

(3/7/2011): By Monday, winds will be out of the SE once again, increasing between 10-15 mph. A stationary front, just south of the RGV will allow for low level moisture to develop and therefore, clouds.  Afternoon highs will the in the middle to upper 70s, and even the lower 80s in the upper Valley.  Monday night, clouds will linger and temperatures will be mild, with lows in the lower to middle 60s.

Figure 1. Image courtesy of NWS-Brownsville. Saturday's conditions.


Looking at current upper-air and surface data, there is a positively tilted 500mb trough in the middle of the CONUS.  A jet streak over KS/OK/MO is causing lift and instability, resulting in severe weather at the surface in MO and IL.  This 500 mb trough will continue progressing eastward over the next 36 to 48 hours.  At 300mb, the trough is further west, over the Rocky Mtns.  Significant divergence over NW MO/W IL/SE IA is evident at this level as well.  Copious amounts of moisture advection into this area can be seen at 850mb.  Also, a pretty decent temperature gradient at 850mb is visible from W OK through NW IL.  Finally at the surface, a cold front associated with a surface low is evident from W TX northwest through NE IL.  With lower level moisture from the Gulf of Mexico, lots of precipitation in the warm sector of the surface low.

What this all means is that all of the evidence and support for precipitation in the Central Plains, Midwest, and South regions is there.  This will all be pushing eastward over the next 2 or 3 days, creating severe weather and flooding problems for the South, Northeast and Atlantic East.

Beginning Monday night/Tuesday morning, another storm system will be forming in the western US.   GFS has an impressive mid-level low forming Monday, and keeps its composition for much of next week.  This, in turn, will bring another strong surface low and more severe weather for the South and Midwest Tuesday through Friday of next week.  Timing and intensity is still questionable.


Figure 2. Current Radar and Surface fronts (8:15 pm CST 3/4/2011). Plenty of lower-level and upper-level support for heavy rain and severe weather.


About Brian

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