…Tonight and Sunday..
500mb low currently over the NM/Mexico border will lift northeast tonight and tomorrow. Until then, cloudy skies and light rain will persist across the Valley through tonight and possibly into tomorrow morning. The cold front that pushed through the Valley on Friday caused a coastal trough to form just offshore. It will start to move northwest as a warm front tonight, also enhancing shower chances. However, most of the measurable, significant rain will remain to the north of the Rio Grande Valley. As the 500mb low moves northeast, it will cause the warm front to move southeast as a cold front, again, as early as late tonight. This cold front will not affect temperatures, but will generate clouds and light showers. The front will likely stall over the Valley and dissipate by Monday afternoon.
In summary, tonight will be cool and cloudy with a slight chance of a shower or thunderstorm. Low temperatures will be in the lower to middle 50s. Any rain that accumulates will be less than 1/10 of an inch. Sunday will start off cool and cloudy, but will warm up during the afternoon hours. Light rain is still possible through noon, but skies will turn partly cloudy by afternoon. Afternoon high temperatures will range from the lower 80s in the upper-Valley to the lower to middle 70s in the lower-Valley.
…Monday through Friday…
Warm temperatures are in store this week. Winds will shift out of the southeast beginning Sunday afternoon and will not be changing direction much any time soon. That means there are no cold fronts in sight. This also means that dewpoint temperatures and humidity will be in full swing for spring break. Computer forecast models are in agreement that clouds will persist this week. With southwest flow aloft and muggy dewpoints, I cannot rule out a shower or two each day. As far as temperatures go, Monday through Wednesday look to be the warmest days of the week. Temperatures will range from middle to upper 80s in the upper Valley to lower 80s in the lower Valley. South Padre Island will be the cool spot during the day, with temperatures in the 70s. Beginning Thursday, models are hinting at a more zonal and even a northwest flow aloft. If this is the case, temperatures at the surface will be slightly cooler (on the order of 5 degrees) than Monday-Wednesday. This flow may also clear the mid-level clouds, but I still believe there will be some lower level clouds. Models are then hinting at a mid-level trough sweeping through by the end of this week or beginning of next weekend. This will increase shower chances, slightly.
In summary, this week looks to be very persistent, with a slight chance of a shower each day. Monday will be warm under partly sunny to mostly cloudy skies. Winds will begin to pick up again Monday afternoon. On Tuesday, expect warm and windy conditions with temperatures near 90 west of highway 281. Winds don’t slow down much on Wednesday. Temperatures will be warm again, ranging from middle 70s at the island to upper 80s in the upper-Valley. Thursday will be another breezy day under partly sunny/cloudy skies. High temperatures will be in the middle 80s in the upper Valley, and upper 70s in the lower Valley. Friday will be mostly cloudy with a chance of a shower or thunderstorm in the afternoon. Highs will still be in the middle 80s in the upper Valley to upper 70s near the coast.