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Monday, February 11, 2013

Over-running Rain

By Gene Norman
Follow @genenormanwx on twitter

It's b-a-a-c-k...the weather pattern known as "over-running", which plagued us at the beginning of January.  The encore performance is making for a dismal start to the week, but if you can hold on for a few days - you will see the sun - eventually.  Tonight an tomorrow, however, will be dreary, damp and cool.  The recipe is simple: northeast winds at the surface keep temperatures cool while milder air aloft streams in from the southwest.  This map shows the surface winds as thin lines with arrows overlaid on surface temperatures:

Below is the depiction of the wind flow at 18,000 feet:

Periodic impulses in that flow allow showers and a few rumbles of thunder to move across Southeast Texas.  This morning, it was cold enough aloft to allow for ice pellets to reach the ground.  There were quite a few reports of brief pea-sized hail.  It's not out of the question that a few thunderstorms may allow for a repeat late tonight and early Tuesday.

This pattern should break down by early Wednesday as the upper-level winds all shift to the northwest.  That will allow cooler air to arrive in time for Valentine's Day.  A stronger push of cold air arrives during NBA All-Star weekend, so get your stylish winter wear ready!

TONIGHT: Cloudy, cool with occasional periods of light rain. Thunderstorms possible toward early morning.  Temperatures holding in the low to mid 50s. Northeast wind 5-10 mph.

TUESDAY: Showers and thunderstorms through mid-afternoon.  Rain tapering off by late afternoon, but skies remaining mostly cloudy.  Turning colder during the late evening.  Daytime highs in the mid to upper 60s, then falling through the 50s during the evening.  Northeast winds early 5-10 mph become east 10-15 by late afternoon then west-northwest by evening 15-20 mph.  

WEDNESDAY: Early clouds quickly give way to sunshine.  Remaining cool and breezy.  Temperatures in the morning start in the upper 40s, rising to the low 60s.  Steady northwest winds 15-20 mph.

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