Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Brownsville Texas
638 PM CDT Thursday Jul 24 2014
Discussion...updated for latest aviation discussion below.
Aviation...VFR conditions expected for the next 24 hours as
surface high pressure prevails across the Gulf of Mexico.
However...a brief period of MVFR conditions possible at taf sites
around sunrise but confidence remains low...so will not mention
for this taf cycle. Moderate winds now will slowly diminish
through this evening and become light overnight. Southeast to
south winds will increase to moderate levels by late Friday
morning through the afternoon hours.
Previous discussion... /issued 137 PM CDT Thursday Jul 24 2014/
Short term /now through Friday night/...westward-moving seabreeze
boundary is now progressing through the immediate coastal
counties... with short-lived isolated convection firing along the
boundary over Kenedy County. Larger and longer-lived convection is
noted offshore between 20 and 60 nautical miles.
Rest of today...high temperatures were increased across the bro County warning forecast area
by 1 degree based on trends over the past several days and current
observed temperatures. Isolated convection was extended all the way
to Zapata County due to steadily increasing cumulus field within all
off deep south Texas and the Rio Grande Valley.
Tonight...overnight low temperatures appeared reasonable and were
left intact. Think very isolated streamer shower activity will
affect the adjacent Gulf of Mexico waters...so included this in the
Friday...even with broad 500 mb high pressure centered over the New
Mexico/Texas area and extended over the bro County warning forecast area...500 mb weakness/
troughiness will exist along the coastline of Texas. Precipitable
water values will be close to 2 inches...and when combined with
daytime heating...should result in another round of isolated showers
and thunderstorms. Once again opted to increase high temperatures by
1 degree across the entire region.
Friday night...a Carbon copy of Thursday night...with isolated
streamer showers offshore and temperatures roughly near normal.
Long term...upper ridge centered over Texas on Saturday and the
pesky weak upper level low has dissipated just offshore. Beginning
Sunday...the upper ridge slowly retrogrades amend amplifies across
the western third of the US. This will allow for a deep trough to
envelope the eastern two thirds of the nation as we move into middle
week. This will also drive a cold front into Texas...but this
feature will not directly impact the rgv and deep south Texas.
The upper ridge will continue to dominate the rgv and much of SW
Texas throughout the extended periods. In fact...temperatures will
likely edge upwards a tad Wednesday and Thursday as the orientation of the
ridge shifts to either directly overhead or nearly overhead
allowing for a weak northerly flow. Either of these will result in
drier middle levels and in an area of stronger subsidence where typically
the hotter temperatures occur. Conversely...on Saturday...the ridge
orientation places the rgv on the southern edge which allows for a
more moist weak easterly flow. So...not only will maximum temperatures likely
edge upwards...but so will the heat index. There is the potential
that heat indicies could top 110 in some areas by Thursday. Precipitation
chances appear slim to none through the extended.
Marine...now through Friday night...buoy 42020 reported calm winds
with seas of 1 foot with a period of 8 seconds at 13 CDT/18 UTC.
Surface high pressure will provided fine marine conditions for the
Lower Texas coastal waters through the period. Small craft exercise
caution and Small Craft Advisory are not expected to be needed.
Saturday through Tuesday...overall favorable marine conditions
anticipated with the daily ritual of 15 knot southeast winds
during the afternoon and early evening hours. Seas not impacted
and should remain at or below three feet. Chances for rain look
This product is also available on the web at: