Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 251955

Area Forecast Discussion
National Weather Service Brownsville TX
255 PM CDT Tue Apr 25 2017

.SHORT TERM (Now through Wednesday night): High pressure over the
Gulf is interacting with a storm system over Oklahoma, keeping
stronger winds going over the area today. A low level jet is coming
in from the southwest, capping the boundary layer. Surface winds
will decrease somewhat tonight, with increasing low clouds and dew
points. Overnight low temperatures will be in the 70 to 75 degree
range. A shift of surface winds to southwest Wednesday morning with
an infrequent approach of the dryline into the CWA, coupled with a
persistent cap, will promote a heat spike, sending daytime high
temperatures to near record or record values. Look for mid 90s to
supra century mark readings for the day. Northwest winds will kick
in by around mid day, however, scouring out the inversion with
deeper, drier air, but the trend toward record high temps will
already be in motion. Went slightly above consensus for high temps,
closer to the GFS than the NAM/ECMWF. Clear and mild Wednesday
night, with low temperatures easing off a few degrees into the 60s,
while northeast winds reflect the arrival of a follow-up high press
air mass.

.LONG TERM (Thursday through Tuesday): Story for the long term
remains the heat. Mean longwave upper trough maintains southwest
flow aloft through much of the period, while a shortwave trough
digs into the mean trough Friday over the western US, shifting
east through the weekend. This shortwave sends a more significant
cold front across Texas and through the CWA by Sunday.

Behind the front, slightly cooler temperatures expected Thursday,
with highs in the 80s and 90s. Surface high pressure shifts east
during the day Thursday, with southeasterly flow returning by
Thursday afternoon. Pressure gradient begins to tighten moving
into Friday as low pressure develops over the southern plains.
Breezy southeasterly winds expected to develop on Friday,
especially across the coastal zones. Dry southwesterly flow aloft
combined with warm air advection from southerly flow at the
surface will lead to hot and dry conditions Friday and Saturday.
Plenty of sunshine expected, especially across the western zones
as moisture remains limited to below 850 mb and above 250 mb,
with plenty of sunshine expected. The combination of these
factors combined with increasing thickness values and 850 mb
temps in the 24 to 28 C, will translate to well above normal
temperatures for the CWA, with temperatures easily surpassing the
century mark across much of the inland areas west of Highway 281
Friday and spreading further east on Saturday. Nudged max temps up
a degree Friday and Saturday to reflect the current upward trend
in guidance. RH values drop below 25 percent for a few hours
Friday and Saturday afternoon across Zapata and portions of Starr
and Jim Hogg counties, but winds stay below 15 mph, so fire
weather concerns will be minimal at this point.

Ahead of the next cold front, moisture deepens slightly Saturday,
but remains limited to below 850 mb, with a deep dry layer aloft.
Given the general lack of moisture, rain chances will remain
limited with the front, and have kept pops below 15 percent.
Behind the front, cooler and dry air surges across the region,
with skies clearing. Dewpoints fall into the upper 30s and lower
40s by Sunday afternoon, dropping RH values into the 18 to 25
percent range across much of the inland areas west of Highway 281
and there may be an opportunity for some fire weather conditions
Sunday afternoon. Temperatures will be noticeably cooler Sunday
compared to the previous days, with highs only reaching into the
80s. Dry air lingers into Monday with RH values in the teens and
twenties across the western counties Monday afternoon, but winds
remain on the lighter side, possibly limiting any fire weather
concerns for the day. During the day Monday, high pressure shifts
east, allowing southeasterly flow to resume and Gulf moisture
beginning to return, with temperatures rebounding Tuesday.


.MARINE (Now through Wednesday night): Small craft advisory
conditions are in effect now through midnight...and may persist on
the Gulf slightly longer. Winds may shift to southwest Wednesday in
response to surface troughing associated with the approaching
dryline. Winds will decrease during the day at any rate with the
approach of follow-up high pressure, which will arrive Wednesday
night, shifting winds to northeast. A brief surge to small craft
advisory condition criteria will be possible Wednesday night, though
only briefly.

Thursday through Sunday: Marine conditions improve briefly Thursday
as high pressure moves overhead, allowing winds to lighten and
shift to the southeast and seas to subside through the day.
Pressure gradient tightens during the day Friday, with strong
winds and building seas expected as the next low pressure system
moves across the southern plains. Next cold front poised to push
across the lower Texas coastal waters, late Saturday night into
Sunday shifting winds to the northeast. Small craft advisory
conditions likely on the Laguna Madre Friday into Saturday morning
and once again Sunday and on the Gulf of Mexico waters out to 60
nautical miles Friday through Sunday.


.FIRE WEATHER: The main concern will be Wednesday morning to
afternoon as drier air surges into the CWA from the northwest. Upper
Valley winds at 20 feet are forecast to increase to 15 to 20 mph for
a few hours in the late morning to early afternoon, while relative
humidity values crash into the teens for most inland areas west of
US 77/I-69E. Wildfire growth and spread will be enhanced, with fire
weather parameters becoming marginally critical.


GM...Small Craft Advisory for winds until midnight CDT tonight for

     Small Craft Advisory until midnight CDT tonight for GMZ150-155-



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