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Area Forecast Discussion (AFD)

Issued by Brownsville/Rio Grande Valley, TX (BRO)

FXUS64 KBRO 250023 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
723 PM CDT Wed May 24 2017

.DISCUSSION...Updated for latest aviation discussion below.


.AVIATION...VFR conditions will prevail through the period with
mostly clear skies expected. Winds will increase and be gusty at
times Thursday as low pressure develops in the Southern Plains.


.PREV DISCUSSION... /issued 241 PM CDT Wed May 24 2017/ 

SHORT TERM (Tonight through Thursday Night): 500mb ridge across
the central United States tonight will provide subsidence across
the state tonight into Thursday even as surface high pressure
across the Rio Grande valley moves eastward allowing an onshore
flow to return late tonight into Thurs morning. The pressure
gradient will increase across the lower Texas coast Thursday and
breezy conditions will develop across the coastal sections of the
CWA Thurs afternoon. Clear skies and light winds in combination 
with the drier air across the area will provide relatively cool 
temperatures tonight. With the onshore flow returning across the 
Rio Grande valley tonight into Thursday...temperatures will be 
near normal to slightly above normal Thurs afternoon and Thurs 
night as a result.

LONG TERM (Friday through Wednesday): On Friday, the 500 hPa pattern 
will flatten and support the lateral movement of a southern Plains 
system toward the midwest. The local area of deep south Texas and 
the RGV will remain under the influence of Gulf high pressure under 
the western limb of the Bermuda ridge. Little change will occur on 
Saturday with the dryline parked over the Big Bend area. On Sunday 
a front will push south into central Texas as 500 hPa ridging builds 
over the western United States. Intersection with the dryline will 
spark Sunday night convection over the Big Bend region, essentially 
the lower to mid Rio Grande Valley nomenclature on a national scale. 
Temperatures through Sunday will trend higher, becoming several 
degrees above normal. Look for a mix of clouds and sun through the 
weekend, moderate to breezy southeast winds and high temperatures in 
the 90s to a skosh above the century mark with low temperatures 
well into the 70s if not near 80. 

By Sunday, with a mean trough over the upper Midwest and ridging 
again building over the western United States, high pressure will 
spill southeast from the upper northwest United States, pushing into 
central Texas. Convection will develop over the RGV Plains, upstream 
from deep South Texas and the RGV. The front will approach the CWA 
on Monday, with winds weakening and shifting to east, with some 
uncertainty as to whether the front will have enough push to make it 
through. At any rate, the atmosphere will be slightly destabilized 
resulting in an increase in rain chances, particularly for the 
northwest sector of the CWA, where convection may fire late Monday 
night into Tuesday morning. Southeast flow will regain its footing 
on Tuesday, with diurnal showers over the CWA and gently pushing the 
frontal boundary back north.

MARINE (Tonight through Thursday night): Seas were near 4 feet
with north winds near 12 knots at buoy020 early this afternoon.
Winds will veer to the southeast across the coastal waters tonight
as high pressure across the Rio Grande valley and northeast Mexico
moves eastward. Light to moderate southeast winds tonight will
veer to the south to southeast Thursday and increase as the
pressure gradient increases across the western Gulf of Mexico with
low pressure across the Texas panhandle and high pressure across
the central Gulf. SCEC conditions will be likely across the
coastal waters with moderate to strong south to southeast winds 
Thursday. Winds will increase offshore the lower TX coast Thurs 
night and small craft advisories will likely be needed.

Friday through Monday night: Persistent high pressure over the Gulf 
will combine with equally persistent lower pressure over the 
southern High plains to produce moderate to fresh or low end strong 
southeast to south winds and moderate to high seas through Sunday 
night. Small craft should exercise caution to low end small craft 
advisory conditions will be common through this period. The approach 
of a cold front Sunday night through Monday night will weaken the 
gradient allowing winds to become light east with lower seas.




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