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Area Forecast Discussion (AFD)

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

FXUS64 KBRO 151140 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
640 AM CDT Wed Aug 15 2018

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


.AVIATION...The latest IR satl imagery from the RGV indicates a
few patches of lower level cld cover around the RGV area. This
may result in some brief reductions of the ceilings down to MVFR 
levels at the MFE and HRL airports. For now will not include a
mention of this in the current TAF wording. The daytime heating 
expected later today will mix out the lower levels of the atms to 
maintain VFR conditons for the bulk of the upcoming TAF period. 


.PREV DISCUSSION... /issued 404 AM CDT Wed Aug 15 2018/ 

SHORT TERM (Now through Thursday): The 500 mb ridging will be 
strengthening over TX throughout the short range period as the 
closed low over the Mid Miss River Valley continues lifting out to 
the NE. The strengthening ridge axis will increase the overall 
stability over the RGV while steadily decreasing the overall atms 
moisture levels in place over the region. Enough moisture may reside 
near the coastline and out over the lower TX Gulf waters to maintain 
the potential for some isold marine conv throughout Wed Night and 
will handle these with some 10-20% pops with near zero pops inland. 
Daytime heating may fire off a shower or two mainly during the 
afternoon and early evening hours, but will not include any 
significant pops at this time due to the increasing influence of the 
ridge axis.  

Expect temps for the RGV to remain near persistence for Wed and 
Thurs as the ridging gradually builds. Will go closer to the ECMWF 
temp guidance through Thurs as this guidance appears to be the 
warmest of the three short term model temps. 

LONG TERM (Thursday Night through Tuesday): Hot and generally 
rain free conditions will continue through the period with high 
pressure aloft and at the surface. An inverted mid level trough 
approaching Mexico may support isolated seabreeze activity Friday 
through Sunday. Rain chances will remain low through the rest of 
the period but can't rule isolated sea breeze convection by
midweek as slightly deeper moisture arrives. Temperatures are 
expected to remain above normal through the period. High 
temperatures each day will generally range from the low to mid 90s
in the lower Valley to the upper 90s to the triple digits in the 
mid to upper Valley with overnight lows in the 70s to around 80 
degrees. Heat index values will generally range between 105-109 
degrees each afternoon across much of the deep south Texas. 

MARINE (Now through Thursday): Broad surface ridging will remain in 
place over the western Atlantic and all of the Gulf of Mex through 
Thurs. This surface ridge will maintain a strong enough PGF over the 
Laguna Madre in order to push the surface winds up close to SCEC 
crit for this afternoon and Thurs afternoon.  

Thursday night through Sunday Night: Surface high pressure across
the Gulf and lower pressure upstream will support light to 
moderate winds and moderate seas through period. The gradient will
gradually increase late in the weekend with small craft exercise 
caution conditions developing for portions or all of the adjacent 
Gulf of Mexico waters by Sunday.




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Short Term/Aviation...60
Long Term...63
Graphicast/Upper Air...62