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Area Forecast Discussion (AFD)

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

                            
198 
FXUS64 KBRO 200523 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1123 PM CST Mon Feb 19 2018

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

&&

.AVIATION...Brisk southerly winds will continue overnight and 
through the daytime on Tuesday. Some gusts will approach 30kts 
from time to time. The other story will be a low stratus deck 
sitting over our terminals this evening and into the Tuesday as 
well. MVFR conditions initially will decline a bit to perhaps IFR 
overnight and through the morning hours for BRO and HRL. There 
should be some slight improvement by late morning. MFE has the 
best potential for VFR Tuesday afternoon. The stratus deck 
eventually lowers back to MVFR toward the end of this cycle. 

&&

.PREV DISCUSSION... /issued 536 PM CST Mon Feb 19 2018/ 

..00z Aviation Update...

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...A fairly active TAF cycle ahead, especially tonight.
First, winds will begin to subside slightly this evening, however,
gusts of 20kts at times will still be possible as a strong
pressure gradient remains. A low stratus deck will also bring
conditions down from VFR to IFR later tonight for HRL and BRO.
Low end MVFR can be expected for MFE. Flight conditions should
slowly improve tomorrow (MVFR east and VFR for MFE). Another
breezy day is expected with southerly winds gusting up to 30kts.

PREV DISCUSSION... /issued 238 PM CST Mon Feb 19 2018/ 

LONG TERM (Wednesday through Monday): A weak cold front will push 
into the CWA on Wednesday, mainly affecting the ranchlands and brush 
country with showers and thunderstorms, though more so Wednesday 
night. Can't rule out thunder for the Lower Valley (LV), but the 
boundary will struggle to make it all the way through, and mid level 
ripples in the flow will likely not be enough to break the cap for 
deeper convection over the LV. Model guidance is also less certain 
with LV thunder so will maintain or reduce coverage slightly from 
the inherited package. Not expecting any drastic change in temps with
the front. High temps will be a few degrees lower on Thursday, but 
still above average. Return flow should redevelop on Thursday as a 
West Coast short wave trough pushes into the Southwest, supporting 
pressure falls over the southern High Plains, with rain chances 
decreasing late in the week as the remnant front retreats north.

A second, slightly deeper short wave trough will dive south out of 
the Pacific Northwest late in the week, and into the Southwest by 
Friday. This time a surface front will push through Saturday night, 
but the mid level trough will again be well to the north by then, 
unable to provide strong upper dynamics. Moderate north to northeast 
winds will develop on Sunday behind the front. All in all, did not 
make a whole lot of changes to the inherited forecast.

MARINE:
Now through Tuesday Night: Surface/Buoy obs near the lower TX
coastline in addition to a recent ASCAT satl pass over the region
around 18z indicates that the surface winds are pushing into SCA
levels for the Bay waters but are struggling to reach SCA criteria
for the offshore waters this afternoon. A strong PGF persists across
the lower TX coastline today, but the downward mixing of the LLJ has
been limited due to fairly cool surf water temps near 60. As the
marine air temp cools down somewhat later tonight this could weaken
the low level marine inversion to allow some stronger winds to mix
down to the surface. So the SCA for Winds for the Gulf waters will 
likely need to be extended through the overnight hours into Tues 
morning. The PGF will then start to weaken somewhat throughout the 
day Tues and into Tues Night which may reduce the chances for more 
SCA conditions.

Wednesday through Saturday night: Moderate southeast to south winds 
and moderate seas will prevail through the long term forecast as high
pressure to the east dominates the Gulf. A cold front will push 
close to the coast on Wednesday, but is currently forecast to pull up
short of the Gulf waters. Small craft should exercise caution 
conditions may develop from time to time.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until noon CST Tuesday for GMZ150-155-170-
     175.

&&

$$

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