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Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 200431 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1131 PM CDT Tue Mar 19 2019

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

.AVIATION...VFR to MVFR conditions are prevailing at the
aerodromes right now, with light rain and drizzle wafting
overhead. Model guidance suggests that the light precipitation
will end around mid-afternoon Wednesday with dry conditions 
anticipated for Wednesday night. 
&&

.PREV DISCUSSION... /issued 629 PM CDT Tue Mar 19 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Overrunning has begun to build across south Texas,
with easterly winds through about 4000, switching to westerly by
6000, per latest balloon sounding from the top of the hour. Vis 
has dropped at KBRO, and will fluctuate through the rest of the 
evening. KHRL and KMFE should also see the effects for the --RA/DZ
through the night as well, with light east to northeast winds. 
Rain chances still expected into the day tomorrow, but strength 
and timing still slightly in doubt.

PREV DISCUSSION... /issued 255 PM CDT Tue Mar 19 2019/ 

SHORT TERM (Tonight through Wednesday Night): The surface troffing 
that has generated the last several days of rainfall for the RGV is 
expected to move steadily westward tonight and should also weaken 
some as a sharp 500 mb trough axis digs across the south central 
Plains states tonight and tomorrow. This should give the region one 
more round of pcpn before drier conditions move into the region 
Wed Night. Drier and more stable air will move into the region 
late Wed as an area of 500 mb ridging builds over the RGV area. 
All of the short range model guidance indicate pretty elevated 
pops throughout tonight and early Wed with some lingering slgt 
chcs pops working into the region tomorrow night. 

The persistent cld cover in combination with a fairly cool E-NE low 
level flow pattern will hold down the temps throughout tomorrow 
night. The latest temp guidance from the NAM/GFS and ECMWF are in 
pretty good agreement and tend to hold the overall temps below climo 
through Wed Night. This looks reasonable and will stick close to a 
model blend for highs and lows. 

LONG TERM (Thursday through Tuesday): A weak upper level
shortwave ridge will allow for a very modest low level high to
form around the TX coastal bend area to start the long term period.
Surface winds will remain onshore for much of the area. Globals 
are still pinging some QPF, especially where orographic lift is 
maximized across northern Mexico and upper valley. Much of the 
region actually looks relatively dry from Thursday into much of 
Friday.

The rain chances look to increase later this weekend as an upper
level trough/surface front move into the Texas. GFS is far wetter
at the moment than ECM. Went a bit drier for now given the
uncertainty, but kept the mention of thunder as instability
increases ahead of the front. Speaking of the front, the upper
level wave misses much of Deep South Texas allowing the front to
stall north of our area at least until a stronger wave (Pacific
and Canadian impulses phase across the northern plains) digs 
southward across the eastern 2/3rds of the US. The end of the 
cycle looks to finally change the pattern just a bit with strong 
northwesterly (dry) flow aloft by the end of this forecast cycle.

Temperatures look to gradually increase through the end of this
week and into this weekend. Much of the area will end up closer 
to 80 degrees by the start of next workweek, however, as the 
aforementioned cold front moves into the region, expect 
temperatures to drop once again behind this front. 

MARINE (Tonight through Wednesday Night): Buoy020 still shows 
pretty elevated Gulf swells ongoing this afternoon. This should 
persist on through the evening and overnight hours before the PGF 
relaxes enough to allow the seas to finally drop below SCA levels 
offshore tomorrow. So will maintain the SCA for the Gulf waters as 
is with calmer conditions returning on Wed.  

(Thursday through Tuesday): Marine conditions will gradually be
improving as the long term marine period begins. The fetch across
the Gulf of Mexico will finally begin to break allowing for 
swells to decrease. Weak high pressure across the TX coastal bend 
will allow surface pressure gradient to weaken a bit. This should 
keep winds down across the marine zones through Friday. Light to 
moderate southeast flow will set up again by early this weekend. 
With sea surface temperatures still in the lower 60s, expect sea 
fog to make a comeback through this weekend and early next week. 
Atmospheric instability will gradually increases as low levels 
moisten out ahead of a cold frontal boundary next week. This may 
be enough for a few claps of thunder before rain chances decrease 
later on in the period. Our next cold frontal boundary looks to 
slide through the region by Tuesday next week. 
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 7 AM CDT Wednesday for TXZ256-257-
     351.

GM...Small Craft Advisory for hazardous seas until 7 AM CDT Wednesday 
     for GMZ150-155-170-175.
&&

$$

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