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Area Forecast Discussion (AFD)

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

FXUS64 KBRO 152352 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
552 PM CST Fri Feb 15 2019

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

.AVIATION...The main concern tonight will be fog. Model guidance
suggests that fog will form at the aerodromes during the overnight
hours, but the intensity will likely be dictated by the strength
of the winds, and visibilities could easily be better or worse
than indicated in the current suite of TAFs. Full VFR is likely
tomorrow after sunrise. 

.PREV DISCUSSION... /issued 311 PM CST Fri Feb 15 2019/ 

SHORT TERM (Now through Saturday night): Overall synoptic 
pattern includes zonal flow aloft with a very dry atmosphere from 
the near- surface up to 300mb, with only enough moisture for some 
upper-level cirrus clouds this afternoon. In the low levels, winds
have picked up to 25 mph at times out of the S to SSW. This, 
combined with mostly sunny skies, has led to well-above-normal 
temperatures this afternoon across all of the CWA. A few locations
may hit 93 to 95F before peak heating ends in the next hour or 
so. Mild conditions are expected this evening with above-normal 
lows overnight. The main concern in the short term will be fog 
potential. We are already seeing some marine fog develop, as 
expected, this afternoon. And models indicate some radiational fog
will develop overnight. Patches of dense fog will be possible if 
winds can lighten just enough.

Saturday will be another warm day, but should be a couple degrees 
cooler than today. Models bring a weakening front in the northern 
areas of the CWA, with only a mild backing of winds to the east and 
possibly northeast up north. Still, the atmosphere is very warm in 
the low levels, so above-normal temperatures are anticipated, with 
highs in the upper 80s to low 90s out west. Continued to go well 
above all model guidance, which has worked out so far today. If 
light easterly flow develops along the coast, a sea breeze will be 
possible, dropping temperatures a bit more Saturday afternoon. 
Regardless, moisture will be very limited, with models showing RH 
values of 30% right off the surface and into the mid levels.

LONG TERM (Sunday through Friday): A period of unsettled weather
is anticipated for the long term as a cold front moves through on
Sunday with an upper Western U.S. trough to set up and remain 
quasi- stationary over the Desert SW until next weekend. 

Model are in overall good consistency with the west coast trough but 
differ in timing in the west to east movement of shortwaves and 
disturbances within the developing deep southwest flow. Temperatures 
begin to fall later Sunday with a more substantial drop to below 
normal highs and lows Monday-Friday and may even linger into next 
weekend with the trough axis remaining west of Texas and a coastal 
trough/low lingering over the Western Gulf keeping our region in a 
generally cool north-northeast surface flow. As for precipitation 
chances probabilities trend upward post front but vary with the 
passage of the mid/upper level disturbances and proximity of the 
coastal troughing or weak low pressure area(s) that may form along 
the coastal trough/old frontal boundary.  

As for guidance pops and temperatures MEX/EC are in pretty good 
agreement with both models pointing towards Wednesday and Thursday 
as the coolest and wettest days of the week. Expect the forecast to 
be advised day to day with lower confidence in timing of the 
disturbances within the SW flow. 

MARINE:(Now through Saturday night): The main concern with the 
coastal waters will be fog potential. We are already seeing marine 
fog develop along the nearshore Gulf waters, and is verified on 
visible satellite and local webcams. Have issued a Marine Statement 
for low visibilities, but conditions will need to be monitored for a 
possible advisory if fog expands or thickens this evening and 
overnight. Otherwise, moderate southerly winds will keep seas at 3 
to 5 feet offshore and around 2 to 4 nearshore ahead of a weak front.

Sunday through Thursday: Moderate cold front moves through the 
coastal waters Sunday afternoon and pulls up stationary near the 
Lower Texas coast Monday and lingers nearby through much of the 
week. A moderate to occasional strong north to northeast flow 
provides unsettled marine conditions much of the period. The days 
with the most unsettled conditions, which might warrant small craft 
advisories, look like Sunday night and Monday then again Wednesday 
into Thursday.  



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