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Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 161652 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1152 AM CDT Tue Apr 16 2019

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

&&

.AVIATION...The morning sounding at BRO showed a significant cap 
from 900 to 800 mb, and a moderate low level jet in that layer. 
Low clouds have been in and out, with enough mixing and drier air 
to prevent complete overcast while allowing some peeks at the sun.
Still seeing MVFR ceilings at times. A tighter surface pressure 
gradient is supporting breezy to wind and gusty conditions, with 
southeast winds of 25G35 mph typical. The stronger southeast winds
will continue through the afternoon, and will only drop back to 
moderate tonight. Low level moisture is forecast to increase this 
evening and overnight, with low level clouds thickening in the 
process, with model guidance suggesting MVFR conditions setting up
around sunset and going through the night and into Wednesday 
morning. An isolated sprinkle will even be possible near the coast
overnight. Forecast soundings show a strong cap remaining in 
place through tonight and Wednesday, so MVFR ceilings developing 
as low level moisture increases seems reasonable. Breezy southeast
winds will develop again on Wednesday, though they will be a 
skosh less than today.

&&

.PREV DISCUSSION... /issued 559 AM CDT Tue Apr 16 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Brief morning low clouds are drifting through the
region this morning, but are only briefly thickening to BKN. Have
reduced TAF to tempo group for early morning, with SCT the
remainder before noon. Windy conditions still expected, with
sustained winds of 25kts at KBRO and KHRL, with frequent gusts
around 35. Breezes only reduce to 15 to 20 knots after sunset and
continue through the night tonight.

PREV DISCUSSION... /issued 358 AM CDT Tue Apr 16 2019/ 

SHORT TERM (Now through Wednesday): The region will be well- 
placed between strong surface high pressure to the east and 
developing low pressure in SE Colorado today. This will tighten 
the gradient, allowing southeast winds to ramp up quickly this 
morning. Winds will reach near 25 knots along the coast and around
20 knots further inland. Warm temperatures will also continue 
today, with highs rising into the upper 80s and lower 90s. 
Tonight, the leading edge of the next H5 trough moves into Texas, 
bringing some midlevel lift to the region. While capping will 
still be somewhat persistent, the lift aloft may be enough to 
spark a few streamer showers right along the coast after midnight 
tonight, and continuing through the noon hour. About that time, 
some wraparound dry air reenters the region, restrengthening the 
capping inversion. This will decrease rain chances and will likely
push temperatures well into the 90s areawide.

LONG TERM (Wednesday Night through Monday)...Main weather impacts
for deep south Texas will be Wednesday night into early Thursday 
morning as the 500mb low/trough across northwest Texas/northern
Mexico Wednesday provides showers and thunderstorms...some strong
to severe...across northeast Texas extending southwest towards
southwest Texas. There still exists the potential of a linear
convective system (squall line) developing across the Rio Grande 
plains Wed night and possibly moving across the northern
ranchlands as a Pacific cold front moves into southwest Texas.
The primary severe weather threat with the squall line would be 
damaging wind gusts. Not sure how strong the cap will be across
the northern ranchlands Wed night but it will likely erode as the
convective line moves across the Rio Grande plains. Farther 
south...the cap will likely be strong enough to prevent showers 
and thunderstorms from developing across the Rio Grande valley 
until the front moves into the RGV Thurs morning. Will continue to
mention a slight chance to chance of showers and thunderstorms Wed
night into Thurs morning. Will also mention gusty winds with
thunderstorms across the northern ranchlands Wed night. 

Once the front moves through the CWA Thurs morning...drier air
will filter into the Rio Grande valley Thurs afternoon and
subsidence will increase across southwest Texas Thursday into
Friday as the upper level low/trough across the southern plains
moves eastward. Surface high pressure will settle across the
western Gulf of Mexico Friday and moving eastward Saturday into
Sunday allowing an onshore flow to return Saturday and increase
Sunday.  

Very warm and breezy conditions will prevail on Wednesday with
above normal temperatures. Breezy conditions will prevail in the
wake of the front Thursday with slightly cooler temperatures but
still above normal. Cooler air will filter into the area Thurs
night into Friday with more seasonable temperatures Friday. Breezy
and warm conditions will prevail across deep south Texas through
the Easter weekend into early next week with no chance of rain
Saturday through Monday. 

MARINE (Now through Wednesday): Strong southeast flow continues 
today, due to tighter gradient between high pressure to the east and 
low pressure building over southeast Colorado. Winds will reach 20 
knots soon and will continue through the remainder of the day. Small 
Craft Advisories are in effect for the open Gulf waters already, and 
will start for the Laguna Madre at 10am. Expect breezy conditions to 
continue through the remainder of the day, and will likely continue 
through the night into Wednesday morning.

Wednesday night through Saturday...Moderate to strong south to
southeast winds will prevail across the coastal waters Wed night
before a Pacific cold front moves offshore the lower Texas coast
Thurs afternoon. Winds will shift to the northwest in the wake of
the front and increase from the north Thurs night. Small craft
advisories will likely be needed for the bay waters Wed night and
Thurs night and for the offshore waters Wed night through Fri 
morning. Winds and seas will diminish across the western Gulf of
Mexico Friday as surface high pressure settles across the area.
Light north winds Friday will veer to the south Fri night and
increase Saturday as the pressure gradient increases across the
lower Texas coast with low pressure developing across eastern
Colorado and surface high pressure across the western Gulf.

FIRE WEATHER...Relative humidity values are expected to fall
below 25 percent west of Interstate 69E Thursday afternoon as
drier air filters into the Rio Grande valley in the wake of the
Pacific cold front moving through the area Thursday morning. In
addition...winds are expected to increase from the northwest in
the wake of the front with 20 foot winds of 15 to 25 mph
developing across the CWA especially across the western portions
of deep south Texas. This will provide elevated to critical fire
weather conditions across portions of Zapata...Jim Hogg and Starr
counties Thurs afternoon. 

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds until 6 PM CDT this evening for 
     GMZ130-132-135.

     Small Craft Advisory until 6 PM CDT this evening for GMZ150-155-
     170-175.

&&

$$

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