Area Forecast Discussion
Issued by NWS Brownsville, TX

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

454
FXUS64 KBRO 240546 AAC
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1245 AM CDT Fri Mar 24 2017

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

&&

.AVIATION...Multi-level cloud decks prevail across Deep South
Texas with some MVFR ceilings along and east of the I-69C
corridor early this morning. Brief MVFR ceilings will be possible
at HRL and MFE through around 08z. Moderate and gusty southeast
winds expected to continue overnight as the low level 850mb jet
strengthens to near 45 knots. Surface winds will increase later
this morning as the pressure gradient tightens as a strong storm
system moves across the Southern Plains. Winds should lessen some
as a weak front moves into the area later this afternoon.

&&

.PREV DISCUSSION... /issued 1011 PM CDT Thu Mar 23 2017/

DISCUSSION...Winds have weakened across portions of the Upper RGV
and Western Ranchlands this evening as the atmosphere has
decoupled. However, winds in the Lower Valley and near the coast
still remain somewhat elevated and likely will through the
overnight hours with a strong 850mb jet expected to develop.
Have made a few changes to the forecast to account for current
trends, with the overall forecast staying on track.

PREV DISCUSSION... /issued 715 PM CDT Thu Mar 23 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Strong and gusty SE winds will continue across the
the RGV this evening before winds decouple and lessen later
tonight. Even so, the low level 850mb jet will strengthen
overnight to near 45kts and do think that winds will occasionally
gust at the surface. However, LLWS may need to be add to the next
forecast should the surface remain more stable. Winds will
increase again Friday as strong storms system moves across the
Southern Plains with some moisture and cloud cover increasing
ahead of a pre-frontal trough that will move into the Western
Ranchlands. Winds should lessen some as it moves through late in
the period.

PREV DISCUSSION... /issued 242 PM CDT Thu Mar 23 2017/

SHORT TERM (Now through Friday night): Greater amplified
midlevel pattern continues, but remains progressive with waves and
ridges quickly sweeping through. Strong H5 ridge currently
overhead will get pushed eastward during the next 24 hours by the
deepening trough moving into the Four Corners region. Models in
agreement on the trough moving into Oklahoma on Friday, pushing a
weak cold front into South Texas. Some models continue to show a
small chance for a few showers across the northern Ranchlands, but
the main dynamics will be too far to the north, and other models
indicate that a significant area of dry air will move in aloft
early Friday, which would further strengthen the cap. Prefrontal
trough will also push across most of the region during the
afternoon, which is also a capping feature for the western
counties. Did some adjustments to the non-zero PoPs, mainly for
Brooks and Kenedy Counties, but most of the region will avoid
rainfall yet again. Breezy conditions will develop again Friday
morning due to interaction of the front/trough and high pressure
across the Gulf, but most areas will see decreasing winds later in
the day as the sfc trough moves eastward.

LONG TERM (Saturday through Thursday): A stacked low over
southern Missouri Saturday morning will lift northeast while a mid
level ridge axis moves over Texas. The next short wave trough
will follow on Sunday; upstream pressure falls will be enough to
support locally stronger winds, but there won`t be enough ooomph
to push a front past the dry line in West Central Texas. Mid level
ridging will take hold again on Monday in the up until now
rapidly evolving mid level pattern across the southern United
States. A more interesting and deeper trough will dive down the
West Coast Monday into Tuesday, bottoming as a low out over
southern California and southern Arizona Tuesday and Wednesday.
This will bring spokes of energy and upper Pacific moisture over
the Sierra Madres of Mexico and mainly into West Texas on
Wednesday. The low will eject east Wednesday night over West and
North Texas, with dry air drafting behind a front edging toward
the CWA on Thursday. Temperatures will warm Wednesday and Thursday
as 850 mb winds strengthen and veer more to south. The front will
push through on Thursday, but despite carrying limited rain
chances in the forecast, not giving it a whole lot of credence.
Relative humidity values will plummet Thursday with the arrival of
the drier air, resulting in a dry heat Thursday and Friday. To
sum up: warm, breezy and dry for much of the long term.

MARINE:
Now through Friday night: Small Craft Advisory remains in effect
for the Laguna Madre through sunset, as low level jet mixes to the
surface. Things switch overnight, as the coastal winds decrease
to around 15 knots, but winds across the open Gulf waters jump to
20 to 25 knots. The increase in winds will allow seas to increase
to 6 to 8 feet offshore tonight and continue through tomorrow. A
separate advisory will be hoisted with the next update for the
Gulf waters, starting at 7pm and running through 8am Friday
morning. Winds across the marine zones tomorrow will initially be
breezy, but a surface trough just inland will weaken the gradient
across the northwest Gulf. Weaker gradient continues Friday night,
with winds dropping to around 10 knots.

Saturday through Tuesday: Elevated seas will carry over from
Friday night into Saturday, but will settle down slightly during
the day in response to a flat pressure gradient. However, pressure
will decrease over the plains again Saturday, resulting in
stronger southeast winds late Saturday into Sunday and Sunday
night. Seas will build by Sunday under fresh southeast winds.
Conditions will improve Monday night as winds decrease. Small
craft exercise caution to low end small craft advisory conditions
will be the norm during most of this time.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds until 2 AM CDT early this morning
     for GMZ130-132-135.

     Small Craft Advisory until 8 AM CDT this morning for GMZ150-155-
     170-175.

&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

63



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.