Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 261115 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
615 AM CDT Wed Apr 26 2017

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

&&

.AVIATION...Patches of MVFR ceiling have reformed along with some
areas of MVFR vsby due to haze. The lower conditions are likely to
dissipate quickly this morning as much dry air mixes to the
surface in advance and behind a low pressure trough. VFR develops
shortly after sunrise and persist well into the evening. MVFR cigs
may redevelop after midnight but probabilities are low. South
winds gradually diminish this morning with winds veering
southwest to northwest late morning and this afternoon. Gusts 20
to 25 knots are possible. A weak cold front moves south of the Rio
Grande River this evening and overnight with winds turning
northeast at light to moderate speeds.

&&

.PREV DISCUSSION... /issued 403 AM CDT Wed Apr 26 2017/

SHORT TERM (Today through Thursday): At the surface a cold front
lies over Northwest Texas with a dry line/low pressure trough
extending south into Southwest Texas and Northeast Mexico. In the
mid/upper layers a strong trough over the southern High Plains
will allow for deep-layered west to northwest flow to overspread
South Texas today as it lifts northeast. This upper trough and the
approach of the cold front will set the stage for a classic down
slope event for all of Deep South Texas and RGV. Low clouds that
moved in shortly after sunset are already lifting northeast as
southwest flow begins to mix to the surface. We will see much
drier air mixing to the surface shortly after sunrise along with
compressional heating taking place as the down slope effect, off
the Sierra Madre, gets underway. As advertised, temperature to
soar well above normal with the century mark likely to be broken
along and east of interstate 69E. Records will be threaten
throughout the CWA with exception to Mcallen which has a daily
record of 107, but it may get close.

As a result of the extreme heat deep mixing of the atmosphere will
develop which will allow for stronger west to northwest winds across
the western half of Deep South Texas. Dew points and humidity crash
late morning and afternoon combining with the heat and wind
resulting in critical fire conditions. A Red Flag Warning will be in
effect from 11 am-4 pm today when the peak winds occur. Humidity
levels to remain very low into the evening hours maintaining an
elevated threat. Coastal counties will see RH values lower between
20-30 percent but winds are not expected to reach critical levels at
this time.

The cold front across the north is expected to move into the CWA
this evening and south of the River overnight. This will allow for
temperatures to cool off slightly 7 to 10 degrees overnight and for
Thursday while humidity levels recover slowly as winds turn
northeast to east off the Gulf.

LONG TERM (Thursday Night through Tuesday):
Zonal flow will begin the extended period as the large scale
trough digs across the US. The westerly flow aloft will help push
the dry desert air into the western counties Friday and Saturday,
with high temperatures reaching 100 degrees for areas west of US
281. Models prog the next cold front to sweep through the region
Sunday morning, with a marked cooldown expected. Most areas will
see a good 10 to 15 degrees cool-down for Sunday, but this still
leaves highs in the mid to upper 80s. North winds behind the front
will draw drier air further towards the coast, providing more fire
weather concerns. Lighter winds are forecast on Monday before the
surface ridge pushes east, opening the door for southeast winds
to return, bringing along more Gulf moisture.

MARINE:
Now through Thursday: Small craft advisory conditions remain in
effect through the mid morning hours. The pressure gradient is
expected to relax late this morning as a low pressure trough moves
into the Rio Grande Plains. Winds and seas to lower through the
day with winds veering south to southwest. A weak cold front moves
through later tonight with a brief period of stronger northeast
winds. This may prompt a short duration small craft advisory for
mainly the offshore waters. Northeast winds turn east and diminish
Thursday mid-morning and afternoon with southeast winds probably
returning by sunset.

Friday through Sunday: Marine conditions will be rough going
through the upcoming weekend. Friday and Saturday will see gusty
southerly winds due to inflow into the approaching cold front. The
stronger southerly winds will create significant wave action, with
swells increasing to 8 to 10 feet. Advisories are likely both
days for all marine zones. The front races through late Sunday
morning. There will be a small chance for a shower, but for the
most part the passage will be dry. North winds behind the front
will again reach 20 knots, while seas remain agitated around 8
feet. More advisories likely through the day Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  95  72  86  76 /   0   0   0  10
BROWNSVILLE          98  71  89  75 /   0   0   0  10
HARLINGEN           101  68  90  75 /   0   0   0  10
MCALLEN             102  68  93  74 /   0   0   0  10
RIO GRANDE CITY     103  66  96  73 /   0   0   0   0
SOUTH PADRE ISLAND   85  74  80  76 /   0   0   0  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Red Flag Warning from 11 AM this morning to 4 PM CDT this
     afternoon for TXZ248>250-252-253.

GM...Small Craft Advisory for winds until 10 AM CDT this morning for
     GMZ130-132-135.

     Small Craft Advisory until 10 AM CDT this morning for GMZ150-155-
     170-175.

&&

$$

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

59...short term/aviation
64...long term
65...psu graphics


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