Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 241021

Area Forecast Discussion
National Weather Service Brownsville TX
421 AM CST Sat Feb 24 2018

.SHORT TERM (Today through Sunday): Shortwave trough moving out of
the Rockies and into the Plains today/tonight with surface low
pressure deepening. Low level jet strengthening as of this writing
with 925-850 winds increasing to the 35-45kt range this
morning/early afternoon. The stronger winds to partially mix to the
surface later this morning with deeper mixing this afternoon as
lapse rates increase as surface temperatures climb well into the 80s
and lower 90s. Strongest winds are still expected over the Lower
Valley and the Coastal regions warranting a wind advisory across
Cameron and Willacy and Small Craft Advisories for the coastal

Tonight into Sunday...Broad upper trough with deep southwest flow
will be the forebears of a slow moving cold front and upper level
impulses increasing the chance for showers and thunderstorms. An
elongated impulse moving out of Mexico this evening/tonight to
initiate thunderstorms and with the strengthening upper jet
atmosphere dynamics become marginally favorable for some strong
storms with an isolated severe storm not out of the possibility.
Strong winds and some marginally severe hail along a southwest to
northeast path from the Zapata, Starr to jim Hogg/Brooks counties
look like the best locations with increasing 0-6km shear values into
the 40-55kt range and MU CAPE values 1200-2000j/kg range expected in
these areas. Northern Hidalgo can not rule out a strong storm as the
storms track eastward but believe much of the I-2 and lower portions
of the 69C/E regions may escape the strongest storms tonight. The
front enters the CWA Sunday morning and moves south at a snails pace
through the day. GFS shows a few stronger vort maxes moving across
the region during the day and with dynamics still in place for a few
clusters of thunderstorms are still possible this time favoring
counties farther to the east. Expect some pockets of heavy rain with
Pwats well above normal can not rule of some localized flooding in
poor drainage areas where showers or thunderstorms could taking on a
training affect. Temperatures to cool off towards normal behind the
front but with the slow eastward progress temperatures in the Lower
Valley to approach or exceed 80.

.LONG TERM (Sunday Night through Friday): The long term starts
with a cold frontal boundary through the region late Sunday and
early Monday. Although the front remains parallel to the upper
level southwest flow, mesoscale influences will help push the
surface front just south of the mouth of the Rio Grande by early
Monday. As the front stalls just south, expect isentropic lift to
keep clouds and showers/drizzle around the region on Monday.
Daytime high will also be cooler as CAA and cloudy conditions
keep temps down on Monday. The front decides to roar back
northward as a warm front on Tuesday allowing southerly return
flow to help push drizzle/showers/fog potential northward out of
the CWA.

Behind the warm front WAA will help boost temperatures on Tuesday
and especially on Wednesday as southwest FA may jump into the
lower 90s. Winds will also begin to pick up on Wednesday due to
1)intense surface warming allowing afternoon mixing and 2)
increase in surface pressure gradient between a departing high
east and troughing west. The front should finally push through the
region overnight (should be a mostly dry passage). High pressure
drops southward into eastern Texas by early Friday helping relieve
some of the breezy conditions. As this high pushes eastward into
the southeast, coastal troughing may form by early next weekend,
which will keep the area cloudy, cool, and damp.


.MARINE (Today through Sunday: Pressure gradient continues to
strengthen as low pressure moves out of the 4 corners region and
into the Southern/central Plains through tonight. Southerly flow
strengthens this morning with increasing winds and building seas
through the day. Small Craft Advisories are in place for later this
morning and into the early evening hours. A cold front moves into
South Texas overnight and slows down considerably moving off the
coast late Sunday into Sunday night. Winds and seas to slowly lower
as the gradient weakens with the approach of the front while showers
and thunderstorms will be on the increase.

Marine fog remains patchy at best with occasional patches of dense
fog over the near shore waters. A Dense fog advisory will remain in
effect until mid morning when the onshore flow strengthens and some
mixing of slight drier air works its way to the surface.

(Sunday Night through Friday): Moderate winds and seas expected as
we begin the long term period as coastal trough sets up just off
shore. Very little improvement expected through much of the week,
in fact conditions will slowly decline by midweek as a cold
frontal boundary moves through the region Wednesday night or early
Thursday. This will push winds/sea close to if not exceeding
Small Craft Adv thresholds. High pressure will then drop into
eastern TX which may help bring seas and winds down finally by
Friday...though the easterly fetch across the Gulf may increase
swells the end of next week.


BAYVIEW/PORT ISABEL  86  68  77  64 /  10  20  40  40
BROWNSVILLE          86  69  79  64 /  10  20  40  40
HARLINGEN            87  68  77  63 /  10  30  50  30
MCALLEN              91  67  75  62 /  10  40  50  30
RIO GRANDE CITY      91  66  73  60 /  10  60  40  20
SOUTH PADRE ISLAND   75  68  73  64 /  10  20  40  40


TX...Wind Advisory from 11 AM this morning to 5 PM CST this afternoon
     for TXZ254>257.

GM...Small Craft Advisory for winds from 10 AM this morning to 6 PM
     CST this evening for GMZ130-132-135.

     Small Craft Advisory from 10 AM this morning to 9 PM CST this
     evening for GMZ150-155-170-175.

     Dense Fog Advisory until 10 AM CST this morning for GMZ150-155.



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