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Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 161530 AAB
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
930 AM CST Sat Feb 16 2019

.DISCUSSION...Surface observations show dense fog persisting
across portions of the ranchlands and out west, so have extended
the Dense Fog Advisory for Zapata and Jim Jogg an hour until 10 AM
CST. Some thinning in the cloud cover is evident on satellite
imagery, so conditions should improve fairly quickly.

Also extended the Dense Fog Advisory along the coast until noon
CST today. Local webcams show low visibilities across the Laguna
Madre and in the nearshore Gulf waters. Conditions should improve
in the next couple hours with more sufficient daytime mixing.

&&

.PREV DISCUSSION... /issued 648 AM CST Sat Feb 16 2019/ 

DISCUSSION...Have updated the forecast to include a Dense Fog
Advisory for Zapata and Jim Hogg counties as surface obs from
these two counties show that dense fog have formed up. These areas
of dense fog will persist across these two counties through 
around midmorning and should dissipate afterwards as the daytime
heating increases.

PREV DISCUSSION... /issued 603 AM CST Sat Feb 16 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...IR satl imagery shows a widespread low stratus deck in
place across most of Deep South TX and the RGV reducing conditions
down to IFR levels. These low ceilings will prevail through the
mid to late morning hours with the daytime heating and increased
low level mixing gradually improving the ceilings later today and
this afternoon. The VFR conditions expected this afternoon and
early this evening will give way to lowering ceilings and IFR
conditions once again after sunset as the moist nocturnal low 
level inversion reforms. 

PREV DISCUSSION... /issued 358 AM CST Sat Feb 16 2019/ 

SHORT TERM (Now through Sunday): A fairly zonal 500 mb pattern 
will prevail across TX today with most of the better PVA located 
well north of the region. The 00z BRO sounding shows pretty 
limited moisture levels in place over the RGV last night and early
this morning. So expect nil pops today and tonight. The 
persistent low level WAA today and tonight will maintain temps 
well above normal for mid Feb. A series of 500 mb short waves 
moving across the Rockies and the central Midwest Sat Night and 
Sun will push a cold front through the RGV on Sun. Decent CAA in 
the wake of this fropa will lower down the high temps on Sun 
closer to Feb climo. Some decent moisture levels pool over the RGV
ahead of this approaching cold front. This will produce some 
better conv chcs across the RGV on Sun.

Will lean closer to the warmer GFS/ECMWF numbers for the short term 
forecast period as believe that the NAM may be underestimating the 
expected warmup this morning.

Will include some areas of fog across the region this morning. At 
this point the fog formation has been a bit lighter versus 
yesterday. So do not anticipate a Dense Fog Advisory across the 
inland areas this morning. 

The more SE low level flow today will tend to suppress the 
potential downsloping heating effect on the daytime highs today. 
So do not expect any record highs reached or exceeded today.

LONG TERM (Sunday Night through Friday): The next Pacific NW
trough continues to drop into the Desert SW and deepen into mid 
week, with little to no movement expected over the next week.
The frontal boundary from early Sunday hangs around across the SE
US and northern Gulf of Mexico, with persistent low pressure 
along the boundary and lower Texas coast keeping the long term 
rather unsettled. Models have stayed relatively consistent on the 
pattern, yet differ on the smaller intricacies across Deep South 
Texas as each bout of low pressure spins by the coast and frontal 
boundary. Latest runs have spun up the initial coastal low on 
Monday, with rain chances holding off until Monday evening. After 
Monday night, light rain persists along the coast into early 
Thursday, with isolated pops into Friday. 

Temperatures rebound near normal on Monday, but struggle to gain
any further, with increasing clouds, moisture, and stiff NE winds.
While the models have trended warmer for Tuesday, due to a surface
low near the border potentially picking up southerly winds, have
opted to keep temperatures tampered slightly, as this feature
could vary quite a bit over the next 3 days. A return to
increasing NE winds and continued overrunning situation yields
cooler temperatures on Wednesday still, with some improvement
expected Thursday and Friday, allowing temperatures to gradually
warm. Models have begun to show the trough heading toward the
Midwest next weekend, finally clearing the pattern with an
associated cold frontal passage across Deep South Texas. 

MARINE (Now through Sunday): A general light to moderate SE 
surface wind flow will prevail across the lower Texas coastline as
surface ridging remains in place over the Gulf of Mex. The low 
level flow will then shift around from the northeast to north late
Sun which may build up the Gulf seas a bit. However, no SCA 
conditions expected through Sun. 

Sunday Night through Friday: Marine conditions may become 
hazardous early Monday as coastal low pressure begins to spin up.
SCAs likely by Monday afternoon continue into Tuesday before 
lighter winds allow conditions to improve slightly. By Wednesday, 
NE winds pick up and agitate seas once again into Thursday with 
SCA conditions possible. Winds and seas begin to improve late in 
the week prior to a cold frontal passage next weekend. 

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 10 AM CST this morning for TXZ248-249.

GM...Dense Fog Advisory until noon CST today for GMZ130-132-135-150-
     155.

&&

$$

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Update...65