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Displaying AFOS PIL: AFDBRO Received: 2019-01-12 23:30 UTC

FXUS64 KBRO 122330 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
530 PM CST Sat Jan 12 2019

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


.AVIATION...Mostly clear skies and light to moderate northeast
winds prevail across deep south Texas early this evening. Some
passing low cloud decks should support brief IFR ceilings at BRO
through 01Z. Otherwise, VFR conditions are expected for the next
24 hours with high pressure in control. There is a very subtle 
hint at fog overnight, however due to low confidence, will not 
mention at this time. 


.PREV DISCUSSION... /issued 318 PM CST Sat Jan 12 2019/ 

SHORT TERM (Tonight through Sunday Night): After a foggy start to 
much of the region this morning, today ended up being a very 
tranquil and warm day across the region. The air is noticeably drier 
now post frontal, however, temperatures have not yet cooled (spoiler 
alert...they will later this evening). High pressure will build 
southward into the region later tonight and especially during the 
day Sunday. Stat guidance and SREF values are pinging some slight 
fog signal tonight across the middle and lower RGV. Not sold in on 
this signal as of yet as winds are expected to remain somewhat 
elevated, which should keep us just mixed enough to keep fog from 
developing. That said, the slight signal is there and protected/fog 
favored areas of Hidalgo and Cameron Counties (e.g. HWY 511 between 
Olmito and Port of Brownsville) may see some patchy fog.

High pressure continues to build into the region for Sunday.
Temperatures look cooler with ample sunshine early, however, 
increasing clouds can be expected gradually over time. A strong PAC 
upper level trough will be pushing into California by the end of the 
period. From a synoptic perspective, this will favor coastal 
troughing and indeed by the end of the cycle, guidance already 
appears to be catching this feature. Kept the short term dry, but 
isentropic lift from the coastal trough will help end the period on 
the gloomy side.

LONG TERM (Monday through Saturday): Surface ridging will prevail
over the RGV area on Mon as relatively dry and cool high pressure
spreads over the region in the wake of the fropa today. Some weak
surface troffing near the coastline will maintain a slgt chc of
some showers mainly across the eastern portions of the area. A
fast moving 500 mb short wave ejecting around the south side of
the large closed low centered near the West Coast will move over
the RGV late Tues/early Wed. This fast moving short wave will help
enhance the coastal surface troffing which will in turn help
enhance the UVV and the associated pops. This short wave is
expected move out into the Gulf of Mex by Wed Night. This will dry
out the higher RH values over the region which will in turn taper
off the pcpn chcs late Wed into early Thurs. 500 mb ridging will
briefly rebuild over the TX coastline late Wed. But another
stronger 500 mb short wave will kick out from the West Coast close
low and will move into the TX/OK Panhandle region by Thurs. This
will increase the low level WAA from the S-SE pushing the temps
back up to above January climo from Thurs through Fri. Yet 
another 500 mb trough/closed low will then dig into the South 
Central Plains States on Sat. The approach and passage of this
500 mb feature will usher a pretty strong but relatively dry cold
front through the RGV on Sat resulting in much stronger northerly
low level flow late Sat and Sat Night. 

The latest GFS and ECMWF runs are in somewhat better agreement 
today mainly concerning pops. Both models appear to be coming into
better agreement for the best pops for the RGV to be concentrated
on Tues into early Wed. The model temps are also in a little bit
better agreement today versus yesterday, but some differences
persist. Will lean towards a model blend of temps for the cooler
period on Mon and Tues. Will then go closer to the slightly warmer
ECMWF temps from Wed through Sat as believe that the GFS is
underestimating the degree of WAA expected to impact the area. 

Overall confidence is above average today due to the better
agreement indicated by the longer range model runs. 

MARINE (Tonight through Sunday Night): Marine conditions will be 
declining overnight tonight as high pressure builds southward across 
the central Plains. Pressure gradient between this high and a 
deepening low pressure across the southeast U.S. will lead to 
moderate to strong northeasterly flow across the Gulf waters.
Winds of around 20kts will be possible overnight, however, it looks 
like the SCA conditions will mainly occur between 03z and 15z. 
Because of a rather short duration and borderline winds, don't 
currently expect seas to get far above SCA thresholds at the moment. 
Gradual improvement will occur through the remainder of the short 
term, however, cautionary wording will likely continue as at the 
very least moderate northeasterly flow will persist. 

Monday through Thursday Night: The expected surface coastal
troffing along the lower TX coastline early next week will likely
maintain light to moderate NE-NE surface flow from Mon through
Wed. The surface flow will then shift around from the S-Se on
Thurs and Fri as the surface low pressure system develops across 
the southern Plains States. Low to moderate seas will prevail 
throughout most of next week. However, SCA conditions appear to be
more likely starting Sat as the next major cold front pushes 
through the region allowing stronger northerly surface flow to 
produce pretty hazardous Bay and Gulf conditions next weekend. 


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



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