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Area Forecast Discussion (AFD)

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

FXUS64 KBRO 210014 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
614 PM CST Sun Jan 20 2019

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


.AVIATION...A very dry airmass over the RGV area will maintain VFR
conditions across the region over the next 24 hours. The dry 
surface ridge will shift steadily eastwards tonight into Monday. 
This will allow the surface winds to shift around and increase 
from the S-SE after sunrise tomorrow. 


.PREV DISCUSSION... /issued 251 PM CST Sun Jan 20 2019/ 

SHORT TERM (Tonight through Monday Night): 500mb ridge across 
northeast Mexico and the south-central United States tonight will 
continue to provide subsidence across the CWA tonight into Monday 
before the upper level ridge flattens and shifts eastward Monday. At 
the surface...high press across the Texas coast tonight will shift 
eastward as low pressure develops on the lee side of the Rockies. 
This will allow the pressure gradient to increase across the lower 
Texas coast Monday into Mon night. Breezy conditions will develop 
across the Rio Grande valley and northern ranchlands Mon afternoon 
and continue into Mon night. Clear skies and light winds tonight 
will allow temperatures to fall into the 40s by early Mon morning 
with radiational cooling. Temps will warm into the 70s Monday as 
warm air advection returns and the lack of cloud cover enhances 
diurnal heating. Lows will be considerably warmer Mon night with the 
stronger southeast flow across the area.

LONG TERM (Tuesday through Sunday): Warm and windy conditions are 
expected on Tuesday as the pressure strengthens and southerly flow 
continues. Temperatures will remain well above normal on Tuesday 
with as highs should reach the upper 70s to around 80. Model 
guidance continues to indicate a small opportunity of a wind 
advisory on Tuesday. Rain chances are expected to increase Tuesday 
night into Wednesday morning as a cold front moves into deep south 
Texas. The best chance of showers will mainly be along the front 
with some enhancement near the coast. Low temperatures Tuesday night 
should range from the upper 40s across the Ranchlands to the mid 50s 
along the beaches. High temperatures Wednesday will struggle to 
reach 60 degrees due to strong CAA and cloudy skies. Rain chances 
end from west to east as the 500 mb short wave passes overhead with 
dry air filters into the region. 

Low temperatures Wednesday night are expected to fall into upper 30s 
to the lower 40s under mostly clear skies. Wind chill values may 
drop into the upper 30s to around 40 degrees with modest light north 
winds. Surface high pressure spreads across the region on Thursday 
as temperatures slowly recover. High temperatures Thursday and 
Friday will be generally in the 60s. Low temperatures Thursday night 
should be in the 40s with mostly clear skies. Weak reinforcing 
surface high pressure will arrive Friday night into Saturday 
morning allowing mild temperatures to persist. 

MARINE (Tonight through Monday night): Seas were near 6 feet with 
north to northeast winds near 12 knots at buoy020 early this 
afternoon. Light east to southeast winds will prevail across the 
coastal waters tonight as surface high pressure across the lower 
Texas coast moves eastward. Winds will increase from the southeast 
Monday as the pressure gradient increases across the western Gulf of 
Mexico with low pressure developing on the lee side of the Rockies. 
Moderate southeast winds Monday will increase Monday night and small 
craft advisories will likely be needed for the coastal waters Mon 
night as a result as the pressure gradient continues to tighten 
across the lower Texas coast.

Tuesday through Friday night...Strong south winds will continue 
on Tuesday as the pressure gradient continues to interact with 
higher pressure across the Gulf. A Small Craft Advisory will 
likely remain place on Tuesday. A cold front is expected to arrive
Tuesday night into early Wednesday morning allowing winds to 
briefly diminish Tuesday night. Strong winds will develop in the 
wake of the front on Wednesday, with possible gale force gusts on 
the Gulf. Marine conditions will gradually improve Wednesday night
as high pressure spreads across the northwest Gulf. 

FIRE WEATHER...20 foot winds will increase from the southeast 
around 15 knots Monday afternoon as temperatures in the 70s and 
dewpoints in the 50s provide relative humidity values between 40 and 
50 percent across most of the CWA. These conditions will be below 
Red Flag Warning conditions so no fire weather watch is needed but a 
fire danger statement will likely be needed for portions of deep 
south Texas tomorrow especially if winds are higher/relative 
humidity values are lower than currently forecast.

Models continue to suggest the combination of dry air, low 
relative humidity values and cured fuels will be in place on 
Wednesday afternoon behind the front. There is an elevated threat 
of erratic fire behavior and rapid spread potential on Wednesday. 




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Short Term/Aviation...60
Long Term...64
Graphicast/Upper Air...67