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Area Forecast Discussion (AFD)

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

                            
974 
FXUS64 KBRO 220005 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
605 PM CST Sun Jan 21 2018

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

.AVIATION...Satellite images and surface observations indicate mid
to high level clouds across the northern and western portions of
the CWA early this evening. Expect MVFR to IFR conditions to
develop across the Rio Grande valley tonight as low level 
moisture increases along and ahead of a cold front morning into
the northwest portions of the CWA late tonight into early Mon
morning. IFR to LIFR ceilings/visibilities will develop early Mon
morning with low clouds and fog before the front moves through the
area Mon morning. Expect ceilings and visibilities to improve in 
the wake of the cold front from west to east Mon morning as a
result. 
&&

.PREV DISCUSSION... /issued 233 PM CST Sun Jan 21 2018/ 
SHORT TERM (Tonight through Monday Night): A weak cold front 
across west Texas this afternoon will progress into and through 
deep south Texas and the RGV tonight. The main impact will be fog 
and low clouds, which will develop for most areas with a lull in 
winds just ahead of the front. The upper valley, including the 
ranchlands and brush country, will be most affected just after 
midnight, while the lower valley will be most affected just before
dawn. The lower valley will likely see locally dense fog from 
around 3 am to 6 am. By dawn however, the front will move through,
possibly with a few sprinkles, with winds becoming moderate from 
the north, and with a drier air mass. Skies will clear out by 
Monday afternoon as high pressure spreads over the area, with high
temps for Monday in the lower 70s, and with overnight low 
temperatures decreasing into the 40s and lower 50s.

LONG TERM (Tuesday through Sunday): Continuing on Tuesday, the
upper level flow will remain from the southeast, bringing minor
shortwaves through the region through the remainder of the week.
Models are hinting that the core of the surface high will remain
to the north, allowing weak coastal troughing to develop starting
Tuesday, and continuing through Thursday. This, combined with
current timing on midlevel impulses, brings a small chance for
rainfall Tuesday night, and again Thursday. Friday the trough
weakens as the next front develops across the Texas Panhandle,
which is currently expected sometime during the day Saturday. 

MARINE:
Now through Monday night: Laguna vicinity obs appear to be close
to 20 knots with higher gusts, with a small craft advisory posted
until 6 PM. Available Gulf buoy data suggests that southeast to
south winds are still just below criteria, with a SCEC in effect
offshore. Winds will decrease tonight as a cold front approaches
the area. Fresh north winds behind the front on Monday will result
in SCEC conditions overall with possible low end small craft
advisory conditions for the Gulf beyond 20 nm. Winds will decrease
Monday night, but swells near seven feet offshore may take a bit
longer to abate.

Tuesday through Thursday: Marine flow remains from the northeast
Tuesday and Wednesday as a weak coastal trough develops further
offshore. This will keep wave heights agitated at 4 to 6 feet. The
coastal trough weakens starting Thursday, with winds shifting more
easterly, but remaining in the 10 to 15 knot range. This keeps
swells around 5 feet through Thursday night.

FIRE WEATHER...Dew points and relative humidity values will crash 
Monday behind a cold front. RH values will drop into the teens for 
most areas by afternoon. Winds at 20 feet will be right around 15 
mph through about noon, and with fuels being cured there could be a 
period of enhanced to critical fire weather parameters and enhanced 
wildfire growth and spread.
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds until 6 PM CST this evening for 
     GMZ130-132-135.
&&

$$

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