Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 090406 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1006 PM CST Fri Dec 8 2017

.DISCUSSION...Earlier, had made some tweaks to hourly temps,
mainly along the immediate coast. Left overnight minimum temps
largely as inherited, though. Short-term guidance has been
consistent so kept Saturday morning lows a couple degrees below
model consensus, as done on previous shift. A few sheltered
locations may touch 32 degrees late tonight for an hour or so, but
confidence lacking for meeting Freeze Warning criteria: Even where
temperatures are starting out colder in the Lower Valley,
dewpoints remain in the mid-upper 30s. Farther northwest, current
dewpoints are just above freezing and temps remain in the mid-40s
at this hour with winds expected to stay up at 5-10mph the rest of
the night. H85 temps also progged to actually rise a degree or two
overnight to boot. Wind chill values will dip below 30 across the
southern-tier counties, but winds will remain below 10mph. Relevant
text products have been updated.


.DISCUSSION...Updated for latest marine discussion below.


.MARINE...Updated winds with latest National Blend guidance but
left seas alone. Gridded forecast didn`t change much, and with
little to no data to validate current trends (save a 23Z report
from TABS-K buoy), left current headline configuration intact.


.PREV DISCUSSION... /issued 552 PM CST Fri Dec 8 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Clouds have pretty much cleared the Rio Grande Valley
airports, per latest IR satellite imagery. Skies expected to
remain clear through the TAF period with VFR prevailing. Modest
WNW winds of 5-10 knots overnight become more NW and moderate by
late morning on Saturday. With the damp ground and decent
radiational cooling conditions overnight, will have to keep an eye
on any shallow ground fog. However, confidence is low with progged
max relative humidities only reaching ~85% and winds remaining
somewhat elevated. With only NAM MOS even hinting at the mist/fog
possibility (for HRL) amongst the various will leave
out of TAF`s at this time.

PREV DISCUSSION... /issued 427 PM CST Fri Dec 8 2017/

SHORT TERM (Tonight through Saturday Night): After a taste of
winter (with some biting off a little more than they can chew in
the northern Ranchlands), wintry precip has cleared the region
this afternoon. Intense snowfall rates as well as much of the
heavier snowfall happening overnight helped overpower warm ground
temps leading to a 3-5 inch or so swath of snow from southern
Zapata into northern Brooks County (and beyond). Another band fell
from central Hidalgo into Willacy County, however, this band only
had 1-2" since it occurred after sunrise this morning. The
significance of knowing what locations have a snow-pack and which
locations do not will play into the overnight low temp forecast
for tonight. Decided for these areas to go ahead and undercut
guidance a bit, but still managed to keep all the CWA above
freezing due to surface winds remaining a bit elevated. Will issue
SPS for the northern tier given the close proximity to the
freezing mark overnight.

The H500 long wave will remain centered across the eastern 2/3rd of
the nation through this weekend. This will translate to continued
below average temperatures, however, with the sun coming back we
will finally break out of the 40s and back into the 60, perhaps
closer to 70 degrees by Sunday.

LONG TERM (Sunday through Friday): A pattern change next week will
be tough as a Rex Block sets up over California.  This will continue
to allow dry northwesterly flow aloft with little in the way of
rainfall, at least through midweek week.

A weak Pacific frontal boundary is forecast to slide down the
eastern side of the Rockies by Thursday. This will not have much
impact on the area, but may help drop temperatures just slightly.
There is a very slight QPF signal toward the end of the cycle,
however, kept everything slight at the moment as confidence is
fairly low, at least in the precip category.

MARINE: The PGF will be steadily weakening over the lower TX
coastline through tonight into the weekend and next week as weak
surface ridging prevails over the region. However, the elevated Gulf
swells will need some time in order to decrease somewhat. So will
replace the Gale warning offshore with a Small Craft Advisory and
will allow the Gale warning to expire across the Laguna Madre.
Much calmer Bay and Gulf conditions expected after tonight and
Saturday as the pressure gradient remains weak.


GM...Small Craft Advisory until noon CST Saturday for GMZ170-175.

     Small Craft Advisory until 3 AM CST Saturday for GMZ150-155.



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