Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 061045
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
445 AM CST Wed Dec 6 2017

.SHORT TERM (Today through Thursday): A cold front has completed its
transition through the inland portion of the BRO CWFA and through
most of the adjacent coastal waters, and light precipitation is
developing in the wake of the front. Although the precipitation will
be scattered in coverage today and early tonight, it will become
more widespread and numerous later tonight through Thursday as a 500
mb trough transitions from the Desert Southwest to the far western
portion of the Lone Star State. With overcast skies accompanying the
scattered to numerous precipitation and generally northerly winds
prevailing in the wake of the cold front, well below normal
temperatures are likely, with not much of a temperature range from
overnight lows to daytime highs.

.LONG TERM (Thursday Night through Tuesday): 500mb heights will
rapidly fall as the main mid-level trough axis moves
southeastward through Central Texas Thursday night. At the
surface, another shot of strong NNW flow will come as a 1035mb
high builds southward into West Texas. Already cool temperatures
will fall quickly into the mid and upper 30s for most inland areas
Friday morning with wind chill values dropping into the 20s.
Considering we approached record high temperatures in the upper
80s earlier this week, this will likely be a bit of a shock to
those not acclimated.

Confidence is high on precipitation chances early Friday as
moisture profiles are near 100% saturation from the surface
through the mid-levels with several weak shortwaves moving through
the main trough. Therefore, PoPs were increased as MOS guidance
remains very high through Friday morning. The main challenge to
the forecast continues to be the potential for a rare mixture of
frozen precipitation. Several model soundings consistently show a
well-saturated profile up to the -10C to -15C layer with freezing
levels dropping to near 2000ft from the mid Valley through the NW
ranchlands. The NAM remains the coldest with a mixture possible
as far east as Cameron/Willacy counties and the GFS is the
warmest, which also dries us out the quickest. Have kept a
rain/snow mix in the forecast for northern Zapata, Jim Hogg and
Brooks counties, but confidence is still low. Regardless, ground
temperatures will likely be too warm for any accumulations
despite possible wet bulbing into the low to mid 30s. Friday
afternoon the trough axis will finally dry us all out with some
clearing behind it. Unfortunately strong northwest flow and CAA
will keep temperatures in the 50s all day. Clear skies will allow
for another cold morning Saturday with lows in the mid to upper
30s.

This weekend another surface high will move southward into North
Texas, continuing to bring northerly flow and below-normal
temperatures across Deep South Texas. High pressure will finally
move into the northern Gulf and return the flow back to the south
with rebounding into the mid 70s. Towards the end of the long
term period another deep trough over the eastern U.S. may bring
our next cold front Tuesday into Wednesday.

&&

.MARINE (Now through Thursday): Buoy 42019 reported north-northeast
winds around 21 knots gusting to around 25 knots with seas slightly
under 7 feet with a period of 7 seconds at 02 CST/08 UTC. Adverse
winds and seas are occurring along the Lower Texas Coast and Small
Craft Advisories remain in effect. The Gale Watch has been delayed
until midnight tonight, and extended into the mid-morning hours of
Friday, as forecast models indicate gale force gusts are most likely
during this period. The Gale Watch has also been posted for this
same time period for the Laguna Madre. There is a high probability
that the Gale Watch will be upgraded to a Gale Warning sometime
today.

Thursday night through Monday: A 1035mb surface high will move
into West Texas, bringing another shot of strong north winds
through Friday morning. A Gale Watch continues with the
possibility of frequent gusts exceeding 34 knots. In addition to
strong winds, rain chances remain very high through Friday
afternoon. Conditions will improve Saturday as dry air returns and
high pressure builds overhead. The pressure gradient will also
relax on Saturday with diminishing winds and seas subsiding to 2
to 4 feet by Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  52  51  53  40 /  50  70  70  80
BROWNSVILLE          53  49  51  40 /  50  70  70  80
HARLINGEN            52  47  49  39 /  50  70  70  80
MCALLEN              51  45  47  39 /  50  70  70  80
RIO GRANDE CITY      51  45  47  35 /  50  70  70  80
SOUTH PADRE ISLAND   53  53  57  47 /  50  70  70  80

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Gale Watch from late tonight through Friday morning for GMZ130-
     132-135-150-155-170-175.

     Small Craft Advisory for winds until midnight CST tonight for
     GMZ130-132-135.

     Small Craft Advisory until midnight CST tonight for GMZ150-155-
     170-175.

&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

Short Term...66
Long Term...65



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