Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 081230 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
630 AM CST Fri Dec 8 2017

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


.AVIATION...Widespread light to locally moderate snow showers
continue across much of the area early this morning and will
persist through mid morning. Rain is trying to changeover at BRO
and HRL but the 12Z sounding from KBRO shows a warm nose at 700mb,
which is causing a lag. Airport conditions are poor with overcast
low IFR ceilings and reduced visibilities expected to continue
through early afternoon in addition to the possibility of minor
slushy accumulations.

A mid-level trough axis will sweep through the area with dry air
and clearing skies tonight. Temperatures will drop to near
freezing in a few locations with patchy frost being possible.
Winds will also improve and diminish to around 10 knots overnight.


.PREV DISCUSSION... /issued 534 AM CST Fri Dec 8 2017/

..Historic Winter Weather Event Unfolding across Deep South Texas
this Morning...

SHORT TERM (Today through Saturday): The morning commute will likely
be difficult to hazardous across much of the area with slick
roadways and a few icy spots on elevated surfaces and overpasses.
Motorists are urged to slow down, use caution and allow extra time
to reach their destination!

Widespread mixed precipitation continues across much of Deep South
Texas with snow being reported at several observation sites in the
upper Ranchlands of Zapata, Jim Hogg, Brooks and Kenedy counties.
Accumulating snow was reportedly covering the roadways on Highway
281 near Falfurrias earlier this morning with an estimated 1 to 2
inches on the ground. Sleet has continued off and on with light rain
here at NWS Brownsville, but a changeover might come soon as the low-
levels continue to cool.

Winter Storm Warnings continue across the western half of the area
with 1 to 3 inches of total snowfall possible. Further east, Winter
Weather Advisories continue with generally one half of an inch
expected with more of a mix of rain and sleet. A few locations could
see higher amounts if a heavier band or two develops and snowfall
rates increase.

A 500mb trough is located to the west of our area with an upper
level 80 to 90 knot jet streak overhead providing substantial lift
across the area. Moisture generally has not been an issue with a
saturated profile from the surface through the dendritic growth
zone, so frozen precipitation will likely continue through much of
the morning. When the trough axis moves through the area later this
afternoon, precipitation chances will quickly drop off with skies
clearing from west to east this evening. Temperatures will struggle
to reach 50 degrees for daytime highs, which is more than 20 degrees
below normal.

Tonight, strong subsidence and dry air will move into the region
with another very cold night ahead. Clear skies and lightening winds
may drop temperatures to near freezing in a few spots, but
confidence is low on issuing a Freeze Warning at this point.
Saturday, below normal temperatures and mostly sunny skies are
expected with highs in the mid 60s for most locations.

LONG TERM (Saturday Night through Thursday): The forecast period
begins with a 500 mb trough over the east and a 500 mb ridge over
the west. This blocking pattern will continue through the rest of
the weekend into early next week. Surface high pressure will
settle across deep south Texas Sunday and Monday with dry
northwest flow aloft. A cold front is expected to move through the
region on Tuesday. Temperatures will remain mild through much of
the period. High temperatures will slowly recover from the 60s on
Sunday to the mid 70s by Thursday. Below normal low temperatures
are expected Saturday night through Tuesday night with
temperatures becoming near normal by Wednesday night. Rain-free
conditions should prevail through the period.

MARINE (Now through Saturday): Dangerous marine conditions will
continue this morning and early afternoon with strong northwest
winds and very hazardous wave heights across the Gulf waters as an
area of low pressure maintains a tight pressure gradient across the
western Gulf. A Gale Warning has been extended to 3 PM with Small
Craft Advisories likely to follow through Saturday. Conditions will
improve Saturday evening as winds lighten and seas slowly subside.

Saturday Night through Tuesday Night...Much improved winds and seas
are likely Sunday and Monday as high pressure settles across deep
south Texas. Moderate north winds and moderate seas are expected on
Tuesday in the wake of a cold front.


TX...Winter Storm Warning until 9 AM CST this morning for TXZ248>250-

     Wind Chill Advisory until 10 AM CST this morning for TXZ248>257.

     Winter Weather Advisory until 9 AM CST this morning for TXZ251-

     Wind Advisory until noon CST today for TXZ251-256-257.

     Coastal Flood Advisory until noon CST today for TXZ251-256-257.

GM...Gale Warning until 3 PM CST this afternoon for GMZ130-132-135-



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