Area Forecast Discussion
Issued by NWS Brownsville, TX

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761
FXUS64 KBRO 241138
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
538 AM CST Fri Feb 24 2017

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

&&

.AVIATION...A dry cold front will sweep through the Mid to Lower
RGV between 15Z to 18Z today. Winds will veer from south to
southwest later this morning ahead of the front...with winds
increasing from the northwest as it passes. Winds will veer to the
north to northeast late in the day...with speeds dropping off
near sunset. VFR conditions will prevail through the period.

&&

.PREV DISCUSSION... /issued 432 AM CST Fri Feb 24 2017/

SHORT TERM (Today through Saturday): After numerous record-breaking
highs across the region on Thursday...some relief is in sight as a
dry cold front sweeps into the area later this morning. And by
relief...I mean that highs across the River Valley areas will be
only 10 to 15 degrees above normal instead of the near 20 to 25
degrees above normal that we have been running.

The front will begin moving into Zapata County just before
sunrise...and will push southeast through the Lower RGV around noon.
Although the temps today will be lower...northwest winds will
increase behind the cold front later this morning...especially
across areas west of I-69C. Models suggest 850mb winds near 30-35
knots...and with mixing down...winds will become rather gusty today.
Although there has been some moisture return farther west into the
Deep South Texas given some fog formation over the Northern
Ranchlands...extremely dry air aloft will filter down today and the
front will bring an additional surge of lower dewpoints. As
such...Red Flag Warning criteria will be met across much of the CWA
this afternoon. Have decided to include all counties except for
Coastal Willacy and Coastal Cameron Counties.

Winds will decrease around sunset and switch from the north-
northwest back the northeast overnight. High pressure will settle
across Northern Texas with easterly flow and moisture making a
return. Highs temps on Saturday will be noticeably cooler...with
humidity values noticeably higher.

LONG TERM (Saturday Night through Thursday): A zonal 500 mb
pattern will prevail over the RGV as a series of short waves move
across the northern states. A series of short waves will carve out
a broad and deep trough axis over the western states through Tues.
This will in turn build a broad but shallow ridge axis over the
Gulf of Mex early next week. As the western trough axis shifts
eastwards a cold front will be pushed southwards eventually
moving through the RGV on Wed. Overall moisture values across Deep
South TX remain on the low side ahead of this next trough axis
and the cold front associated with it. Enough moisture may pool
over the eastern counties and offshore late in this extended
forecast period to generate some 20-30% pops for Wed and Thurs.

The zonal/weak ridging pattern indicated in the 500 mb field
through early next week will maintain temps well above climo for
late Feb. CAA in the wake of the fropa Wed will then drop the
temps down close to or just below climo for the latter half of
next week.

The longer range models show decent agreement in the 500 mb fields
through Day 7 but diffences do show up. The GFS is a bit faster in
the timing of the fropa Wed versus the ECMWF. The GFS also shows a
little stronger CAA over the RGV starting next Wed. The GFS is
also wetter after the fropa versus the ECMWF. Ahead of the front
the ECMWF maintains its usual warm bias over the GFS.

Will opt for the ECMWF high temps before the fropa with the min
temps a blend of the GFS/ECMWF. After the fropa will go for a
general 50/50 blend of the GFS/ECMWF for both temps and pops from
Wed through Thurs. Overall confidence in the longer term forecast
wording is generally above average due to the decent model
agreement before the fropa with the forecast confidence dropping a
bit after the front as the GFS and ECMWF output differs more.

MARINE (Now through Saturday): Observations at Buoy 42020 early
this morning are showing higher SSE winds around of 20 to 23
knots...with higher gusts to 25 knots. Seas have come up to 5 feet.
As such...have issued a SCA until 9AM for winds and seas for the 20-
60 NM Gulf waters.  The pressure gradient will weaken ahead of a dry
cold front which will move through the Lower Texas Coastal Waters by
early afternoon. Winds will become light southwest to northwest in
the afternoon...with light northerly winds this evening. Seas will
also subside. Surface high pressure will build across the Northern
Gulf on overnight with moderate northeast winds over the offshore
Gulf waters...and Small Craft Should Exercise Caution conditions
will be possible through the day Saturday for winds.

Saturday Night through Tuesday Night...A moderate south to
southeast low level flow will prevail for the weekend into early
next week as surface ridging prevails over the Gulf of Mex. This
may result in some marginal SCEC/SCA conditions along the lower TX
coastline into early next week.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Red Flag Warning from noon today to 6 PM CST this evening for
     TXZ248>255.

GM...Small Craft Advisory until 9 AM CST this morning for GMZ170-175.

&&

$$

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