Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 182334 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
534 PM CST Sun Feb 18 2018

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

&&

.AVIATION...Breezy southeast winds and mostly clear skies prevail
across deep south Texas early this evening. Winds will gradually
diminish to around 15 knots later this evening and overnight. Low
stratus and patchy fog will develop later tonight. MVFR to IFR
conditions are expected at all RGV airports overnight due to
patchy fog and low ceilings. VFR conditions expected by the mid
to late morning as southeast to south winds increase. Gusts of
around 30 knots will be possible in the late morning and
afternoon.

&&

.PREV DISCUSSION... /issued 302 PM CST Sun Feb 18 2018/

SHORT TERM (Tonight through Monday Night): The 500 mb trough
axis will be digging south and east across the western portion of
the lower 48 states throughout the short term period. Meanwhile to
our east 500 mb ridging will build over the southeastern states,
Gulf states and the Gulf of Mexico through tomorrow night. As the
western trough digs south and east, the low pressure system
developing over the central plains states will increase the PGF
over the RGV boosting the surface winds today and Mon. Have posted
a wind advisory this afternoon for Willacy, Cameron and Hidalgo
Counties until 7 pm this evening. Another round of Wind Advisories
will be likely again for Mon for much of the RGV.

The persistent WAA due to the southerly low level flow combined with the
returning sunshine in the late morning and afternoon hours will warm the
temps up quickly for Mon. So will go on the warm side of guidance through
tomorrow night.

The deep layer moisture advection ahead of this digging 500 mb trough will
remain confined generally to the north and west of Deep South TX. So will
maintain only silent 10 % pops until tomorrow night. Will then maintain
some 20 % pops across the far western counties as the moisture advection
gets a little closer to the area. Otherwise a generally dry forecast will
prevail throughout the short term.

Overall confidence in the short term period remains above average.

LONG TERM (Tuesday through Sunday): Deep south Texas will
continue to feature a south to southwesterly wind regime aloft
during the long term as a longwave 500 mb trough remains situated
over the western CONUS and a 500 mb ridge remains to our east.
Rain and thunderstorms will blossom on Tuesday across much of
central Texas out ahead of an advancing cold front and the
positioning of a dryline across west-central portions of the
state. Our area will feature slight chances for showers and
thunderstorms on Tuesday thanks to low-level moisture pooling into
the region from continued southeasterly onshore surface winds.

The chances for rain and convection will then increase as the
frontal boundary drops southward into our area for Wednesday into
Thursday of this week. Question still remains on how far south the
front will drop before stalling. Current thinking is for the
front to stall across the northern half of our CWA. This will lead
to quite a temperature gradient across the area on Thursday with
cooler air across the northern ranchlands and warmer conditions
across the valley. The frontal boundary will then lift northward
late in the week. However, low-level moisture across the region
will remain enough for a continued slight chance of rain showers
and thunderstorms.

Another cold front will move into Texas for the upcoming weekend.
This front looks to behave similar to the previous front where it
will lead to increased chances for rain and convection but may try
to stall across deep south Texas. Exact location of where the
front will stall remains up in the air.

MARINE: The marine fog will again be the main issue for the
short term period as the WAA continues flowing over the cooler Bay
and Gulf water. Surface obs and web cams indicate that the dense
fog has dissipated for moment due to the increased low level
mixing over the region. However, as the surface flow decreases
over the marine locations later tonight and early Mon morning will
likely allow for more dense fog overnight. However will not post
a Marine Dense Fog Advisory at this time in order to see how the
fog progresses later tonight. The cooler Bay and Gulf water temps
will tend to hold down the stronger S-SE low level flow. However
some SCEC conditions will be possible this early evening for the
Bay waters.

(Tuesday through Sunday): Moderate winds and seas will continue
through mid to late week as a cold frontal boundary moves
southward into the region. At this point, low end Small Craft
Advisories can`t be ruled out for the first half of the long term.
Another cold front is poised to move through the region later this
weekend. This may help increase winds and seas a bit, but at this
point seems to be just below SCA thresholds.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory until 7 PM CST this evening for TXZ253>257.

GM...None.
&&

$$

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

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