Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 182310 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
610 PM CDT Sun Mar 18 2018

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


.AVIATION...Overnight, MVRF and IFR cigs, albeit thin layered,
will develop under a strong low level cap evident on the observed
and forecast soundings. Patchy light fog will also be in the mix.
An isolated shower will be possible Monday during the day as a
weak front moves through, with light northeast winds arriving by
late afternoon, and with clearing skies as dew points decrease in
the drier air mass.


.PREV DISCUSSION... /issued 308 PM CDT Sun Mar 18 2018/

SHORT TERM (Now through Monday night): Satellite imagery showed low
clouds from this morning burned off from west to east in a pattern
very similar to Saturday afternoon. Skies were mostly sunny across
the forecast area with partly to mostly cloudy conditions hanging
over the extreme southeast corner of the forecast area. Will see low
clouds redevelop from east to west over the lower and mid
valley after midnight tonight, but not much going on beyond that.

For Monday, a modest cold front will move through the forecast area
mainly in the morning bringing northwesterly breezes and a
significant amount of dry air. Dew points look to fall into the
mid/upper 20s out west with dew points getting knocked down into
the mid 50s to lower 60s along the coast. The airmass will
actually heat up due to downsloping effects of the northwesterly
flow with highs reaching into the lower to mid 90s in most areas,
except over the southwest portion of the forecast area where temps
could jump into the upper 90s. There is a slight chance of
showers over northern Kenedy County with the passage of the front
where deeper moisture will still be pooled in connection with the
front. As we move into Monday afternoon/night, skies will clear
with northwesterly breezes continuing and low temperatures will
fall into the lower 50s over the north central portion of the
forecast area with lower 60s over the southeast portion of the

LONG TERM (Tuesday through Sunday): Mid-level troughing across
the Southeast will continue through much of the long term period
with ridging building from west to east into next weekend. At the
surface, a surface low will also move into the Southeast,
maintaining northeast flow across South Texas in the wake of a
trailing cold front. The main impacts through mid week will be
elevated fire weather concerns with very dry air keeping dew
points in the mid 20s along Interstate 69-E and mid teens out west
Tuesday afternoon. This will continue into Wednesday before winds
shift to the ESE and bring moisture back across the area. By
Thursday and Friday, another storm system will develop in the
Plains, increasing southeast winds to possibly Wind Advisory
criteria. MOS guidance is already indicating around 25 to 30 mph
sustained winds in the Lower Valley with gusts likely to 30 to 40
mph Friday and Saturday.

Rain chances are near zero each day as very dry air remains across
the region. If we see any shower activity, the best chance will be
Friday into Saturday, but with RH values under 50% below 850mb
and under 20% above 850mb, not expecting much. Temperatures will
be slightly cooler on Tuesday before increasing each day through
the end of the week. With model guidance persistently under doing
daily highs and the synoptic pattern looking particularly warm,
increased values well above MOS guidance for the second half of
the week. Would not be surprised to set a few records, especially
in the McAllen area where highs could reach around 100F again into
the weekend.

MARINE (Now through Monday night): Little change in marine
conditions from 24 hours ago with nearly calm winds and 3-foot
waves at buoy 20. Modest seas to prevail through the period. Weak
south winds tonight become northerly Monday as a weak cold front
moves across the waters. Winds variable in direction Monday night
in the wave of the front, but generally become northerly again
toward daybreak Tuesday morning as a surge of high pressure moves
southward across the waters.

Tuesday through Friday: A reinforcing shot of high pressure
Tuesday afternoon will bring gusty north winds across the coastal
waters through the evening. Small Craft Advisories will be
possible as winds reach 20 knots and seas across Gulf waters
briefly build to 7 feet well offshore. Winds veer to the east on
Wednesday and increase out of the southeast Thursday into the
weekend. Small Craft Advisories will be likely on Friday with seas
building back to 6 to 8 feet.

FIRE WEATHER (Now through Monday night): Still anticipating
Monday afternoon humidities to fall into the 10 to 15 percent
range from western Hidalgo and much of Brooks County westward
through the Rio Grande Plains. The longest duration and lowest
humidities should be seen in Starr, Jim Hogg, and Zapata Counties.
Low humidities combined with sufficient 20-foot winds will lead
to the potential for erratic/explosive fire development. Fire
Weather Watch still on track for Hidalgo/Brooks westward Monday

Tuesday and Wednesday: Dew points in the mid 20s across the
coastal counties and teens out west on Tuesday will lead to
another elevated fire weather day. 20-foot winds will likely be
below the criterion for any Red Flag Warnings, but winds may
increase enough to cause some issues if any fires manage to
develop. On Wednesday, moisture will increase as surface winds
shift to the east, but an elevated fire weather threat may
continue for a period in the western counties of Zapata, Jim Hogg
and Starr.


TX...Fire Weather Watch from Monday afternoon through Monday evening
     for TXZ248>250-252-253.



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