Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 231825 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1225 PM CST Tue Jan 23 2018

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


.AVIATION...IR Satl imagery shows high and mid level cld cover
advecting over the RGV today with a light to moderate NE surface
flow prevailing. The 12Z BRO sounding shows that the atms over the
region is pretty dry with the exception of the 700-850 mb layer
which has some better moisture values. The deeper layer moisture
values will remain pretty low throughout the first half of the
upcoming TAF period allowing for VFR conditions to prevail. The
deeper layer moisture will then start increasing over the RGV from
the south as a 500 mb closed low approaches the region from the
west. This will allow the ceilings to lower later in the forecast
period likely resulting in more MVFR conditions during the latter
half of the TAF period.


.PREV DISCUSSION... /issued 556 AM CST Tue Jan 23 2018/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...High pressure over North Texas will maintain northeast
winds with VFR conditions likely through the next 24 hours. Middle
and lower level clouds will increase Tuesday night into Friday
morning with a few showers possible across the lower Rio Grande

PREV DISCUSSION... /issued 439 AM CST Tue Jan 23 2018/

SHORT TERM (Now through Wednesday): Upper level Cirrus clouds
continue to stream northeastward over South Texas this morning with
southwest flow bringing much drier air below it in the mid levels.
At the surface, nearly stationary high pressure over North Texas
will maintain northeast flow through the short term period.
Temperatures tonight have dropped into the 40s across most areas
with the Upper Valley falling into the 30s due to dry air and light
winds. This afternoon temperatures will be a few degrees cooler than
yesterday, with highs near normal in the low 70s, with northerly
flow and 1000-500mb thicknesses falling a couple decameters. Rain-
free conditions are expected today as mean RH values range from 20
to 30% below 700mb and from 5 to 10% in the mid levels. Moisture
will increase from the south late tonight into Wednesday morning,
bringing increasing cloud cover and rain chances across mainly the
southeastern corner of the area, including the lower Rio Grande
Valley and southern coastal waters.

LONG TERM (Wednesday Night through Monday): The most active day
during the long term portion of the forecast is anticipated to be
on Saturday, as the approach of a weak cold front from the north
combines with the passage of a 500 mb trough to produce scattered
convection. Up until that time, isolated precipitation is
anticipated, as a closed 500 mb low initially over northwest
Mexico slowly moves east-northeast across the Desert Southwest
and the Lone Star State. The persistent rain chances, coupled with
significant cloud cover overhead through a majority of the
period, will produce temperatures at near normal levels throughout
the entire forecast period.

MARINE (Now through Wednesday): Surface high pressure over North
Texas will maintain moderate northeast winds through the period with
moderate seas ranging from 4 to 5 feet. Rain chances will increase
Tuesday night into early Wednesday for the southern coastal waters
as moisture surges northward.

Wednesday Night through Monday: Moderate winds and seas will
prevail along the Lower Texas Coast, and these conditions will
likely create Small Craft Exercise Caution seas for the Gulf of
Mexico waters from 0 to 20 and/or 0 to 60 nautical miles offshore
Wednesday night through Saturday night. The passage of a cold
front during the weekend will produce stronger winds and rougher
seas, with Small Craft Advisories more likely Sunday and Monday.




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