Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 172249 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
549 PM CDT Sat Mar 17 2018

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


.AVIATION...MAV guidance is still hinting at patchy fog for the
aerodromes tonight, closer to dawn, along with a drop to IFR
ceilings after midnight, not really lifting to MVFR or better
until mid to late Sunday morning. A time height profile supports
the shallow, very high RH layer overnight. The NAM guidance is
not as aggressive as the MAV, but the signal is present.


.PREV DISCUSSION... /issued 254 PM CDT Sat Mar 17 2018/

SHORT TERM (Now through Sunday night): Modest low level
southerly flow combined with sufficient moisture is bringing
scattered to broken stratocu to the eastern third of the forecast
area, while skies are mostly sunny over the western two-thirds.
Will see a little more dissipation of the clouds over the east
this afternoon and evening. However, clouds will begin to
redevelop and spread westward overnight. Additionally, will see
patchy fog develop over the eastern half of the forecast area,
including South Padre Island.

For Sunday, a very weak upper level shortwave trough and associated
surface front will move across the forecast area. Increased
moisture, cloud cover, and weak dynamics will allow for some
isolated showers to develop, mainly over the northern tier of
counties, Sunday afternoon. Skies will become mostly sunny out west
though skies over the east look to remain at least partly, if not
mostly cloudy, all day. High temperatures look to be similar to
highs that will be reached this afternoon with lower 80s at the
coast to the mid 90s out west. Low clouds with patchy fog will
redevelop again mainly over the east half of the forecast area
Sunday night into early Monday.

LONG TERM (Monday through Saturday): Models are in good agreement
on the position of a deep 500mb low moving eastward through the
Ohio River Valley Monday into Tuesday with a surface low bringing
a cold front into South Texas on Monday. Moisture will be very
limited with a strong capping inversion just above the surface,
which will considerably limit precipitation. Have kept a slight
chance in for the eastern half of the area as a sharp dew point
gradient behind the front may be enough to spark a shower or
storm off briefly. Behind the front, very dry air will quickly
move in with crashing dew points into the 30s and even 20s out
west. The main concern will be the potential for elevated fire
weather conditions, but winds may not reach the threshold for a
Red Flag Warning as 20-foot winds will range from 10 to 15 mph. In
the afternoon no relief from the heat through the region with
highs still reaching the 90s in many areas.

Slightly cooler weather is expected Tuesday and Wednesday with
highs in the 80s, though still above normal for this time of year.
Very dry air from the surface through the upper levels will
suppress any rain chances with clouds struggling to develop at
all. Southeast flow at the surface will return as high pressure
moves off eastward, bringing some moisture back to the near-surface.
A strong pressure gradient will develop by the end of the week
with a deep low developing in the Plains, leading to breezy to
windy conditions. Model guidance indicates possible Windy
Advisory criteria, especially along the coastal counties.

MARINE (Now through Sunday night): The pressure gradient remains
slack over the northwest Gulf with southeast winds at Buoy 20
less than 10 knots. Modest winds/seas to prevail through the
period due to little change in the overall pattern.

Monday through Thursday: A cold front will move through the
coastal waters late Monday morning with winds shifting to the
north at 5 to 10 knots. Low seas will continue through early
Tuesday with winds quickly increasing in the afternoon as
reinforcing shot of high pressure moves southeast into East Texas.
Small Craft Advisories may be needed through Tuesday evening.
Conditions will improve on Wednesday with southeast flow bringing
increasing winds and building seas back on Thursday.




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