Area Forecast Discussion
Issued by NWS Brownsville, TX

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112
FXUS64 KBRO 302347 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
647 PM CDT Sun Apr 30 2017

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

&&

.AVIATION...Winds will become E to SE through the next few hours
with speeds decreaing. Clear skies and little low level moisture
will keep VFR conditions in place through the period.


&&

.PREV DISCUSSION... /issued 234 PM CDT Sun Apr 30 2017/

Short Term (Tonight through Monday night): 500mb low across the
central and southern plains this afternoon will move northeast
across the midwestern United States tonight. West to northwest
flow across the state will provide subsidence across south Texas
tonight into Monday. Temperatures tonight will be a challenge as
winds diminish tonight and veer to the east. The NAM and GFS MOS
have a fairly large spread for temperatures tonight and Monday.
Will go with a blend of MOS guidance for lows tonight but lean
towards the high end of the guidance Monday as south to southeast
winds will prevail across the CWA Mon afternoon with not much in
the way of cloud cover. Moisture will return across the area late
Mon night and temperatures will be warmer Mon night compared to
tonight with cloud cover returning.

LONG TERM (Tuesday through Sunday): After a lull in significant
weather early in the week, attention will focus on the ramp up to a
Wednesday night cold front that will bring a chance of showers and
thunderstorms to much of the forecast area.

Tuesday and Wednesday will reflect a warming trend as southeast
winds become reestablished and low level moisture increases. One
outcome will be afternoon sea breeze development, as well as morning
streamer and coastal shower potential. Moderate strength showers
will be possible, but a persistent cap should preclude deeper
development. This activity will be robust enough to include in the
forecast. High temperatures on Wednesday will get well into the 90s
inland, pushing heat index values to near or slightly above the
century mark.

Pwat values will surmount an inch on Tuesday and will keep climbing.
By Wednesday, forecast values will be above the 90% moving average.
The main storm system will be tracking across ArkLaTx late Wed, with
a trailing front down through Texas. There should be a small window
of enhanced instability Wed night as the front arrives and blasts
away the cap, leaving steep lapse rates and favorable buoyancy. The
base of an associated mid level trough axis will be overhead or
slightly upstream as well. The front will move through quickly, from
late evening over the Upper Valley, to midnight or early morning
Thurs, and a few stronger to marginally severe cells appear possible
at this point, with damaging wind and small hail potential something
to consider.

Once the front clears the area, fair weather will settle in for
the remainder of the long term, with mostly clear skies and near
normal temperatures. A peek at fire weather parameters indicates
some enhancement with moderate 20 feet winds, and relative
humidity values in the 20s Thursday afternoon, but below critical
thresholds. Post front winds will remain northeast through around
Friday as high pressure spreads over the area, before swinging to
southeast again over the weekend.

MARINE:
Tonight through Monday night: Seas were near 9 feet with north to
northwest winds near 18 knots at buoy020 this afternoon. Moderate
to strong northeast winds will diminish and veer to the east
tonight as surface high pressure across the northwest Gulf of
Mexico moves eastward but seas will remain elevated through this
evening. Will extend SCA for the offshore waters through 12
midnight as a result. Winds will continue to diminish Monday and
veer to the southeast as the pressure gradient continues to weaken
across the western Gulf. Light southeast winds will prevail
across the lower Texas coast before the pressure gradient tightens
Mon night as low pressure develops across west TX. Moderate
southeast winds should prevail across the coastal waters Mon
night.

Tuesday through Friday...Upper moderate southeast winds and upper
moderate seas will prevail Tuesday and Wednesday as high pressure
continues across the Gulf. Winds and seas will be on the increase
Wednesday, however, due to pressure falls upstream, with low end
small craft advisory conditions possible on the Gulf Wednesday
night. A Thurs. morning front will generate strong north winds and
elevated seas for the day, with small craft advisory conditions.
Diminishing north winds will continue Thursday night into Friday
as conditions slowly improve, possibly shifting directionally to
east late as high pressure spreads over the area.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until midnight CDT tonight for GMZ150-155-
     170-175.

&&

$$

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