Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 192352
AFDBRO

Area Forecast Discussion
National Weather Service BROWNSVILLE TX
652 PM CDT THU MAY 19 2016

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

&&

.AVIATION...Main forecast challenge is timing of NE-SW oriented
convective line currently moving through Cameron County and
associated impacts on terminals. Per radar trends and HRRR
guidance, will drop mention of thunder at MFE beginning at 00Z.
Activity should clear HRL by around 01Z...and BRO by 03Z. Will
keep mention of VCSH for a few hours beyond passage of line of
storms but CIGS should be predominantly VFR after passage until
around 06Z.

Didn`t have a chance to closely re-evaluate late overnight period
so will retain IFR CIGs at all 3 terminals from 06-12Z with some
patchy mist...though confidence not especially high.  MVFR
ceilings should return, at any rate, after sunrise Friday. Mainly
VFR expected tomorrow afternoon but will show probabilities for
thunder at terminals as front will still be in the area with
sufficient low-level moisture for at least isolated
thunderstorms.

&&

.PREV DISCUSSION... /issued 245 PM CDT THU MAY 19 2016/

SHORT TERM (Tonight through Friday Night): Upper trough centered
over SE CO and NE NM will be lifting Northeast across the Central
Plains during the short term period. As it progresses
Eastward...the Southeast flow across S Central TX has strengthen
lifting the stationary front currently close to Laredo extending
northeast towards the northwest Gulf Coast. There is enough low
level waa/moisture transport for some convection to initiate along
the stationary frontal boundary. Currently, isolated to scattered
showers are starting to develop over northern Hidalgo, Brooks and
Kenedy Counties producing brief moderate rain showers while moving
North to NE. Further north, a line of thunderstorms will
eventually move across the cwa. This convection will increment
across the cwa through out the day with the potential for severe
thunderstorms later this afternoon into tonight. SPC has lowered
the threat for most of Deep South Texas under a Marginal and a
Slight Risk near Kenedy County. The storms could become severe
with the potential to produce large hail, damaging winds, and
flash flooding, expected to move into Deep South TX and the Rio
Grande Valley. Flash Flood Watch has been extended through
1 am as the line of cells is slowly moving eastward. Have
included these weather threats in the forthcoming official
forecast. Localized heavy rainfall is possible with any
thunderstorm through tonight could lead to minor flooding.
Rainfall amounts will range between a half an inch with higher
amounts of 1 to 2 inches are possible mainly over the Northern
counties.

The front will begin to lift Northeast and enhance another
cluster of convection early Friday through Friday night with a
weak easterly flow across the area. Lingering moisture over the
region east of the Sierra Madre will enhance showers and
thunderstorms along the mountains and the western counties through
the night. High temperatures will be in the mid to upper 80s
Friday and with more sunshine expected Saturday temps reach the
90s mainly out west and mid 80s neat the coast. Low temperatures
will be ranging between the mid to upper 70s.

LONG TERM (Saturday through Thursday):The long term starts off
with a 500mb ridge building over Texas behind the departing upper
trough and a deepening upstream upper low across the Intermountain
West. The ridge holds strong through Tuesday then begins to
flatten as it gets shoved eastward as the western upper low opens
up into a trough.

residual low level moisture combining with daytime heating may set
off isolated showers and thunderstorms over the weekend but coverage
will be very limited as the mid level dry air deepens as subsidence
increases with the building ridge. Dry conditions to prevail Monday
through Wednesday at this point in time with ridge axis hanging over
Deep South Texas. The ridge axis moves begins to move east late next
week with southwest flow increasing with the low probability of
our next chance of seeing rain chances increase.

Temperatures at the surface and at 850mb increase as the upper ridge
strengthens. 850mb temperatures by next Wed/Thu are approaching 25C.
Guidance from the GFS and ECMWF although in good agreement would
believe we could see daytime maxes exceeding 100 degrees across in
the Rio Grande Plains and upper 90s to 100 degree in the mid and
upper Valley. Overnight lows remain extremely warm with mid to
upper 70s through the period.

MARINE: Now through Friday night, Gradient will be weak
through the period keeping low to moderate seas across the Gulf
Waters. East to Southeast flow will be in place for the period
with strong thunderstorms late this afternoon through Friday.

Saturday through TUESDAY...moderate onshore flow and a low
seas is expected this weekend with a gradual increase in southeast
winds next week as the pressure gradient strengthens. surface high
pressure strengthens across the Gulf of Mexico by the middle of next
week with an upstream upper trough approaching the 4 corners area.
the thermal gradient to strengthen between the cooler Gulf waters
and inland areas allow for breezy to strong southerly flow to
develop at times. Periods of exercise caution to short duration
small craft advisory conditions may develop.

&&

.BRO Watches/Warnings/Advisories...
TX...Flash Flood Watch until 1 AM CDT Friday for TXZ248>257.

GM...None.
&&

$$

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