Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 182356
Area Forecast Discussion
National Weather Service BROWNSVILLE TX
656 PM CDT WED MAY 18 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Atmosphere has (at least temporarily) stabilized in
the wake of severe thunderstorm complex that moved across the
northern counties this afternoon. Can`t see convective features immediately
upstream in radar or satellite imagery so will delete thunderstorm
mention from TAF`s and go with VFR conditions for the next
Short-term guidance (such as NAM and HRRR) suggesting that
aviation conditions may begin to deteriorate again around 06Z as
an upper-level impulse approaches from the west. MVFR ceiling and
visibilities will be possible near thundershowers. Model guidance
seems to be zeroing in on Thursday morning for biggest rain threat
at the terminals, so will forecast VCTS prevailing after 09-10Z,
but of course convective details will need to be updated. After
the upper impulse passes around 18Z tomorrow, conditions may
trend back to VFR for the afternoon.
.PREV DISCUSSION... /issued 321 PM CDT WED MAY 18 2016/
SHORT TERM (Tonight through Thursday Night):A late season cold
front is located over the northern Ranchlands with a bow echo
anchored along the boundary moving steadily east over Jim Hogg
and Northern Starr counties. GFS as well as the HRRR shows a
strong vort max moving across South Central Texas approaching the
Lower TX coast through this evening. This disturbance should
maintain the integrity of this cell as well allow for additional
cell development the rest of the afternoon. GFS and again the HRRR
show another strong disturbance moving out of Mexico into the Mid
and Lower Valley this evening with possibility of another round of
thunderstorms. The ECMWF shows yet another disturbance moving
across the RGV Thursday. The combination of the front abundant
deepening moisture, PWATs 1.8 to 2+ inches, and the disturbances
will keep a small threat of severe weather with a more substantial
transition to a heavy rain event with training of heavy showers
and thunderstorms anticipated along and south of the cold front.
WPC has the western half of the CWA under an slight risk of
excessive rainfall outlook which matches up well with our thinking
locally. QPF values on the latest GFS and ECMWF have increased as
well with each of its distinct disturbances. Have decided to issue
a Flash Flood Watch for our entire CWA from 7pm this evening until
7 pm Thursday. Temperatures will be subject to the rainfall and
will maintain current lows in the 70s and but lower Thursday highs
in the 80`s which might have to be lowered another category.
LONG TERM (Friday through Wednesday): The upper trough finally
moves east of Texas Friday but trails a cold front into the
region. residual moisture will combine with the low level
convergence along the front to generate another round of showers
and thunderstorms Friday. High pressure ridge builds over Texas
between deep troughs along both the West and East U.S coasts.
Subsidence under the ridge should work on slowly drying out our
atmosphere. This will result in lower rain chances and raised
temperatures this weekend into early next week.
MARINE: tonight through Monday...A weak stationary front to
remain north or lie across the northern coastal waters through
Friday before dissipating this weekend. light to occasional
moderate easterly winds and a low sea to persist. a slightly
stronger gradient this weekend and early next week will allow for
moderate southeast winds and slightly higher seas. No advisories
are anticipated at this time. showers and thunderstorms to
impact the coastal waters at times through Friday with isolated
activity on Saturday.
TX...Flash Flood Watch through Thursday evening for TXZ248>257.
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