Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 172352 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
652 PM CDT Mon Apr 17 2017

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


.AVIATION...Scattered strong to severe convection is noted well
north of the TAF sites and slowly propagating east to southeast.
Some of the stronger storms do have 1-2 inch size hail stones
indicated by radar. Probabilities are low but high enough to
mention convection in the 00Z TAF package between 02Z-06Z.
Convection should begin to wane before midnight with areas of rain
and showers lasting  a few hours after midnight. Outside of the
convection MVFR cigs to develop overnight and persist through mid
morning Tuesday. Ceilings to lift to VFR but another round of
convection is probable mid to late afternoon. light to moderate
southeast winds tonight and Tuesday with gusts up to 20 knots


.PREV DISCUSSION... /issued 300 PM CDT Mon Apr 17 2017/

SHORT TERM (Tonight through Tuesday Night):
A somewhat unsettled forecast through the period with the
potential for an MCS/MCV to impact most of the Valley later today
through Tuesday. The main culprit is short wave energy embedded in
otherwise zonal 500 mb flow which carves out a weak 500 mb trough
that slides through South Texas today through Tuesday before
exiting into the Gulf Tuesday night.

Tonight: An MCS/MCV may be in the cards and this time the potential
is farther south. The Sierra Madres may light up down the line with
thunderstorms, and may include areas west of Zapata and Starr as the
short wave rounds the base of the weak 500 mb trough developing over
South Texas. Timing favors 00Z to 03Z just west of the Rio Grande,
easing into at least the upper Valley and ranchlands thereafter,
perhaps having enough strength to reach more population (McAllen) by
midnight or so. Once again, there is the potential for the usual
spring suspects of gusty and damaging winds, large hail in embedded
stronger cells, and local nuisance flooding. SPC assesses areas
adjacent to the river at a marginal risk for severe convection.

Tuesday: Plenty of boundaries and this time just about everywhere.
Surface/low level winds will be disrupted so impossible to say
exactly where the initiation points might be. One thing that does
look likely is some drier air to sneak into the Rio Grande Plains
and have lowered chances out there. Did not go with any heavy
rainfall mention in grids at this point. As with any spring upper
troughs, the potential for clusters of discrete cells that can
produce strong winds or hail well as nuisance flooding
of poor drainage locations with slower moving clusters. High temps
were lowered a category to the lower and  mid 80s.

Tuesday night: Convection may linger late in the day Tues, moving
offshore overnight, with a mid level weakness drifting slowly
offshore. Midlevel ridging over North Central Mexico will begin to
nose northeast over Central Texas. As rain chances taper off from
west to east, the aftermath will be cloudy skies, light east to
southeast winds, patchy light fog, especially across the ranchlands
and brush country, with low temps from the mid 60s to lower 70s.

LONG TERM (Wednesday through Monday): By Wednesday the trough
will be moving offshore, with dry north northwest flow immediately
in its wake. A small chance for showers will remain early in the
afternoon right along the coast, depending on if the seabreeze can
tap any remaining moisture. Capping will strengthen quickly
through the afternoon, so any remaining rain chances decrease
through the day. Ridging remains ahold of Texas Thursday into
Saturday, with dry air aloft holding down the atmosphere. Saturday
night into Sunday the late season cold front sweeps across the
region, being dragged through by a trough passing through the
central plains. With the passage happening overnight, Any
thunderstorm activity will likely not be overly strong, but will
still see a broken line of thunderstorms late night. High pressure
moves in behind the front, leading to a cooler Sunday and Monday.

Now through Tuesday night: Light to moderate southeast winds and
low to moderate seas will prevail with high pressure over the
Gulf. A passing upper disturbance will result in unsettled weather
through the period.

Wednesday through Friday: Weaker high pressure across the northern
Gulf will lead to lighter winds and seas for the latter half of
the week. Winds will be from the southeast 10 to 15 knots each
day, with seas right around 3 feet as the long fetch shortens up
across the western Gulf.




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