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Area Forecast Discussion (AFD)

Issued by Brownsville/Rio Grande Valley, TX (BRO)

FXUS64 KBRO 250930

Area Forecast Discussion
National Weather Service Brownsville TX
430 AM CDT Mon Sep 25 2017

.SHORT TERM (Now through Tuesday): Deep South Texas will remain 
between a large scale mid/upper level trough over the western half 
of the U.S. and a mid/upper level low over the northern Gulf of 
Mexico with weak mid-level ridging overhead through the period. 
Moist southeast flow in the low levels and southwest flow aloft will 
allow deep tropical moisture to increase across the region through 
the period. BRO sounding from Sunday evening showed a precipitable 
water value of 1.73 inches which is close to the recent GOES-16 
value of 1.80 inches. Brownsville radar currently shows a few 
streamer showers moving northwest across the lower Texas coastal 
waters this morning.

The western 500mb trough will build eastward today into Tuesday with 
deep layer moisture increasing through the period. Isolated to 
scattered showers and thunderstorms expected today into Tuesday. The 
main issue in the short term will be the amount of cloud cover which 
may impact rain chances and high temperatures for today and Tuesday. 
The best rain chances will be across Zapata, Starr and Jim Hogg 
counties due to higher QPF and the close proximity to the 500mb 
trough. Made only minor adjustments to the inherited temperatures, 
cloudiness and pops. Will lean towards of a blend of the 
MET/MAV/ECMWF for pops.

.LONG TERM (Tuesday Night through Sunday): Isolated to scattered
showers and thunderstorms will dominate through the entire long
term forecast period. The anticipated weather will be the result
of persistent 500 mb troughiness over the Desert Southwest,
precipitable water values generally between 2 and 2.25 inches
within Deep South Texas and the Rio Grande Valley, and a weak cold
front that will drop through most of the Lone Star State. With the
increased rain chances and expected significant cloud cover,
daytime high and overnight low temperatures will finally range at
near to slightly above normal levels. 

.MARINE (Now through Tuesday): Surface high pressure across the 
southeastern United States will remain in control through the 
period. Mariners can expected favorable marine conditions as light 
to moderate southeast winds and low seas continue. Isolated to 
scattered showers and thunderstorms will prevail through Tuesday.

Tuesday Night through Sunday: Generally moderate winds and seas
are expected along the Lower Texas Coast through the period with
surface high pressure in control. Small Craft Exercise Caution and
Small Craft Advisory are not anticipated to be needed. 

BAYVIEW/PORT ISABEL  90  80  91  79 /  30  20  30  30 
BROWNSVILLE          92  79  91  78 /  30  20  30  30 
HARLINGEN            94  78  93  77 /  30  20  30  30 
MCALLEN              96  79  95  78 /  30  20  40  30 
RIO GRANDE CITY      97  78  95  77 /  40  30  50  30 
SOUTH PADRE ISLAND   88  80  88  79 /  30  20  30  20 



This product is also available on the web at:

Short term...Caceres-63
Long term...Tomaselli-66