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Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 211747 AAC
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1247 PM CDT Tue May 21 2019

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

&&

.AVIATION...MVFR cigs near KBRO become VFR this afternoon as
cumulus disperse with the continued mixing of drier air aloft. VFR
to dominate the remainder of the afternoon and a few hours after
sunset before the stratus layer reforms and spread north and west.
MVFR cigs expected most of the night and into Wednesday morning
before mixing out by Noon Wednesday. South and Southeast wind 
remain strong and gusty with gusts as high as 30 knots at KHRL and
KBRO before diminishing by evening, however gusts to remain around
20 knots much of the night. Windy conditions resume Wednesday with
southeast winds 20-25 knots. 

&&

.PREV DISCUSSION... /issued 958 AM CDT Tue May 21 2019/ 

DISCUSSION...Latest surface observations platforms and WSR-88D
VAD wind profile indicate the pressure gradient across the region
remaining strong this morning. The current VWP showing winds up 
to 52 knots between 2500-4500 feet with some of these stronger
winds mixing to the surface this morning with plenty of mechanical
mixing underway. With this said, a wind advisory has been issued
for the 3 coastal counties through at least 2 pm. The low level 
jet is expected to shift offshore by or shortly after noon as the 
cold front/dry line moves into the far western portions of the CWA
weakening the overall pressure gradient.

PREV DISCUSSION... /issued 607 AM CDT Tue May 21 2019/ 

DISCUSSION...Updated for latest aviation and marine discussions 
below.

AVIATION...VFR conditions will work in from west to east this
morning, with skies likely clearing to the west, including MFE for
this afternoon. HRL and BRO may hold onto a fewer high clouds this
afternoon. MVFR CIGs return late this evening from east to west
and continue into Wednesday morning. Strong southerly winds will
diminish slightly this morning into this afternoon, remaining
breezy to windy across HRL and BRO through this evening and into
tonight. 

MARINE...Have replaced the Gale Warning with a Small Craft
Advisory across Gulf of Mexico waters as previously advertised,
currently in effect through tonight. Winds may diminish this
evening through tonight, with seas expected to stay above SCA 
criteria through Wednesday. Extended the Small Craft Advisory for 
Winds across the Laguna Madre also through tonight, although, this
would depend on winds along the lower Texas coast persisting 
above advisory criteria through the period. 

PREV DISCUSSION... /issued 422 AM CDT Tue May 21 2019/ 

SHORT TERM (Today through Wednesday): Low pressure continues 
across the Plains, keeping SE to SSE winds moderate to strong 
along the lower Texas coast. The dryline works into the western 
counties this afternoon, perhaps as far east as Hidalgo County, 
before retreating back west this evening. The arrival of this 
feature could help boost high temperatures out west, clear skies 
faster, and help to keep stronger winds further east. This will 
also bring a brief break from the muggy conditions, cutting 
humidity values through the afternoon. Heat Index values across 
portions of the low to mid valley will approach 105 degrees today.

Today will likely be the hottest day of the week, at the very 
least rivaling the highs observed on Sunday and Monday, but 
Wednesday may feel more uncomfortable due to the return of higher 
humidity values. This leads the upper valley and western brush 
country areas towards Heat Advisory criteria Wednesday afternoon. 
Heat Index values across the RGV will top 105 degrees, and 
approach 110 degrees near the border in Starr and Zapata counties.

LONG TERM (Wednesday Night through Monday): A series of 500 mb
closed lows will dominate the western portions of the lower 48
states through Monday. At the same time, 500 mb troughs will dig
down over the western Atlantic into the weekend. This will in turn
build a broad and strong ridge axis over much of the southeastern
States and the Gulf of Mexico. This will result in a persistent
hot and rain free pattern over the RGV through Mon. Low level
moisture values will persist throughout the period making for
pretty elevated heat indices each afternoon. However, significant
deep layer moisture will remain absent across the area keeping
pops in the silent 5 to 10 % range. 

Temp and pop guidance from both the ECMWF and the GFS are in very
good agreement through Day 7/8 and run to run consistency is very
steady over the last several days runs. So will go close to a
model blend for highs and lows throughout the period.  

The PGF will remain pretty strong throughout the upcoming long
range period resulting in persistent breezy to windy conditions
into the Memorial Day Weekend.

MARINE (Now through Wednesday): Strong SE winds gradually 
decrease into mid morning, with moderate to strong SE and SSE 
winds continuing through Wednesday, peaking slightly again 
Wednesday afternoon. Gale Warning continues until 7 AM this 
morning, with most observations showing improvement over the past 
couple of hours. A Small Craft Advisory will follow and likely 
continue through Wednesday. A Small Craft Advisory for Winds will 
be extended across the Laguna Madre into Wednesday as well. 

Wednesday Night through Saturday Night: Persistent surface 
ridging over the Gulf of Mex will interact with a steady
progression of surface low pressure systems moving across the
central Plains States to maintain SCEC/SCA conditions over much 
of the lower TX marine areas through Sat Night. The strongest PGF
will most likely occur around Wed/Thurs with a little lower winds
and seas expected Sat/Sat Night. 

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory until 2 PM CDT this afternoon for TXZ251-254>257-
     351.

GM...Small Craft Advisory for winds until 7 AM CDT Wednesday for 
     GMZ130-132-135.

     Small Craft Advisory until 7 AM CDT Wednesday for GMZ150-155-170-
     175.

&&

$$

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