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Area Forecast Discussion (AFD)

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

FXUS64 KBRO 221056

Area Forecast Discussion
National Weather Service Brownsville TX
456 AM CST Tue Jan 22 2019

.SHORT TERM (Now through Wednesday): The next trough has dropped 
into the SW US and will deepen as it settles into the Plains through 
West Texas and into Northern Mexico today. The pressure gradient 
continues to strengthen, allowing stronger southerly winds to kick 
up by late this morning and continue into this evening. Model 
soundings and early morning VAD wind profiles have consistently 
shown 40+ knot winds above 2k feet. With a very warm day and plenty 
of mixing expected, have hoisted a Wind Advisory for Cameron and 
Willacy counties, extending north along Coastal Kenedy County. Gusty 
winds are expected into Hidalgo County, likely less frequent and 
generally just under advisory criteria. 

A strong cold front sweeps across South Texas toward the Gulf coast 
overnight into Wednesday morning. Winds drop off before shifting 
northerly and increasing behind the front into Wednesday afternoon. 
The best chance of rain occurs with the front, mainly before 
sunrise. Model soundings show PWAT values near 1.5 inches across the 
northeast with the frontal passage, allowing light to moderate rain 
showers across the northern ranchlands dipping south along the 
coast. Much of the rest of the CWA will remain dry, continuing fire 
weather concerns behind the front as winds pick up mid to late 
morning. Ongoing convection with the front is likely the best chance 
for any thunder in our CWA with model soundings unfavorable for new 
convective development. Have left isolated wording in, keeping it 
mainly offshore. 

Temperatures today with increased southerly winds should top off a 
few degrees warmer than yesterday, into the upper 70s and low 80s, 
well above normal for late January. Overnight, near normal lows 
return with temperatures falling to the upper 40s and low 50s thanks 
to lighter winds. Only slight warming is expected on Wednesday, with 
strong northerly flow and increased cloud cover early keeping highs 
generally in the mid to upper 50s. Recent model trends have been 
warmer with each run, and a few locations far south and west may 
reach into the low 60s. Fire weather concerns for Wednesday remain 
elevated and will continue to be monitored, especially if stronger 
winds stick around and temperatures warm further. 

LONG TERM (Wednesday night through Monday): The tale of the long 
term and beyond will be an east Pacific mid level ridge positioned 
roughly along the western United States, and multiple short wave 
troughs plunging south to the east of the ridge and over the western 
CONUS, with underlying polar outbreaks. This will tend to keep 
temperatures cooler than normal, barely able to warm to near normal 
before the next system arrives. Initially, a Wednesday cold front 
will leave colder weather over the CWA Wednesday night as high 
pressure settles over the region. Overnight low temperatures will be 
in the mid to upper 30s for most inland locations, under mostly 
clear skies and with light winds. On Thursday, the high pressure 
center will shift east toward the lower Mississippi Valley, allowing 
a weak return flow to set up. High temps will be in the 60s to near 
70. Thursday night and Friday may be a skosh warmer, but the air 
mass won't have modified too much. East southeast winds will 
strengthen by Saturday, resulting in convergence along the coast and 
a chance of rain for the day. Temperatures will again inch a little 
higher, with 40s and 50s Friday night and 60s to near 70 on 
Saturday. A shortwave trough to the west will edge closer, and may 
contribute to overall instability as it coincides with a surface 
front where enhanced northeast winds will develop, also partly in 
response to a coastal trough of low pressure. The trough will swing 
overhead Saturday night into Sunday, helping to nudge the coastal 
trough farther away from the area, along with the rain and winds. 
Skies should clear through the day Sunday, with high temperatures in 
the mid 60s. Conditions should improve further on Monday as the 
overhead trough moves east and a dry northwest flow develops aloft. 
South winds will pick up on Monday ahead of the next front due 
Tuesday morning. The European, GFS, and Canadian showed non-trivial 
inter-model temperature anomalies at times, but a blend smoothed out 
the extremes. That indicates less certainty, but in this instance 
worst case situations would not appear to significantly impact 
ongoing hazards.


Now through Wednesday: Pressure gradient continues to strengthen
today as low pressure deepens across the Plains and West Texas.
Small Craft Advisory conditions persist across all coastal waters
into this evening with strong southerly winds picking up this
morning. A strong cold front on Wednesday morning shifts winds out
of the north and increases them to gale force. A Gale Watch is in
effect across all coastal waters Wednesday morning, and across
offshore Gulf of Mexico waters into Wednesday afternoon.

Wednesday night through Saturday night: Fresh north winds and high 
seas will linger Wednesday night in the wake of a cold front and as 
high pressure settles over the lower Texas coast. Winds and seas 
will decrease to below small craft advisory conditions by Thursday, 
and will then remain more modest through Friday night. Onshore winds 
will strengthen on Saturday as high pressure centered over the lower 
Mississippi Valley presses south over the Gulf and tightens the 
gradient. Winds will also back to east and then northeast by 
Saturday night.


.FIRE WEATHER...20 foot winds increase from the southeast around 
15 knots this afternoon as temperatures in the 70s and dewpoints 
in the upper 40s to low 50s provide relative humidity values 
generally near 40 to 45 percent across inland counties. These 
conditions are below Red Flag Warning criterion, and no fire 
weather watch is needed. A fire danger statement may be needed for
portions of Deep South Texas if winds are higher and relative 
humidity values are lower than currently forecast. Similar 
concerns exist on Tuesday, with relative humidity values near 40 
to 45 percent and 20 foot winds increasing to 15 to 20 knots 
Tuesday afternoon. 

BAYVIEW/PORT ISABEL  78  49  58  41 /  10  40  30  10 
BROWNSVILLE          78  50  60  40 /  10  40  30  10 
HARLINGEN            82  48  58  38 /  10  40  20  10 
MCALLEN              83  52  61  39 /  10  30  10   0 
RIO GRANDE CITY      84  54  61  37 /  10  20  10   0 
SOUTH PADRE ISLAND   74  52  58  48 /  10  40  30  10 


TX...Wind Advisory from 9 AM this morning to 4 PM CST this afternoon 
     for TXZ254>257-351.

GM...Gale Watch from late tonight through Wednesday morning for 

     Small Craft Advisory for winds until 6 PM CST this evening for 

     Gale Watch from late tonight through Wednesday afternoon for 

     Small Craft Advisory until 4 AM CST Wednesday for GMZ150-155-170-



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