Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 140534

Area Forecast Discussion
National Weather Service Brownsville TX
1134 PM CST Wed Dec 13 2017

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


.AVIATION...Thick cirrus with light and variable winds prevail
across deep south Texas late this evening. VFR conditions expected
for the next 24 hours (except for perhaps at the very end of the
period if CIG`s lower in rain) while high level clouds gradually
lower to around 10kft overnight into Thursday morning. Rain
chances will begin to increase by late Thursday afternoon as low
level moisture surges in the area. A cold front is expected to
move though the Rio Grande Valley late in the period.


.PREV DISCUSSION... /issued 520 PM CST Wed Dec 13 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Thick cirrus and light winds prevail across deep
south Texas this evening. VFR conditions expected for the next 24
hours while high level clouds gradually lowers to around 10kft
late tonight into Thursday.

PREV DISCUSSION... /issued Issued by National Weather Service NEW ORLEANS LA/

SHORT TERM (Tonight through Thursday Night):
Large expansive cirrus deck invading from the wests through the
Lower Rio Grande Valley this afternoon with a tap well into the
tropical Pacific. This will deepen moisture throughout the column
over time that should become activated with frontal approach from
the Plains later in the day Thursday. Expecting decent coverage of
showers ahead of the front with some over-running precipitation to
continue through Thursday night. This will maintain very small
diurnal temperatures ranges through Friday. Generally about one-
quarter of an inch to three-quarters of an inch on average
anticipated to accumulate across the region through Thursday
night, the greater amounts likely to be in the northern half of
the forecast area.

LONG TERM (Friday through Wednesday):
Cold high pressure wedges southward through Texas to maintain cold
over-running pattern through much of Friday before shutting off
Friday night. Meanwhile, mechanical low pressure area develops off
the coast and gets drawn northward to the central Texas coast
Saturday night. This will tighten the wind gradient considerably
and aid in augmenting the cold air advection into the lower
valley. A re-enforcing cold front forges southward late Monday.

Weak high pressure along the lower TX coast this afternoon will
maintain relatively light winds and low seas through tonight. Some
gradient compression takes place Thursday for moderate onshore
flow ahead of advancing high pressure surge from the north. Cold
front wedges off the coast Thursday night with north winds
increasing to stronger levels during the day Friday through
Saturday. Mechanical low formation off the Mexico coast tightens
the gradient wind heading into Saturday night as the low moves
north and becomes a more mature baroclinic system upon reaching
the upper Texas coast Saturday night. This will maintain strong
northerly winds closer to the coast, but warm sector southerly
flow skirting the outer coastal waters. Cold air advection then
proceeds to push off the coast later Sunday as low pressure system
lifts well northeast of the Texas coast.




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