Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 231808 AAD

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1208 PM CST Fri Feb 23 2018

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

.AVIATION...Satellite images and surface observations indicate low
to mid level clouds with fog across western portions of the CWA
early this afternoon. Ceilings were near 200ft at KEBG and KHBV to
near 3600ft at KHRL. Visibilities were near 1SM with fog at KHBV
to near 5SM with fog at KEBG. Expect IFR to IFR conditions across
the northern and western portions of the CWA to continue another
hour or two before a warm front across the lower Rio Grande valley
moves northward. VFR conditions will prevail south of the warm
front this afternoon. Low clouds and fog will return late tonight
as mixing decreases with the loss of diurnal heating. Expect MVFR
to IFR conditions to develop late tonight into early Sat morning.

.PREV DISCUSSION... /issued 655 AM CST Fri Feb 23 2018/
DISCUSSION...Updated for latest marine discussion below.

MARINE...Dense fog has formed over portions of the Laguna Madre
and near shore waters and a dense fog advisory has been issued
through 11 am.

PREV DISCUSSION... /issued 549 AM CST Fri Feb 23 2018/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Poor flying conditions prevail this morning as a warm
front moves on shore. LIFR cigs and IFR vsbys are expected through
mid morning then a steadily improvement late this morning and into
the afternoon as the front moves north of the region and
southeasterly winds increase. MVFR mixing with occasional VFR
conditions this afternoon lower back to MVFR Friday evening.
Pressure gradient strengthens today and tonight with moderate
southeast winds developing. Winds are not expected to relax
overnight with gust remaining around 20 knots tonight.

PREV DISCUSSION... /issued 331 AM CST Fri Feb 23 2018/

SHORT TERM (Today through Saturday): Warm front still lurking
offshore is slowly moving westward. Hi-res Rapid Refresh and NAM
suggest the front to move inland mid-morning and accelerate N-NW
this afternoon. Lingering showers and light fog this morning to
dissipate and lift northeast as the front progresses through Deep
South Texas. In it wake, southerly flow strengthens as pressures
lower over the Southern Plains. Breezy conditions expected with
the the lower Valley seeing the strongest wind with gusts near 30
mph later this afternoon. Temperatures warm up significantly with
the southerly flow and with mid level RH`s lower this drier air
should help mix out the surface moisture for some sun to warm much
of the Lower and Mid Valley back into the lower 80s.

Tonight Low level jet strengthens as upper trough moves into the 4
corners area and surface low deepens over the southern plains. Low
clouds and a constant breeze to keep temperature well above normal.
Not expecting fog tonight due to the higher winds lingering. Higher
dew point air along the cooler shelf waters and the Laguna Madre may
allow for the sea fog to reform.

Saturday Low level jet remains strong over the eastern half of the
CWA in the morning with model averages near 40 knots in the 850-
925mph layer. Model guidance continues to show winds approaching
wind advisory criteria through the first half of the afternoon
before the jet lifts to the northeast and offshore. Confidence in a
slam dunk advisory is lower with the last few model guidance runs
trending slightly lower with overall wind speeds but none the less
windy conditions are expected in the Lower Vally with breezy
conditons in the Mid Valley.  Low pressure trough moves into the
western counties with a weak downslope component developing in the
afternoon. The downsloping and sufficient mixing in the east should
push temperatures up into the upper 80s to lower 90s Saturday

LONG TERM (Saturday Night through Thursday): The long term period
will begin with a frontal boundary located over the CWFA. This
should provide support for some showers/storms. Similar to the
frontal passage this week, this front looks to be parallel to the
mid level southwesterly flow, however, if convection does fire,
mesoscale features (i.e. cold pool) would likely be the driving
force behind a complete passage. Regardless, held temperatures
down with rainfall and overcast skies anticipated.

Monday looks continued cool and damp as the front, just south of
the mouth of the Rio Grande River (assuming it is able to slide
completely through) will generate enough isentropic lift to keep
a solid deck of low stratus over the RGV, though there may be a
few breaks across the northern Ranchlands. The frontal boundary
will lift northward fairly quickly Monday night allowing for the
surface flow to shift southerly once again. This will help 1)
allow breaks in the clouds and 2) help temperatures boast back
into the lower and middle 80s as WAA begins. Wednesday looks like
another very breezy day across the RGV. Additionally, it looks
fairly warm too, especially for this time of year with upper 80s
to near 90 degrees expected inland close to the river.

Our next front will be due into the region on Thursday. Globals
are in agreement that the front will again push through the region
once again allowing temperatures to cool going into late next
week. Overall, the synoptic flow doesn`t really change much with
active southwesterly flow aloft being the dominant feature.

MARINE (Today through Saturday): Web cameras not showing to much
dense fog this morning but patches are still expected with the warm
front offshore. Some mixing of the boundary layer should result in
thiner areas of fog through the day with the potential of thicker fog
reforming tonight and Saturday morning. Pressure gradient
strengthens the next 24-36 hours with southerly flow increasing with
a moderate wind and seas regime today. Stronger winds develop
Saturday with Small craft advisory conditions anticipated over the
Laguna Madre and marginal SCA wind and seas over the Gulf waters.

(Saturday night through Thursday): Marine conditions will begin to
improve from earlier adverse conditions on Saturday. A cold front
will begin to stall across the Saturday night which should allow
winds to subside a bit. Sunday through Monday looks somewhat quiet
with winds residing somewhere between 10-15kts. Wave heights will
remain somewhat elevated with moderate northerly flow, however,
should remain below SCA criteria. On Wednesday another cold front
rolls toward the region. This time SCA thresholds look to be met
with winds approaching 20 kts (especially over the Laguna) and
wave heights approach 7 ft plus. Winds should begin to lighten by
Thursday as high pressure moves southward into eastern TX.



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