Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 031218
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
718 AM CDT Fri Apr 3 2020


.AVIATION [12Z TAF Issuance]...

Not a lot of issues so far this morning as the slightly elevated
winds just above ths surface are helping to keep CIGS from lower-
ing too much. However, we are still could see brief MVFR CIGS by
mid morning before lifting by this afternoon. The major forecast
concerns will be during the afternoon through evening hours with
the passage of the cold front and the associated TSRA developing
with this boundary. Near-term model consensus regarding the fast-
er FROPA timing has the front @ CLL late this afternoon (21-23Z)
@ IAH early this evening (00-03Z) and @ GLS tonight (03-06Z). At
this time, did go with the mention of TSRA for most of our sites
but the best dynamics should be over our N/NW counties (CLL/UTS/
CXO). Post-frontal rains will help keep CIGS low overnight. 41

&&

.PREV DISCUSSION... /ISSUED 441 AM CDT Fri Apr 3 2020/

SHORT TERM [Through Saturday Night]...
Frontal boundary is passing across the Red River as of this
writing. Satellite imagery shows a shortwave embedded in the upper
flow over nctl Mexico just ahead of the incoming lfq of the upper
jet. Overall, not much change in the ongoing guidance suggesting
increasing convection this early afternoon just to the north and
west as these features come together...eventually moving across
southeast Texas during the afternoon and evening hours.

There should be a decent amount of instability, mainly west of
I-45 whereas some embedded severe cells can`t be ruled out. Hail
looks to be the primary threat. However what is somewhat unclear
is any evolving storm organization (mergers, maybe brief linear
coalescence, etc) in which case localized strong gusty winds will
also be a possibility. Severe potential should gradually diminish
after sunset.

In regards to the heavy rain potential: PW`s will be on the high
side. Locations roughly north and west of a Crockett-Wharton line
can expect 1-2" of rain on average...less further south and east.
For the past several days, models have shown some signals for the
possibility of localized heavy rain. (Meaning 2-6" bullseyes for
some locations around the area...but inconsistent in regards
placement/locations from run-to-run). This will still need to be
watched...and placement (*IF ANY*) will likely be dependent on
micro/mesoscale storm interactions that haven`t been established
yet. If forced to pick a more favorable isolated location, I`d say
the area along and north of I-10 and west of I-45. The region can
take several inches of rain without a problem - just not if it
all falls in a very short time period.

Though rainfall should continue well into the evening, the overall
intensity should be on a gradual downward trend a few hours after
sunset. Considering the shallow nature of the front and expected
cold pool from precip, we trended the fcst toward a faster fropa
and bring the boundary to the coast or just offshore later tonight.

A messy southwest flow aloft will continue Saturday. Upglide over
the front and continued impulses passing thru in the upper flow
should lead to additional rounds of precip. Assuming the front
remains near/off the coast that`s where the higher totals should
be. Maybe another 0.5-1.5" along and south of I-10. Should be a
steadier type rain & less convective inland which shouldn`t pose
much of a problem. Of note...tides are running above normal which
may lead to slower drainage on the Island.

LONG TERM [Sunday Through Friday]...
The front gradually begins to washout offshore later Sunday and
onshore winds become reestablished Sunday night and Monday. As the
mid/upper trof digs southward along the west coast, slight ridging
should begin to nose into the area from the Gulf. The flow aloft
becomes more southwest and the more favorable trajectories for the
upper disturbances should lift further inland. Scattered
shra/tstms can`t be ruled out any day of the week dependent on
timing of said impulses. But overall, would anticipate diurnally
driven precip along/nw of the Highway 59 corridor into midweek.
Once the western trof decides to kick out into the Plains, we
could see a gradual increase in coverage/chances headed into late
next week.  47

MARINE...
Light/moderate onshore winds to prevail today with only isolated act-
ivity possible through this afternoon. Rain chances should be on the
increase this evening/tonight for the bays/nearshore waters with the
arrival of the next cold front. This boundary is expected to push in
to the Gulf waters overnight...with N/NE winds strengthening through
the day on Sat. Winds/seas could reach SCEC conditions (maybe border-
line SCA) over the coastal waters by Sat afternoon/night. As surface
high pressure over the Northern Plains moves off to the NE, we`ll be
seeing winds decrease/become more E across our marine waters for Sun
and Sun night. Light/moderate onshore winds to return Mon and likely
remain in place for much of next week. 41

HYDROLOGY...
The heaviest rainfall is expected to occur over the Brazos River
Valley, including the Navasota River, which makes this area our
primary concern for new river impacts.  KLG

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      77  54  64  57  75 /  90  90  70  50  30
Houston (IAH)              78  61  71  62  78 /  60  80  80  60  30
Galveston (GLS)            77  69  74  69  76 /  30  60  80  70  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 10 AM CDT this morning for the
     following zones: Brazoria Islands...Galveston Island and
     Bolivar Peninsula...Matagorda Islands.

GM...NONE.
&&

$$



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