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Area forecast discussion
National Weather Service Houston/Galveston Texas
issued by National Weather Service Tallahassee Florida
235 PM CDT Wed Oct 23 2019

Short term...[through thursday]

The region will be under a transition period through the short
term as high pressure anchored over the eastern United States
quickly translates east into the western Atlantic while an upper
level disturbance (currently over western montana) begins to
amplify over the Rocky Mountain front. Dry conditions are
expected tonight but as winds gain an additional southerly
component on Thursday, we'll see shower chances slowly increase
from west to east through the day as moisture content rises. Main
forecast challenges reside in the long term period, specifically
the Thursday night through Friday period as a tropical airmass
combined with a strong mid-level disturbance produce widespread
heavy rainfall.


Long term...[thursday night through wednesday]

Strong southeasterly flow in advance of the mid-level disturbance
will potentially aggravate minor coastal flooding already in
place across the region (see current beach hazards statement) so
will need to monitor in future updates on the possibility of a
coastal flood advisory. Main forecast concerns Thursday night
through Friday afternoon revolve around heavy rain as a tropical-
airmass and coastal-low interact with a mid-level disturbance and
cold front to produce widespread 2 to 5 inch rainfall amounts
across the forecast area. Isolated locations could see higher
amounts. This threat is outlined in the latest 2 day excessive
rainfall outlook from wpc with a slight risk of flash flooding
Thursday night into Friday morning/afternoon as this system moves

The threat for heavy rainfall likely ends by Friday evening
(potentially earlier) as the cold front pushes through the
region. The latest guidance today has come into much better
agreement on this scenario compared to previous runs 24 hours ago
but we want to note that there still are large differences in
rainfall amounts, and ending times of the heavy rain threat.
Cooler conditions move through the day Friday behind the front
with breezy conditions likely, especially over our Gulf waters
where advisory level winds are likely (see marine discussion).
Will need to watch for potential gale-force gusts behind this
front, but for now it appears the strongest gusts will remain
further south down the Gulf Coast. Winds die down through the day
Saturday with advisory level winds over our waters likely to end
by Saturday morning/afternoon.

Quieter conditions move in for the remainder of the forecast
period with drier northerly flow prevailing through the early part
of next week. Model differences begin to emerge by mid-next week
so kept pops near climo through by the middle of next week.


VFR conditions are expected through the early part of the taf
period. Winds are expected to increase and shift to easterly as
an approaching cold front over West Texas progresses toward the
region, which will force the high pressure mentioned in the
previous taf period to lift to the north and increase the pressure
gradient across the region. The disturbance in the Bay of
Campeche will approach from the south and will fuel the moisture
advecting into the region and will likely lead to MVFR ceilings
across the southern and western taf sites towards the end of the
taf period.


high pressure over the eastern US will keep elevated
easterly/southeasterly flow through Thursday evening across area
waters. This will keep cautionary winds and seas in the forecast
for our offshore waters while inland waters will remain choppy.
Attention turns to another cold front Friday with easterly flow
quickly transitioning to northerly flow in the evening and through
the weekend. Widespread showers and some thunderstorms are
expected over are waters Thursday night into Friday. Advisory
level conditions are likely Friday night into Saturday behind the
front with winds and seas slowly diminishing through the late
weekend and into next week.


Preliminary point temps/pops...
College Station (cll) 59 83 54 64 46 / 0 20 80 40 20
Houston (iah) 62 81 60 67 51 / 0 20 80 60 30
Galveston (gls) 72 80 65 71 57 / 0 30 80 70 30


Hgx watches/warnings/advisories...
GM...small craft should exercise caution through Thursday morning for
the following zones: coastal waters from Freeport to
Matagorda Ship Channel Texas out 20 nm...coastal waters from
High Island to Freeport Texas out 20 nm...waters from Freeport
to Matagorda Ship Channel Texas from 20 to 60 nm...waters from
High Island to Freeport Texas from 20 to 60 nm.


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