Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus64 khgx 250859 

Area forecast discussion
National Weather Service Houston/Galveston Texas
359 am CDT Tue Apr 25 2017

early morning surface analysis shows southeast Texas situated in
between ridging over the northern Gulf and an area of low pressure
centered near the Texas/Oklahoma panhandles. While another dry
day is expected for the region, southerly winds will become breezy
today around 10-20 miles per hour in response to the low pressure system.
Not currently planning on issuing a Wind Advisory given the
anticipated strength of the pressure gradient across southeast
Texas during the day, but the khgx VAD wind profiler is showing
southwest winds 30-35 knots around 1000-2000 feet above ground level and could
see a few of these gusts reach the surface later this morning. In
addition to breezy conditions, this onshore flow will also
promote warmer temperatures than yesterday with highs in the low
to mid 80s as well as allow Gulf moisture (and humid conditions)
to return.

As a shortwave trough over Washington on GOES-16 6.95 micrometer
water vapor imagery this morning dives towards the Southern Plains
tonight, the surface low will eject eastward towards
Arkansas/Missouri ahead of it. Breezy conditions are expected to
continue through the night as the surface pressure gradient
remains elevated in response to this system, with a few warm air
advection type showers possible across parts of the Brazos Valley
early Wednesday morning. Otherwise, increased moisture and
elevated winds will result in overnight lows only falling into the
low to mid 70s Wednesday morning... which may endanger a few
record high minimum values.

As the surface low continues eastward on Wednesday ahead of the
associated shortwave trough, it is expected to drag a cold front
across Texas and into southeast Texas Wednesday afternoon and
evening. Increasing southwest flow in the mid levels at the same
time will result in warming mid-level temperatures/ a
strengthening cap Wednesday morning. A few warm air advection
showers will be possible beneath this cap across most of southeast
Texas on Wednesday morning and will need to keep an eye on how
the cap evolves through the day for thunderstorm potential with
the cold front on Wednesday afternoon and evening. Ahead of the
front, afternoon temperatures are expected to range from the mid
80s over the eastern counties to near 90 over the western
counties. Record high maximum temperatures may also be in danger
along the coast on Wednesday afternoon.

Several high resolution models break out a line of thunderstorms
along the cold front as it pushes southeast into eastern Texas and
western Louisiana, but differ on the southward extent of
thunderstorm development owing to the presence of the cap in
place. Anticipate some mid level cooling to occur during the
afternoon hours as the shortwave trough approaches the region,
which would support the potential for some convective development
within the region. Given the trajectory of this trough and
anticipated timing of the frontal boundary during the afternoon
and evening hours, currently expect areas east of a Madisonville/
Huntsville/ Cleveland line to have the best chances for seeing
development. Should thunderstorms develop (and again, that's still
questionable given the cap), 0-6 km bulk shear values in excess
of 50 knots will promote storm organization with a few possibly
becoming strong and capable of gusty winds or hail with mid-level
lapse rates around 7.5 c/km. Expect the front and any associated
thunderstorms to push east of the region late Wednesday evening,
with temperatures inland falling back into the 50s by Thursday

The front will have little overall impact on temperatures through
the end of the work week with highs remaining in the mid 80s to
near 90 Thursday and Friday with generally dry conditions
expected. An upper level disturbance now over the northern Pacific
is expected to reach Texas on Saturday, resulting in surface
cyclogenesis over West Texas. As this system ejects northeast over
the weekend, it will drag another cold front across southeast
Texas late Saturday night into Sunday, with showers and
thunderstorms developing along the front. Another round of breezy
to windy conditions are expected inland on Saturday ahead of the
front's arrival with thunderstorms along the front capable of at
least locally heavy rainfall as precipitable water values approach
1.8 inches. Drier conditions are expected behind the front on



moderate to occasionally strong onshore winds will persist today
through Wednesday morning as deep low pressure moves across North
Texas. Will maintain caution flags for the Gulf waters for today
and issue an Small Craft Advisory for the Gulf waters tonight through 15z
Wednesday. The winds will briefly decrease Wednesday afternoon as
a cold front nears the coast. The front should cross the coastal
waters between 700 and 1000 PM with high pressure quickly building
into the region in the wake of the front. Winds will also briefly
increase Wednesday night and an scec may be required. The surface
high over Texas will move east on Thursday and onshore winds will
return on Thursday. The pressure gradient will tighten
significantly on Friday as low pressure develops over West Texas.
A strong onshore flow is expected Saturday and Saturday night and
an Small Craft Advisory will likely be required. A cold front will cross the
coastal waters Sunday morning with an abrupt wind shift to the
north. High pressure will settle over Texas Sunday night with
light NE winds on Monday becoming east as the sfc high moves east.

With the long southerly fetch in place across the western Gulf
early this week and again late this week, waves across the
offshore waters are expected to build into the 7-11 feet range at
times. This fetch may also result in elevated tides/coastal flood
issues and strong rip currents along Gulf facing beaches by late
this week. Tide levels Fri/Sat could exceed 3 feet early Wed
morning and early Friday morning. 43


Preliminary point temps/pops...
College Station (cll) 85 72 87 52 84 / 0 10 20 10 0
Houston (iah) 84 73 87 56 84 / 10 10 30 20 10
Galveston (gls) 79 76 83 65 78 / 10 10 20 10 10


Hgx watches/warnings/advisories...
GM...Small Craft Advisory from 5 PM this afternoon to 7 am CDT
Wednesday for the following zones: Matagorda Bay.

Small craft should exercise caution from 6 am CDT this morning
through this afternoon for the following zones: Matagorda

Small craft should exercise caution from 6 am CDT this morning
through Wednesday morning for the following zones:
Galveston Bay.

Small Craft Advisory from 5 PM this afternoon to 10 am CDT
Wednesday for the following zones: coastal waters from
Freeport to the Matagorda Ship Channel out 20 nm...coastal
waters from High Island to Freeport out 20 nm...waters from
Freeport to the Matagorda Ship Channel from 20 to 60 nm...
waters from High Island to Freeport from 20 to 60 nm.

Small craft should exercise caution through this afternoon for
the following zones: coastal waters from Freeport to the
Matagorda Ship Channel out 20 nm...coastal waters from High
Island to Freeport out 20 nm...waters from Freeport to the
Matagorda Ship Channel from 20 to 60 nm...waters from High
Island to Freeport from 20 to 60 nm.


National Weather Service Glossary of Abbreviations