Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 210901
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
401 AM CDT Tue Mar 21 2017

.DISCUSSION...
Stratus continues to blossom north of Interstate 10 early this
morning. Outside of this stratus deck, radiational cooling has
allowed for patchy fog development. Low-lying or sheltered areas
will be prone to dense fog development, but similar to yesterday
morning anticipate enough mechanical mixing from a 25 to nearly 40
knot low level jet evident on both KHGX and KGRK`s VAD wind
profilers to limit a more widespread threat. Fog will lift shortly
after sunrise as daytime heating/mixing begins.

With upper ridging remaining in place today and amplifying
Wednesday, the short term portion of the forecast will be defined
by near record to record warmth during the day, mild temperatures
and low clouds/patchy fog overnight, and dry conditions. Early
morning surface analysis shows a nearly stationary frontal
boundary located near the Red River, with surface high pressure
located over the central Gulf of Mexico. Given unfavorable upper
support, anticipate little movement of the frontal boundary well
north of the region but the surface high will encourage southwest
to south surface winds to continue across the region today. These
surface winds, in addition to the upper level ridging, will not
only keep the atmosphere very dry (precipitable water values
around 0.5-0.75 inches) but will also help high temperatures again
rise into the mid 80s inland and upper 70s to low 80s along the
coast today and tomorrow. Similar to yesterday, records in a few
locations (Houston Hobby and possibly Galveston today, Galveston
tomorrow) may be in jeopardy. For more information on today`s and
tomorrow`s high temperature records, please see the climate
section below.

Water vapor imagery shows an upper level disturbance churning off
the California coast this morning. As this feature reaches the
southern Rocky Mountains Thursday, associated surface cyclogenesis
over the High Plains will result in increasing onshore flow
Thursday and Friday as the pressure gradient across the region
tightens. This will not only mean breezy to possibly windy
conditions becoming established by Friday ahead of this system,
but will allow for moisture to dramatically increase with
precipitable water values climbing back near 1.2-1.5 inches. The
surface cyclone looks to eject across the Southern Plains on
Friday as its parent upper level disturbance lifts towards the
Great Lakes, dragging an associated cold front into Texas.

A thunderstorm complex is expected to develop along this frontal
boundary as it moves into Texas and CIPS analog guidance provides
that the overall pattern may be favorable for at least some severe
weather threat across parts of Southeast Texas Friday afternoon
and evening. Thunderstorm development along and ahead of the front
on Friday will be aided by 6-10 decameter height falls an 80 to
90 knot jet streak nosing into the region ahead of the trough,
with 0-6 km bulk shear values in excess of 40 knots promoting
storm organization (generally north of the Interstate 10
corridor). However, instability appears questionable at this point
with CAPE forecast to remain under 1000 J/kg during the day
Friday (likely as a result of increasing cloud cover) and have
concerns that model guidance may be underdoing the strength of a
capping inversion given strong mid-level flow out of the south-
southwest to southwest ahead of the upper trough and surface
front. Will need to continue to monitor Friday for the possibility
of a few strong to severe thunderstorms, but confidence is low at
this time.

As the main upper level system lifts away from the region Friday
night, the cold front is expected to stall somewhere across
Southeast Texas on Saturday. Medium range deterministic guidance
is fairly consistent with this being somewhere near or north of
the Interstate 10 corridor and this stalled frontal boundary may
serve as a focus for additional shower or thunderstorm development
during the day on Saturday. However, outflow associated with
Friday`s thunderstorms may allow the boundary to push farther
south and east than currently anticipated... meaning Friday`s
convective evolution will play a big role in what kind of weather
is realized on Saturday.

Shortwave ridging on Sunday should be enough to suppress any rain
chances for the end of the weekend, but a series of disturbances
lifting into the Central/Southern Plains at the beginning of next
week will mean at least low rain chances return in the forecast
Monday. The next major frontal system to impact the region looks
to be beyond this forecast period towards the middle of next week.

Huffman

&&

.CLIMATE...
Daily high record temperatures may be approached or broken at a
few Southeast Texas climate locations today and tomorrow. The high
temperature records for today and tomorrow are listed below.

March 21 High Temperature Records
LOCATION                   RECORD HIGH     YEAR
Houston Intercontinental       87          1907
Houston Hobby                  84          1982
College Station                92          1916
Galveston                      82          1955

March 22 High Temperature Records
LOCATION                   RECORD HIGH     YEAR
Houston Intercontinental       89          1916
Houston Hobby                  90          1971
College Station                94          1971
Galveston                      80          2005

&&

.MARINE...
A light to occasionally moderate onshore flow will continue for
the bays and coastal waters through Wednesday, occasionally
strengthening to near caution criteria each night across the
offshore waters. A strengthening onshore flow ahead of an
approaching storm system may result in caution flags on Thursday
and a Small Craft Advisory on Friday. Seas may build as high as
8-10 feet offshore by Friday morning. Model guidance continues to
stall the next front well inland and an onshore flow is expected
to persist through early next week. The gradient will briefly
weaken on Saturday so lighter winds expected at that time but the
gradient tightens up again Sunday and Monday and Caution flags
will likely be required yet again. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      85  63  86  64  83 /   0   0  10  10  10
Houston (IAH)              85  64  84  64  82 /   0   0  10  10  10
Galveston (GLS)            80  68  79  68  77 /   0   0  10  10  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

Discussion...14
Aviation/Marine...43



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