Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 170306

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1006 PM CDT Sat Sep 16 2017

Anticipating another night of patchy fog development with
localized dense fog occurring after 3 or 4 AM across non-metro
open expanses and or in the vicinity of bodies of water. Similar
temperature behavior as over the past few days with low to mid 70
minimum morning temperatures...lower 90 maximum temperatures under
partially cloudy skies and a southeasterly breeze. A few daytime
subtle elements coming into play tomorrow that will increase
southern third CWA/Gulf-local Bay POPS into the 20 to 30% realm.
One is a possible subtle mid-level boundary that may be the reflection
of a lower level sea breeze inland intrusion. Behind this boundary...a
higher slug of Gulf moisture that should increase current near inch
pwats up to around 1.5 inches by the end of the day. Higher mid-level
offshore omega advecting inland within the heat of the day may be
enough to get some scattered showers and a rogue storm to form
near the coast and move further inland during the mid to late
afternoon hours. Higher POPS will be focused across the nearshore
Gulf waters early in the day and then spread into the first two
tier counties by mid afternoon. 31


.PREV DISCUSSION... /ISSUED 629 PM CDT Sat Sep 16 2017/


00Z Aviation...Expect patchy fog again early tomorrow morning.
Also, expect a few showers around the coast in the early am
hours. Isolated to scattered showers are expected along the
seabreeze boundary tomorrow inland. 33


PREV DISCUSSION... /ISSUED 313 PM CDT Sat Sep 16 2017/


SHORT TERM [Tonight Through Monday Night]...
GOES 16 visible satellite imagery shows southeast Texas covered
with cloud streets with little if any vertical development. After
having below normal temperatures the first week or two of
September, it is feeling like summer again with temperatures this
afternoon in the low 90s and dewpoints in the upper 60s to low
70s. Upper level analysis shows weak ridging aloft but it is
certainly enough to keep convection from forming this afternoon.

GOES 16 derived precipitable water imagery shows a plume of
higher moisture over the central Gulf. This will be the main
reason for increasing rain chances Sunday and Monday. NAM/GFS show
precipitable water values greater than 2 inches getting into the
region mainly on Monday. This should support scattered showers and
a few storms mainly on Monday but model QPF fields suggest more
isolated thunderstorm activity. The other question will be the
sinking motion in the atmosphere due to the ridge. The ridge
really does not break down much until late Monday with maybe a
weak subtle vorticity maximum that pushes across Texas Monday
evening. Any rainfall we do get will soak well into the ground
since much of the area has not really had any rainfall since

LONG TERM [Tuesday Through Saturday]...
Upper level flow for next week basically changes from quasi-zonal
on Tuesday to an amplified pattern as another long wave trough
develops over the western U.S. The ridge develops through the end
of the week over much of Texas and the Mississippi River valley
through next Friday and Saturday. Deeper moisture does remain in
place through the week so forecast will keep 20 to 30 percent
chances of rain going. Models are hinting at higher rain chances
on Thursday but this largely depends upon another surge of
moisture from the Gulf. This seems to be overdone by the GFS but
ECMWF/Canadian are at least hinting at better chances as well. The
bad news about this upper level pattern is that it does not
support any cold front pushing into the area. To get that, we
would need to ridge to develop over the western U.S and the trough
to develop over the Plains through the New England states.

Overall there should be very little weather impacts this week,
just your typical summer time isolated to scattered showers and
storms that can drop a brief downpour. 39


College Station (CLL)      70  91  72  92  74 /  10  10  10  30  10
Houston (IAH)              72  93  74  89  75 /  10  30  10  40  10
Galveston (GLS)            78  89  78  87  78 /  10  30  20  30  20




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