Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 210921

Area Forecast Discussion
National Weather Service Houston/Galveston TX
421 AM CDT Wed Oct 21 2020

.SHORT TERM [Today through Thursday]...

Increasing clouds and areas of fog are the main weather features early
this morning. We`ll be monitoring for possible dense fog advisories.
Temperatures should bottom out in the upper 60s to lower 70s inland
and in the mid 70s at the coast. After the fog lifts and dissipates
after sunrise, expect partly cloudy skies across the area with another
day or above normal high temperatures ranging from the low to mid 80s
at the beaches to the mid to upper 80s inland. There could be some
isolated shower development in/around our southwest counties, mainly
to the west of the Brazos River. Late night through early morning
clouds and some more fog chances can be expected again tonight through
tomorrow morning with overnight low temperatures similar to what the
area experiences this morning. Only change on Thursday might be a slight
tick upward for rain chances with the best location still anticipated
to be generally near and to the west of the Brazos River.  42


.LONG TERM [Thursday night through Wednesday]...

The extended period continues to be characterized by two frontal
passages - an initial weaker boundary on Friday which should prove
rather uneventful for SE Texas and a second, stronger boundary early
next week which still has a significant amount of uncertainty
regarding its timing and impacts.

Expect the unseasonably warm and humid conditions of late to
continue through the end of the work week. Latest surface analysis
continues to indicate broad high pressure over the eastern/
northeastern CONUS and lower pressures over central/western TX. This
synoptic pattern should persist through Thursday, with the resultant
onshore wind allowing for afternoon highs to reach the mid to upper
80s and dew points to remain in the upper 60s to lower 70s. While
won`t be out of the question to see a streamer shower or two develop
offshore in the morning hours during this time, limited mid/upper
level forcing support and low-level capping should inhibit any
widespread precipitation development.

The initial cold front will approach the Brazos Valley-Huntsville-
Crockett corridor by late Friday afternoon, advancing into the
Houston metro overnight and moving offshore by the early morning
hours. Global guidance continues to show a shallow boundary with
little to no frontogenesis signal present above the 850mb isobaric
surface. As such, the impacts from this first FROPA should be
largely inconsequential. Northerly winds will briefly develop in the
wake of the departing boundary, which should knock down high
temperatures by a couple of degrees on Saturday afternoon (though
still remaining above normal for mid to late October). This will be
only momentary, however, as high pressure behind the boundary will
quickly shift eastward and allow for a redevelopment of onshore flow
by Sunday afternoon.

With onshore winds persisting through the remainder of the weekend
and into the early portion of next week, unseasonably warm
conditions will stick around through Monday. Significant uncertainty
enters the forecast beyond Day 5 as a potential second stronger cold
front approaches SE Texas, though models are in a bit better
agreement than at the previous package`s issuance. As of the 00Z
model cycle, GFS remains the faster solution compared to the ECMWF,
placing a strong surface front across the northern counties on
Monday afternoon and offshore by Tuesday morning. EC continues to
stall the boundary before it reaches the coast, but still brings a
post-frontal wind shift and intrusion of cooler and drier air to
most of the area by Tuesday night. Significant spread still showing
among forecast overnight lows on Tuesday and Wednesday, with GFS
remaining ~7-10 degrees cooler across the board compared to the EC.
Given the uncertainty still present, have opted to side with
national blends along with surrounding forecast offices. Despite the
uncertainty present, this second FROPA should be our first real shot
at widespread rainfall during this forecast period, with stronger
convergence along the boundary and more ample moisture availability




Light to moderate northeast to east winds and elevated seas will persist
through the end of the week. Caution flags might be needed. North to
northeast winds can be expected Friday night and Saturday after the
passage of a weak cold front. Onshore winds will return to the area
on Saturday night and will persist into the start of next week. 42



12Z TAFs will show improving conditions (lifting ceilings/fog) in
the morning with VFR in the late morning through afternoon hours.
Later this evening and especially overnight through tomorrow morning,
expect to have another round of low cloud and fog development (mainly
MVFR/IFR). Similar to this morning, look for lifting ceilings and
fog dissipation beginning shortly after sunrise. 42


College Station (CLL)      87  67  87  68  86 /   0   0  10   0  10
Houston (IAH)              87  70  86  71  87 /   0   0  10  10  10
Galveston (GLS)            83  75  82  75  85 /  10   0  20  10  20



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