Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 240956

Area Forecast Discussion
National Weather Service Houston/Galveston TX
356 AM CST Fri Feb 24 2017

Radar and satellite imagery shows some subtle but interesting
features this morning. First radar shows a lot of anomalous
propagation due to the radar bean essentially being bent into the
ground and returning that energy back to the radar. Temperature
inversion had ducted the bean and then refracted the beam back to
the ground. This is most evident over the Gulf where there are
higher reflectivity. These are not storms since there is a ring of
reflectivity equidistant from the radar. Secondly satellite
imagery on the 11-3.9 micron channel shows a gravity wave or
undular bore that has formed along a pre-frontal trough. Gravity
waves are located from near Palestine to Bryan/College Station
and then to Austin. Winds shifted to the NW at College Station
with its passage. This feature will probably be better observed on
visible satellite imagery as the sun rises.

Surface analysis at 09Z shows the actual cold front still back
over north Texas through the Big Country. Cold front will push
through the area today likely reaching College Station around 11AM
to noon, Houston around 4-5pm and then off the coast around 9PM.
It should be another day with high temperatures in the 80s. Right
now think 84F looks good for IAH and HOU. Record high temperature
at IAH is 87F but only 83F for HOU. Record high temperature at GLS
is 76F and that is a good bet to fall with a forecast high of
79F. Boundary layer flow will turn SW to W. Temperatures at 850mb
should reach 20C ahead of the front and there may be some
compressional heating ahead of the front as well. Moisture is
limited today so do not expect any shower activity ahead of the
front. Dewpoints will be falling into the 40s behind the front
this afternoon so relative humidity may drop below 30 percent in
some areas. This will increase the risk for rapid fire growth but
winds will still be around 10 mph from the northwest behind the
front. Similar conditions are expected Saturday but winds will be
decreasing through the day.

Upper air analysis and water vapor imagery show a broad upper low
over much of the northern Rockies and Plains. A strong jet stream
was located over the southern Rockies and looks to move into
Texas today. Another short wave trough was located off the coast
of British Columbia. This wave should rotate through the mean
trough dropping across California and reach the southern Rockies
Sunday. This shortwave trough then shears out some over the
southern Plains on Monday. There should be enough moisture return
Sunday into Monday in response to the wave that there will be at
least some chance of rain. The forecast will keep mainly 20/30
PoPs through Monday. The system should clear the area Monday night
into Tuesday and allow for high temperatures back near 80F for
the last day of February.

The GFS/ECMWF/CMC all show a strong cold front pushing through
the area on Wednesday. There may be enough moisture for at least a
line of showers. ECMWF/CMC are more robust with QPF during this
time while the GFS is much drier. Forecast will go with some 20
PoPs for now as instability will be limited and there should be at
least some capping with 850mb temps back near 20C again. This
front should last longer with lower temperatures back near normal
for the end of next week. There are some differences in model
solutions for the end of next week. GFS has shown a coastal trough
or low developing with quite a bit of QPF along the coast. ECMWF
has no such system and is much weaker with a closed low over Baja
peninsula. The forecast will go with some 20 PoPs for the end of
next week to account for the possibility of the GFS but overall
confidence is pretty low with this part of the forecast.



Southerly winds have been very slow to come down overnight, and
SCECs are now in place for the bays and nearshore waters until
early morning, and into the mid-morning for the offshore zones.
Additionally, stronger winds have necessitated a brief small craft
advisory through mid-morning. Advisory winds are being measured
in the lower 20-60 nm zone, and with winds around 20 knots in the
0-20 nm waters farther up the coast, will go ahead and do both of
the offshore zones in an abundance of caution, though the upper
zone is very marginal.

After coming down a bit, winds should stiffen again in the wake
of a cold front passing through the area tonight, and may even
flirt with advisory levels again. Beyond that, much of the next
several days looks to see winds near or at SCEC levels for at
least the offshore zones. An advisory may be needed in the middle
of next week as gusty northeasterly winds and building seas are
expected in the wake of yet another front.



Cooler, but significantly drier air will follow a cold front
across the area this afternoon. Relative humidity will at least
flirt with RFW thresholds late afternoon, and in localized areas
in the west, should meet them easily. Fortunately, winds should
fall short. A similar story tomorrow with humidity near or just
above warning thresholds, but weaker winds are expected as high
pressure works in. Additionally, while the low humidity may dry
very fine fuels, recent rains should keep heavier fuels in the
wettest 50 percentiles for both fuel moisture and (predictably)
ERC. Bottom line: weather factors may support more vigorous
burning for fires in exclusively grassy fuels for the next couple
of days. But generally wetter fuels and a lack of stronger winds
should mitigate a serious fire weather threat.



College Station (CLL)      79  43  62  44  71 /  10   0   0  10  30
Houston (IAH)              84  48  67  44  73 /  10   0   0  10  20
Galveston (GLS)            79  55  65  57  71 /  10   0   0  10  10


     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...Galveston Bay...
     Matagorda Bay.

     Small Craft Advisory until 9 AM CST this morning for the
     following zones: Waters from Freeport to the Matagorda Ship
     Channel from 20 to 60 NM...Waters from High Island to
     Freeport from 20 to 60 NM.



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