Wednesday, December 20, 2017

Dec. 19 17

Northwest Houston, TX, during the early morning.

Northwest Houston, TX, during the early afternoon.
Northwest Houston, TX, during the late afternoon.

Houston, TX radar, during the early night.

Houston, TX radar, during the late night.


Locations: Northwest and west Houston, TX.


Thoughts: I enjoyed the line of thunderstorms that passed through.


Area Forecast Discussion 
Issued by NWS Houston/Galveston, TX

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259
FXUS64 KHGX 200232
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
832 PM CST Tue Dec 19 2017

.NEAR TERM [Through Tonight]...

Radar shows line of storms from Madisonville to Columbus moving
east this evening. Based on current trends and latest short term
model guidance, storms should reach Houston area around 11PM and
then along the coast around 3AM Wednesday. Main changes to the
forecast were to update T/Td trends with ongoing conditions and to
better time the line of storms moving through the area. Overall
environment supports thunderstorm activity but the combinations of
instability, lift and shear are not supportive of severe weather.
Storms may get strong enough for some 30 knot winds as they push
through with frequent lightning. There may be some brief heavy
rainfall but rainfall amounts are expected to remain under a half
inch. Sea fog has developed in the bays and coastal waters but
should erode during the morning as the front pushes off the coast
behind the line of storms. West winds tomorrow should allow for
drier conditions and for high temperatures to reach the upper 70s.
Some areas could reach the low 80s like a few spots did today.

Overpeck

&&


.PREV DISCUSSION /Issued 542 PM CST Tue Dec 19 2017/...

Breaks in the clouds have provided enough insolation for isolated
to scattered showers and even a few thunderstorms to develop this
afternoon. So far activity has been well-behaved, but with the
region located south of a warm front (roughly stretching from New
Braunfels to Jarrell to Palestine) and SPC mesoanalysis showing
25-30 knots of 0-1 km bulk shear would not be surprised to hear of
some transient rotation or funnel clouds from any discrete cells
that develop in the vicinity or south of the warm front through
sunset. A secondary line of showers and thunderstorms is expected
to develop west of the region late this afternoon along the
western extent of the warm front (New Braunfels to Jarrell) as it
pushes back east as a "cold" front. Already starting to see some
development along this feature and expect this line to sweep
across the region during the evening and early morning hours,
clearing sometime closer to 3-4 AM. Increasing forcing for ascent
as a compact upper low reaches North Texas combined with 0-6 km
bulk shear approaching 50 knots may allow for a few of the
thunderstorms that develop to become strong north of a Columbus to
Cleveland line. The main threat is expected to be gusty winds as
a some of the energy from a developing 40 knot low level jet is
transported to the surface by stronger downdrafts, but brief heavy
rain will also be possible with precipitable water values between
1.6-1.8 inches. No flooding issues are expected but localized
visibility restrictions will be possible from the heavy rain.

After the front clears the region, drier air will not only scour
out the sea fog along the coast but allow for the region to warm
into the mid to upper 70s on Wednesday under sunny skies. Return
flow quickly becomes established by Thursday as a lee surface low
develops over the Central Plains, ushering the clouds back in and
chances for warm air advection showers with highs again in the 70s.
Returning moisture will also mean the sea fog threat returns and
persists into Friday ahead of a cold front crossing the region.
Scattered showers and thunderstorms will be possible with the
front with rain clearing the region by Saturday morning as the
front pushes into the Gulf. Highs on Saturday look to be about 20
degrees cooler than Friday with a reinforcing cold front on Sunday
further dropping highs into the 40s.

Medium range guidance continues to trend drier with the late
weekend cold front and expect the beginning of Christmas week to
be cold and dry. Will have to keep an eye on the potential for
widespread freezing conditions Monday/Tuesday morning as a
1028-1030 mb surface high slides across the region.

Huffman

.AVIATION.../00Z TAF/
For the most part, the previous cycle of TAFs is on track.
Developing line of thunderstorms northwest of CLL is a bit slow,
and though it didn`t force a change there, that slight delay will
grow such that most sites downstream needed the arrival of these
storms to be nudged back 1-3 hours. Still anticipating this line
of convection to be thin and broken, so it should move through
relatively quickly and is not guaranteed to impact the sites.
However, if they do, stronger cells are certainly capable of
producing wind gusts in excess of 30 knots.

Meanwhile, at the coast, GLS is back into the marine fog, and is
fairly dense. Webcams in the area are pretty socked in with obs
down to 1/2 mile. This will persist until the front comes to clear
everything out. Did not include LBX at this time, but if fog makes
a greater intrusion inland, that may be cause for an amendment
later tonight.

Luchs


&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL)  54  73  51  76  61 /  80   0   0  10  30
Houston (IAH)          60  78  52  76  65 /  50   0   0  20  30
Galveston (GLS)        62  74  59  73  64 /  40  10   0  20  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...Dense Fog Advisory until 6 AM CST 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...Galveston Bay...Matagorda Bay.


&&

$$

UPDATE...Overpeck
NEAR TERM...Overpeck
SHORT TERM...25

Hazardous Weather Outlook

Hazardous Weather Outlook
National Weather Service Houston/Galveston TX
317 PM CST Tue Dec 19 2017

TXZ213-214-235>238-202130-
Brazoria-Chambers-Galveston-Harris-Jackson-Matagorda-
317 PM CST Tue Dec 19 2017

This hazardous weather outlook is for portions of Southeast Texas..

.DAY ONE...This Afternoon and Tonight

Areas of sea fog will impact the coastal areas this afternoon and
tonight, reducing visibilities to 1 statute mile or less at
times.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Fog may return to coastal areas Thursday and Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated at this time.

$$

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