Scientific Forecaster Discussion
fxus64 kcrp 210005 aaa
Area forecast discussion...updated
National Weather Service Corpus Christi Texas
605 PM CST Wed Nov 20 2019
Updated for the 00z aviation discussion.
A developing southerly low level 35-45 knots jet is expected this
evening and overnight. With surface winds expected to fall below
10 kts from ali-crp-vct, maintained low level wind shear in tafs. Lrd-cot winds
should remain elevated to limit low level wind shear. The onshore flow will
lead to MVFR stratus to develop through tonight, lifting back to
VFR around 15z and beyond. Winds are expected to mix down to the
surface around 15z as well, with gusts of 20-25 kts possible
through the end of the taf period.
Previous discussion... /issued 334 PM CST Wed Nov 20 2019/
Short term (tonight through Thursday night)...
Deterministic runs predict the upper low to move across The Four
Corners region/southwestern Continental U.S. Tonight/Thursday, then lift over the
southern rockies and toward the Southern Plains Thursday night, with
associated 700-300mb q-vector convergence remaining north of the
County Warning Area. However, the deterministic runs predict an upper jet streak
to move north of the County Warning Area tonight/Thursday, then southward and over the
County Warning Area Thursday night. Precipitable water values are expected to remain above
normal and gradually increase during the period. Expect the
combination of upper forcing and greater moisture to generate at
least isolated showers Thursday night (although very limited cape
and significant cin will likely be the limiting factors for
surface-based convection per the NAM deterministic, the upper jet
may lift the convectively unstable layer, located above the
inversion, to increase static instability and contribute to
Long term (friday through wednesday)...
As an upper level low over the Desert Southwest will move east over
the Great Plains Friday and Saturday, upper level ridging over south
Texas will flatten and become zonal. With the low staying well to
our north, there will not be enough forcing for widespread rain
ahead of the front on Friday. Pops will generally be limited to the
coastal Bend and Victoria Crossroads where the better moisture will
be. The timing of the front is still on track, between 18z to 00z.
Wind speeds do not look quite as strong as previous model runs, and
should stay just below Small Craft Advisory criteria through
Saturday. Highs will be about 10 degrees cooler on Saturday, in the
low 70s. By Sunday afternoon winds will shift back to the southeast,
with highs in the low to mid 70s. Overall, a pleasant weekend with
mostly sunny skies.
There has not been much consistency run to run with the trough for
early next week. The GFS keeps it as an upper level low but takes it
across the Central Plains, while the European model (ecmwf) only has a very broad
trough. Both do show a cold front moving through late Tuesday night,
dropping temperatures to the upper 60s to low 70s for Wednesday.
With a lot of uncertainty this far out, have kept pops to 20-30% for
Monday night through Tuesday night.
Expect Small Craft Advisory conditions over the coastal waters
overnight/early Thursday owing to vertical mixing of strong
onshore momentum aloft per the NAM (although mixing will be less
over the nearshore waters given cooler SST values per the sport
SST composite, feel that frequent surface wind gusts to at least
20 knots will occur nevertheless.) Isolated showers may occur
tonight/Thursday. A slightly greater chance for convection
Thursday night owing to the foregoing upper jet streak. Scattered
showers and thunderstorms are expected on Friday ahead of a cold
front. A moderate onshore flow Friday will become offshore by
Friday evening following the front. Rain chances will diminish on
Saturday with drier air filtering in from the north. A light to
moderate northerly flow will persist through the weekend. Weak to
moderate onshore flow will resume Sunday night and become strong
by Monday night.
Preliminary point temps/pops...
Corpus Christi 68 80 68 80 54 / 10 10 20 10 20
Victoria 66 80 66 79 49 / 10 20 20 50 20
Laredo 68 83 67 81 56 / 10 10 20 0 0
Alice 68 84 68 84 54 / 10 10 20 10 10
Rockport 68 78 69 78 54 / 10 10 20 30 30
Cotulla 67 81 66 79 52 / 10 10 20 10 0
Kingsville 68 84 68 83 56 / 10 10 20 10 10
Navy corpus 69 77 69 76 57 / 10 10 20 20 20
GM...Small Craft Advisory until noon CST Thursday for the following
zones: coastal waters from Baffin Bay to Port Aransas out
20 nm...coastal waters from Port Aransas to Matagorda Ship
Channel out 20 nm...waters from Baffin Bay to Port Aransas
from 20 to 60 nm...waters from Port Aransas to Matagorda
Ship Channel from 20 to 60 nm.
Small Craft Advisory until 9 PM CST this evening for the
following zones: bays and waterways from Baffin Bay to Port