#179 Postby weatherdude1108 » Wed Sep 21, 2016 6:36 am
EWX is on board with a pattern change.
000
FXUS64 KEWX 210855
AFDEWX
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
355 AM CDT WED SEP 21 2016
.SHORT TERM (Today through Thursday)...
Continental sfc to 700 mb easterlies will help to ease up on the
high heat index values seen over the past few days. Broad high
pressure aloft will ensure that the winds remains fairly light,
which means the relief from the heat will be modest as morning
dew points still jump up into the low to mid 70s the next couple
days. A few heat index values should still manage to reach triple
digits over the Coastal Prairies. A weak upper level easterly
trough moves into Nrn Mexico tonight and brings in its wake a
subtle increase in mid-level onshore flow for Thursday. Most of
the models generate some light coastal QPF values that could
spread into our SErn counties by Thursday afternoon.
&&
.LONG TERM (Thursday Night through Tuesday)...
High pressure aloft begins to nudge eastward Thursday night and
further deepen and strengthen the onshore flow pattern in the low
to mid levels. Some seabreeze activity could make some good
progress into inland counties by Friday as a significant pattern
change begins to set up from an approaching high amplitude upper
trough from the Pacific.
Model runs have mostly shown poor consistency on the weekend
projections of the upper low that becomes quite deep as it moves
into the Great Basin on Friday. Ensemble runs show a converging
trend on much of the energy from the trough to drift north while a
secondary upper low deepens just to the west of TX Sunday.
Deterministic runs show this pattern to keep active upper level
wind currents to keep the lows from being completely cut off from
the polar westerlies, so have bought into the more persistent
solutions of the CMC/ECM runs over the past day or so. A consensus
of these runs will tap into a buoyant and unstable airmass from
the Eastern Pacific and set up a good chance for a large complex
of storms along a cold front which moves slowly through the area
Sunday into early Monday. With many of the GFS solutions holding
to a more cut-off upper pattern over Mexico and less strong
convection along the front, will hold off using the mention of
locally heavy rain and the use of categorical PoPs for now. Even
the more erratic GFS runs still maintain a cold front arrival, so
the best news is that the persistent heat will take a break over
the weekend.
Following the trend and favoring of the ECM solutions, increasing
stability is shown for late Monday into Tuesday. Based on the
upper trough position, some variations in sky cover could alter
this forecast, as could the influence of tropical cyclone
acitivity in the Eastern Pacific. For now, crisp morning lows in
the upper 50s to mid 60s are expected for most areas Tuesday and
Wednesday mornings, with highs unable to exceed the middle 80s
each afternoon.
&&
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