Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Amarillo Texas
548 am CDT Monday Apr 21 2014
low clouds and visibilities are dissipating across the panhandles
this morning. VFR will prevail through the majority of this taf
issuance. A wind shift to the north is expected at the terminals
around 15z with a few gusts up to 30 kts. Winds will continue to
veer before return to a southerly direction by the end of this taf
period. There is a chance for MVFR conditions towards 10-12z tomorrow
but confidence is too low to include in prevailing.
Previous discussion... /issued 453 am CDT Monday Apr 21 2014/
a bit of a cloudy start to today will quickly turn into a pretty
nice day across the Texas and Oklahoma panhandles. An early morning
cold front will drop across the panhandles to shift winds out of the
north however, temperatures will still be able to warm into the upper
70s to near 80. Another warm day with highs in the 80s can be
expected on Tuesday as winds Switch Back to a southerly direction.
Long term...Wednesday through Monday
An active west-southwest upper flow pattern to begin the long term will
eventually transition to a cooler (maybe downright colder?) And
drier northwest flow pattern by next week. The periods of focus will be
with an upper level system/surface dryline on Wednesday and another upper level
low over the weekend.
models continue to be in surprisingly solid agreement on the
evolution of the Wednesday system, especially given the inherit
difficulties with forecasting both the eastward of extent of a surface
dryline and the timing of lead shortwave ripples. Confidence has
increased some on afternoon storm potential in the eastern panhandles
and have upped probability of precipitation to 30 percent from 20. Medium range models have
trended the afternoon dryline location slightly back west over the
past several runs and this seems feasible given the location of the
upper system and associated forcing well north of US. Have spread
slight chance probability of precipitation westward to account...though eastern areas definitely
still remain favored.
Storm chaser/weather nerd version...
this system has a good deal going for it, including strong surface
convergence along an advancing dryline...modest middle and upper level
diffluent flow overspreading the area...a Gomex moisture source that
is open for business...and what is forecast to be a very
"overcomable" weak eml. Negative factors for convection include
questions about timing of shortwave ripples in the upper flow and
potential for low clouds east of the dryline...though these
questions seem to be outweighed by the overall setup.
Think that as the advancing dryline sharpens in the afternoon hours
Wednesday...diffluent flow aloft will be enough to fire isolated to
scattered convection in the early to middle afternoon hours...probably
just off The Caprock near or east of a Guymon to Amarillo line. In
the presence of modest instability (1500-2000 j/kg mlcape)...
aforementioned flow aloft will produce bulk shear values sufficient
to support supercells with large hail and damaging winds the main
threats. With surface dewpoints only likely to reach into the upper 50s and
expected local heights at or above 2000m...the Wednesday tornado threat looks low at
this time. Convection may linger into the evening hours in the far
eastern panhandles before clearing the area by midnight.
Thursday and Friday...
should be pleasant and dry days...though there is some uncertainty
on friday's highs due to a potential cold front indicated by the
Saturday and Sunday...
medium range model solutions diverge greatly in this period and have
concerns that the major deviation of the GFS from its past runs and
current runs of the European model (ecmwf) and Gem is not something to sneeze at. It
seems that when the GFS makes a large shift in the dy5-ish
timeframe...it is something to watch carefully as many times the
European model (ecmwf) and Gem will follow the lead a run or 2 later. For now...have
only hedged the forecast slightly toward the GFS, which would be
good news for the panhandles as it portrays an upper low moving right
overhead with increasing precipitation chances Sat night and sun. Needless to
say...confidence in next weekend's forecast is below normal.
Early next week...
despite the differences in the models over the weekend...there seems
to be notable trend toward colder northwest flow early next week. We'll
have to wait and see...but if trends continue...we may be talking
about yet another very late season freeze by this time next week.
No elevated or critical fire weather conditions are expected through
Tuesday. Critical fire weather conditions are all but certain on
Wednesday across western sections of the panhandles in very dry air
behind a dryline. Considered issuing a Fire Weather Watch for these
areas...but would like to have better confidence in dryline location
before delimiting an area. The western stack of Panhandle counties
will be behind the dryline by early afternoon Wednesday...but further east
Elevated to critical fire weather conditions will be possible again
next weekend across mainly the western half of the panhandles...
though much uncertainty exists in the forecast for next weekend.