Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Fort Worth Texas
557 PM CST Sat Feb 28 2015
Challenges will continue to be timing -fzra/-fzdz to -ra/-dz this
evening across the dfw metropolitan airports...as temperatures vary from
30-32f. In addition...timing ceilings from IFR to LIFR/or possibly
vilfr/ and visibilities down from MVFR to IFR will be tricky.
We currently are still awaiting our 00z forward sounding...but the
12z forward sounding already showed warm air advection around 850mb in full swing
well in advance of strong upper trough digging over Nevada/CA/AZ this
evening. Have decided to extend -fzra/-fzdz wording at metropolitan
airports until 02z with aformentioned temperatures. However...any light
precipitation should not aggregate on aircraft in any extreme
manner with temperatures hovering at the freezing point. We expect
surface temperatures to slowly modify above freezing through midnight
with the strengthen warm air advection and winds above the shallow Arctic frontal
inversion. Winds will remain north/NE less than 10 kts throughout...so
any warm up will be very slow with precipitation falling into the
cold layer and snow pack still on the ground. Will prevail IFR
through late evening...then LIFR/vlifr through midday Sunday...
back to IFR Sun afternoon.
Waco regional will have similar trends just Sans the freezing
precipitation which temperatures above freezing now.
Previous discussion... /issued 345 PM CST Sat Feb 28 2015/
temperatures will remain near steady or slowly warm tonight with
the freezing line at sunset roughly from Goldthwaite to
Weatherford to Gainesville. We expect periods of light freezing
drizzle in locations along and west of the freezing line with
periods of mainly drizzle or very light rain elsewhere. We have
decided to extend the Winter Weather Advisory until midnight for
locations west of a line from Goldthwaite to Weatherford to
Mineral Wells and let the current Winter Weather Advisory expire
at 6 PM for all other counties that currently remain in the
advisory. The snow cover today has been largely responsible for
the slow warmup as evident by the more rapid warmup in the
counties that saw very little measurable winter precipitation.
Additional ice accumulations should be negligible overall but the
addition of even light icing to already icy spots will continue to
create travel impacts. We expect that all sites will warm to
freezing or slightly above overnight as the shallow Arctic airmass
continues to slowly modify due to relatively warm precipitation
falling through it.
Temperatures Sunday morning should be above freezing with the
exception of a few extreme northwest counties. Strong low level
warm air advection will continue over the slowly modifying Arctic
airmass to produce periods of light rain or drizzle along with
overcast skies and some patchy fog. Highs on Sunday will be
generally in the 40s...except for some upper 30s in the north and
50s in the south.
A secondary surge of cool air will move across North Texas Sunday
night as a short wave rotates across the Upper Middle west.
Temperatures Sunday night will cool mainly into the 30s and 40s
but should remain above freezing. Lift supplied by the cold front
in combination with some weak large scale lift from an approaching
Pacific trough will bring a chance of showers to the entire region
Sunday night through Monday. The upper trough in the Pacific will
deepen near Southern California Monday night while a surface
trough deepens across the Central Plains. This pattern will bring
a surge of warm and moist air northward into North Texas Monday
night through Tuesday. Middle level lapse rates will also increase at
the same time due to increasing large scale lift and this will
result in a chance of thunderstorms. The best chance of storms
will be Tuesday afternoon and Tuesday evening when a pre-frontal
trough moves in from the west. Vertical wind shear and
instability may be sufficient to support some strong
thunderstorms...especially east of the Interstate 35 corridor late
Tuesday afternoon and Tuesday evening.
A strong cold front is prognosticated to move across North Texas Tuesday
night and bring much colder air and windy conditions. Since the
upper low will still be west of the region at this time...there
will be a potential for more winter weather Wednesday through
Wednesday night. It is much too early to assess the potential
impacts from this event but forecast soundings suggest that sleet
would be the primary precipitation type and if model quantitative precipitation forecast is
correct...it could be measurable and possibly significant. All
precipitation should end by Thursday as the upper trough axis
passes to the east.
West to southwest flow aloft should set up across North Texas
next weekend with slowly warming temperatures and no precipitation.
Preliminary point temps/pops...
Dallas-ft. Worth, Texas 33 42 40 52 52 / 40 40 50 40 50
Waco, Texas 35 46 43 55 55 / 40 40 50 40 40
Paris, Texas 32 42 38 41 41 / 50 50 60 50 50
Denton, Texas 33 41 39 47 47 / 40 40 50 40 50
McKinney, Texas 33 43 39 47 47 / 40 40 50 40 50
Dallas, Texas 33 48 44 52 52 / 40 40 50 40 50
Terrell, Texas 33 45 40 48 48 / 50 50 60 50 40
Corsicana, Texas 36 47 43 56 56 / 50 50 60 50 40
Temple, Texas 36 53 45 57 57 / 40 40 50 40 30
Mineral Wells, Texas 32 42 34 47 47 / 40 30 40 40 50
Winter Weather Advisory until 6 PM CST this evening for
Winter Weather Advisory until midnight CST tonight for txz091-