Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Fort Worth Texas
655 am CDT Tue Oct 17 2017
No concerns. VFR will prevail with clear skies.
With a surface ridge draped across North Texas, winds are calm
early this morning. The metroplex airports can begin the day in
south flow with southeast winds ensuing on the back side of the
ridge axis. Southerly winds may reach or exceed 10kts on
Wednesday, but decided a separate line is not really needed at
Winds will be slower to veer across central Texas with light
easterly flow dominating today. South winds will return to Waco
this evening as the ridge axis slips southeast.
Short term... /issued 420 am CDT Tue Oct 17 2017/
with clear skies, low humidity, and light wind, radiational
cooling overnight has been very effective. As typically occurs on
nights like this, variations in urbanization, surface type, and
relief have yielded a wide range in early morning temperatures.
This includes the usual ~15f difference in Wise County between
low-lying, Lakeside Bridgeport (864ft) and the Hillcrest at
Decatur (1047ft). Among the recent additions to our hourly Airport
Arsenal are those on the Eastland County slope. Eastland Municipal
(1468ft) is within the River Valley of the Leon river's North Fork
while cisco's Simmons Airport (1711ft) is among the highest spots
in our County Warning Area. Eastland dipped into the 30s shortly after midnight,
but 13 miles to the west at Cisco, it has remained in the 50s.
The sun will quickly erase these differences this morning, and the
entire region will see 70f by early afternoon. The calm winds
within the nocturnal boundary layer are masking the synoptic wind
field across North Texas, but there is evidence of return flow in
our western zones. Moisture will be slow to return, and the
combination of warm advection and a dry boundary layer will result
in a large diurnal temperature range. The warmest high temps will
be across our western zones where the Mercury may flirt with 80f.
A surface ridge, remnants of our recent autumn air, will remain
draped across the region. This will keep easterly flow in place
across our southern and eastern zones this afternoon. However,
speeds will likely be too light to impede temperatures from
exceeding monday's highs.
Although southerly surface flow will dominate tonight into
Wednesday morning, the ridge axis may be slow to depart, resulting
in minimal warm/moist advection. Regardless, wednesday's low
temperatures will be warmer than this morning's values regionwide.
With clear skies prevailing, temperatures will fall into the 40s,
the exception being urbanized portions of the Dallas/Fort Worth
metroplex, which will likely bottom out in the 50s.
Long term... /issued 420 am CDT Tue Oct 17 2017/
/Wednesday through next Monday/
A shortwave ridge aloft will maintain the dry sensible weather
across the area with increasing south winds and low level warm
advection helping to fetch better moisture from the Gulf of
Mexico. This initial return of low level moisture will not be
overly rich, due to the last cold front having scoured the
Continental shelf just offshore, with richest moisture being
suppressed over the central Gulf of Mexico and Bay of Campeche.
Though delayed, better moisture will surge north into the area
later Thursday into Friday, as noted by Richer Theta-E values
within the surface- boundary layer. Southwest flow aloft ahead of
an amplifying western U.S. Trough will hold a fairly Stout
eml(capping inversion) overhead through Thursday. However, as the
lead shortwave lifts out across the state, the eml should continue
to gradually weaken. This first shortwave will mainly result in
increasing cloudiness, especially in the mid to upper levels on
Thursday. The low level warm advection will result in both warmer
and more humid low temperatures, with high temperatures each day
warming to between 75 and 85 degrees.
Another shortwave will be right on the tail of the first shortwave
disturbance heading into Thursday night and Friday and is notably
stronger. Ascent associated with this second perturbation will
lead to some weakening of the eml with increasing Theta-E advection
and isentropic ascent aloft lending to low convective chances
this period. Mid level lapse rates will be steep enough for charge
distribution and isolated to scattered elevated storms. If
moisture recovers faster than currently expected both at the
surface and mid levels, then a few stronger elevated storms with
small hail may occur, but it does not appear to be the case at
There will be a lull between these initial shortwaves and a much
more vigorous mid level disturbance that arrives later this
weekend. Low chances for non-severe thunderstorms will continue
Saturday, as we await the strong mid level disturbance Saturday
night and Sunday. The 00z runs of gefs/eps ensembles and operational
GFS/European models all seem to have a pretty good handle with
regard to strength and timing of the actual kinematic features and
dynamics, though moisture and the thermodynamic environmental set
up remain uncertain, especially with regard to the strength of the
eml (cap) over the area. The system and associated strong surface
cold front are still on schedule to arrive in the midnight to
midday Sunday timeframe. We will continue advertising the potential
for strong storms with gusty winds, hail, and frequent lightning
during this time frame and hope to get a better handle on the
thermodynamic environment as it evolves and we move closer to the
weekend. With any severe weather threat uncertain, we do encourage
everyone to pay close attention to future forecasts with regard
to this system with outdoor weekend activities likely in full
swing. Otherwise, it is likely that many areas will see their high
temperatures Sunday morning in the 70s, with brisk winds and slow
falling temperatures late in the day into Sunday evening.
Previous medium range model runs, especially the European/eps
ensembles, had mid level energy cutting off early next week.
However, recent 00z runs have indicated more of a progressive
mid level trough in alignment with the GFS/gefs forecasts. This
means this system will exit the area Sunday night into Monday with
cooler temperatures returning to the region and northwest flow
aloft over the Southern Plains.
Preliminary point temps/pops...
Dallas-ft. Worth 76 53 81 57 81 / 0 0 0 0 0
Waco 78 47 83 54 83 / 0 0 0 0 5
Paris 73 47 78 52 79 / 0 0 0 0 0
Denton 76 48 81 53 81 / 0 0 0 0 0
McKinney 75 47 79 52 80 / 0 0 0 0 0
Dallas 77 54 81 58 81 / 0 0 0 0 0
Terrell 75 46 81 53 83 / 0 0 0 0 0
Corsicana 76 49 80 56 81 / 0 0 0 0 5
Temple 78 48 82 57 82 / 0 0 0 0 5
Mineral Wells 77 47 82 52 81 / 0 0 0 0 0