Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus64 kfwd 222047 

Area forecast discussion
National Weather Service Fort Worth Texas
247 PM CST Wed Feb 22 2017

clear and tranquil weather will prevail again tonight with light
southerly winds and temperatures dropping into the 50s. These
southerly winds will increase during the day on Thursday to 15 to
25 mph as a surface low develops in the Lee of The Rockies across
Kansas. As the low level cyclone translates across the plains
during the day, it will cause winds to become more southwesterly
and drag a ill-defined dryline toward the I-35 corridor by late
afternoon. Behind the dryline temperatures are poised to soar
into the upper 80s and lower 90s and put relative humidity below
20 percent which will dry out fine fuels despite the recent
rainfalls. Wind speeds look to weaken just enough behind the
dryline to preclude critical fire weather conditions, but we will
still need to highlight an elevated risk of grass fires. To the
east of the dry line, it will not be quite as warm with
temperatures reaching the mid 80s, but dfw looks like it will
break its daily record high of 86 set in 1933, while Waco should
stay below their record of 89. Dfw will assuredly add another day
to the most 80 degree highs in the winter months - a record that
was set today at 11 (breaking the record of 10 days set in
1908-09 & 2005-06 seasons).

The record heat will come to an end Thursday night as a cold front
quietly slides through the region during the overnight hours.
Modest northwesterly winds will prevail Friday with continued
sunny skies, but cold advection will keep high temperatures in
the 60s and 70s. Very dry air and breezy northwest winds will again
promote an elevated risk of grass fires in the afternoon hours
over the entire area. Cold advection will continue into the
nighttime hours with lows dropping into the 30s for most areas.
Although a few spots will flirt with freezing in the northwest
zones, it appears winds will stay up enough to keep most areas
freeze and frost-free. Pleasant weather Saturday with light winds
and sunny skies with highs in the the upper 50s and lower 60s.

There are some divergences in the computer models from Sunday and
beyond which i'll address a little later, but there is actually
really good agreement in the main feature which is the ejection of
an upper trough across the plains on Tuesday. Furthermore, all
models indicate unseasonably high low level moisture with
dewpoints in the 60s over the region Tuesday. Given the agreement
and pattern recognition, there is a fair amount of confidence in
saying there will be a dryline and a potential for severe
convection in the region Tuesday. Right now the uncertainty is
where the dry line will set up and whether it will be west or east
of the I-35 corridor. Obviously a western position would bring
more of the area into the fold for severe weather, while an
eastern position would be more typical of early Spring and limit
any severe threat to our eastern counties. Models seemingly are
favoring a western dryline position, but this doesn't quite align
with climatology and lowers confidence in delineating a risk area
at this time. What is certain is that there will be ample wind
shear and sufficient instability in place ahead of the dry line so
it warrants our attention over the next few days.

The model differences and most uncertain part of the forecast is
actually the Sunday and Monday period. Strong south winds return
to the area on Sunday which will bring moisture screaming
northward ahead of shortwave trough and weak front. While deep
layer shear is more than ample, instability looks very limited but
it is not zero. For now, believe that moisture will not return
fast enough to provide the instability for a severe risk, but
there will be a chance of rain/storms along the front.
Confidence is also very low when determining where the front
stalls, and therefore will favor a blend of solutions that bring
the weak front into and through the area Sunday night. This would
result in generally cloudy conditions Monday and Monday night
with a chance of showers as moisture again surges northward ahead
of the main upper trough.

Beyond the Tuesday system, it appears we will see a cool-down to
near normal. Looking even further out, we may not be done with a
widespread freeze either. A lot of the long range operational and
ensembles guidance is suggesting a pattern change that would help
Arctic air pool across central and western Canada. The majority of
the guidance prevails zonal flow in the southern branch of the
jet (a theme of the last several weeks) which would tend to keep
this Arctic air well northeast of the region. However there may be
an increased risk of below normal temperatures and possible
freezing conditions around the second week of March when one the
longwave troughs move across the country and bring a piece of this
air southward. This kind of cold air intrusion would be fairly
normal for the time of year, as our last freeze usually doesn't
occur until mid to late March. So despite the very warm winter and
record heat lately, gardeners certainly don't have the all-clear
to start their annuals just yet.



/issued 1134 am CST Wed Feb 22 2017/
/18z tafs/

Only minor challenges are expected with wind speeds/gusts, as we
move into Thursday with VFR conditions prevailing throughout the

A weak surface trough was located west of I-35. South-southeast-south-southwest winds less
than 10 knots will prevail through mid morning Thursday. Lee
cyclogenesis will increase well to the northwest on Thursday, as a
strong shortwave disturbance lifts east across the central
rockies and plains. This process combined with strong thermal
mixing by midday Thursday will result in gusty S winds 15-25

A cold front will shift winds northwest by early Friday, but that is well
beyond the 24-30 hours and will be addressed in later forecasts.



Preliminary point temps/pops...
Dallas-ft. Worth 57 87 54 71 40 / 0 0 5 0 0
Waco 52 85 53 75 37 / 0 0 5 5 0
Paris 53 82 54 71 37 / 0 0 5 5 0
Denton 53 87 50 68 34 / 0 0 0 0 0
McKinney 52 84 52 70 37 / 0 0 5 5 0
Dallas 58 87 55 71 41 / 0 0 5 5 0
Terrell 54 84 55 73 38 / 0 0 5 5 0
Corsicana 56 85 55 75 40 / 0 0 5 5 0
Temple 54 86 54 79 36 / 0 0 5 5 0
Mineral Wells 51 90 48 70 32 / 0 0 0 0 0


Forward watches/warnings/advisories...

National Weather Service Glossary of Abbreviations