Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Fort Worth Texas
1127 PM CST Monday Mar 2 2015
No major changes other to indicate vlifr/LIFR visibilities/ceilings with
-dz/fog persisting through at least 15z at all airports. Surface ridge
axis continues to drifting slowly east away into East Texas/Upper Texas
Gulf Coast through midday Tuesday helping a weak warm front surge
north. The weak warm air advection and overrunning over the top of cold and moist
soils will be slow to erode and likely not until almost midday
Tuesday or after...at which time increasing southerly flow 10-15
kts and a warming boundary layer help ceilings slowly rise into
IFR...then briefly into MVFR during the afternoon hours.
Confidence on trends after 18z Tuesday aren't very high...though
mixing from approaching upper level trough should improve
conditions Tuesday afternoon. With winds settling some Tuesday
evening...have brought conditions back IFR conditions shortly
after 00z Wednesday ahead of an approaching cold front.
With such emphasis on the first 12-18 hours of the forecast...have
decided to leave the cold frontal passage out of the 24-30 hour dfw
taf for now...but next few tafs will likely include a frontal
passage sometime before daybreak Wednesday. Afterward...challenges
on a turnover to winter precipitation during the day Wednesday
will present more challenges to aviators Wednesday and Wednesday night.
visibilities continue to deteriorate across all of North Texas
with easterly winds now prevailing. Expanded the dense fog
advisory to all of our County Warning Area through 10am Tuesday.
Previous discussion... /issued 327 PM CST Monday Mar 2 2015/
A long wave trough extends from the Hudson Bay vortex
southwestward into the Desert Southwest where it will remain
anchored for a few days while the rest of the trough moves east.
The trough is positively tilted and will kick a surface cyclone
across the Central Plains on Tuesday and send another strong cold
front through north and central Texas.
Winds will veer overnight as low pressure deepens in the Lee of
The Rockies. A warm front near the Texas coast will begin moving
north with local winds veering southeast. The return of low level
warm advection will result in scattered light rain...areas of fog
overnight and temperatures holding near steady or slowly warming
Tuesday will be much warmer and breezy but skies should remain
mostly cloudy. Scattered showers are expected area wide most of
the day. Instability for thunderstorms will be best over the
northeast counties during the afternoon. Instability will weaken
in the evening...thus thunderstorm activity will become more
isolated overnight as the cold front moves across the Red River
shortly after midnight.
We feel the NAM series is too slow with wednesdays cold front and
have sided with the GFS/European model (ecmwf) model solutions for this forecast.
The front will work through the County Warning Area Wednesday morning with
temperatures holding steady or slowly falling once it passes and
strong north winds the rest of the day. Lift along the front and
forcing for ascent from above will keep showers/rain going most of
the day. As the depth of the cold deepens...rain will transition
to a wintry mix of freezing rain and sleet...then to all sleet.
There may be some snow mixed it as the precipitation starts to
end...but it should not be the predominant precipitation type for
this event. We expect this transition to begin along the Red River
around middle morning Wednesday...across the metroplex shortly after
midday and around Waco/Killeen/Palestine by sunset.
The main area of our concern is the southeast portion of the
County Warning Area...generally southeast of a Comanche to Canton line with focus
on Waco/Killeen to Athens/Palestine...where we think sleet could
accumulate up to 1/2 inch and freezing rain up to 1/10 inch. This
is due to a strong frontogenesis signature around 700mb and the
right- rear entrance region of a 200 knot upper jet over this
region. We will be issuing a special statement with this package
to highlight the potential for sleet/ice to cause hazardous
impacts Wednesday night into Thursday. This is an evolving system
and the actual location and magnitude of the sleet and ice will
likely change some as new data is received.
As for the metroplex...once temperatures fall to freezing or
below...precipitation would begin to accumulate on mix-masters..
overpasses and bridges...followed by roadways shortly afterward.
The intensity of the sleet and duration will govern how fast
impacts develop during the afternoon/evening commute. If around
one-tenth or more of sleet accumulates by dark...then impacts
would last through the Thursday morning commute.
The precipitation will be ending over the southeast counties by
midday Thursday. Otherwise...it will remain dry and cold into
Friday. The cold air will move east late Friday with winds
returning to the south. This will bring warmer temperatures for
the weekend and a slight chance of rain over the southeast
counties. Another upper trough may pass across the region on
Sunday which could bring slightly cooler temperatures for Sunday
and Monday. 75
Preliminary point temps/pops...
Dallas-ft. Worth, Texas 40 65 39 39 27 / 30 40 60 80 50
Waco, Texas 41 69 48 48 28 / 30 30 50 80 70
Paris, Texas 39 63 38 40 24 / 30 60 60 80 60
Denton, Texas 40 65 35 37 25 / 30 40 60 70 50
McKinney, Texas 40 64 37 38 25 / 30 50 60 80 50
Dallas, Texas 40 67 40 41 27 / 30 40 60 80 50
Terrell, Texas 40 67 42 43 27 / 30 50 60 80 60
Corsicana, Texas 41 68 46 47 28 / 30 40 60 80 70
Temple, Texas 40 68 50 50 28 / 30 30 40 70 70
Mineral Wells, Texas 37 69 35 37 26 / 30 30 60 60 50
dense fog advisory until 10 am CST Tuesday for txz091>095-