NWS FTW LONG TERM... /Issued 400 AM CST Wed Dec 4 2024/
/Thursday Night through Tuesday/Modest low level warm advection will commence atop a cold surface
airmass late Thursday night with cloud cover increasing rapidly
from the southwest during the overnight hours. This will likely
result in a fairly hefty gradient in low temperatures from the
upper 20s in the northeast where skies remain clear to near 40 in
the southwest. Areas of light rain will likely develop across the
Big Bend region into the Big Country by daybreak Friday, although
there is still some uncertainty in the coverage of precipitation
through Friday. This is partly due to the very dry airmass in
place prior to the warm moist advection spreading north. We`ll
have some generally low PoPs across our southwest spreading north
through the day Friday. All of this is in response to an upper low
digging through the Desert Southwest and into northwest Mexico.
As this low digs south, a secondary upstream shortwave will help
amplify the pattern a bit and kick this low out across the
Southern Plains. Timing of this secondary shortwave will play a
factor in the timing of best precipitation chances through the
weekend across Central and North Texas. It now looks more likely
that ample moisture will be close enough to the region for most of
North and Central Texas to see rainfall. Ensemble cluster analysis
has trended wetter with about 65% of the members, including a
sizable chunk of the ECMWF members, showing at least one shot of
widespread rain late Friday through early Sunday. The
aforementioned timing uncertainty remains, but we`ve trended the
forecast a little wetter with this package. The consensus of the
guidance shows that the best rain chances will coincide with the
strongest height falls spreading into the Southern Plains which
looks like it will occur late Saturday into Saturday night, so
we`ve nudged the NBM PoPs upward through this timeframe, although
some adjustments will likely be needed over the next 48 hours.
Rainfall amounts have also been adjusted upward with widespread
totals of 0.5 to 1.5 inches and higher end amounts approaching 3
inches in our far southeast counties through Sunday. While this
will be a strongly forced system, a lack of any surface based or
substantial elevated instability will limit any potential for
severe weather. Clearing should occur late Sunday with another
cold front spreading south through the Plains Monday night.Our next system bares watching as things turn colder Monday night with a stronger cold front and more precip.