Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Albuquerque nm
1053 am MST Tuesday Dec 10 2013
18z taf cycle
VFR conditions expected all locations through period. Middle level
dry slot moving across northern third of the forecast area with
clear skies while scattered-broken high clouds will stream from west to
east generally along and south of Interstate 40. Gusty west to
southwest surface winds will favor the central mountains and
eastern plains this afternoon. A back door cold front to move into
the northeast plains by around 03z and through the remainder of
the Eastern Plain by 12z. Not sure of low clouds at this point but
cant rule out a possible surge into the northeast and possibly to
Tucumcari early Wednesday morning.
Previous discussion...312 am MST Tuesday Dec 10 2013...
under northwest flow aloft a warming trend will commence today through
Thursday. An exception will be Wednesday in the east when there
will be cooling compared to todays readings due to a brief back
door frontal intrusion.
An upper level low pressure system currently off the coast of the
upper Baja California peninsula is prognosticated to weaken into an open wave as it
shifts east northeastward across nm Thursday through Friday morning. The
NAM...ECMWF...Canadian and to a lesser extent the UKMET all depict
this system developing a tap of moisture off the eastern Pacific
and producing precipitation mainly over western and southern areas
as it crosses Thursday and Thursday night. However...the GFS shunts the
moisture eastward into Texas before it can lift northward into nm.
Went with the model consensus on probability of precipitation...which favors the SW and S
central mountains for wetting precipitation at this time. Temperatures
should be warm enough for rain showers and very high elevation
snow showers until snow levels drop to valley bottoms with the
passage of a Pacific cold front from the west Thursday night. The
cold front may reach south central and east central areas late
enough Thursday night to prevent temperatures from reaching
freezing in some lower elevation locations like Ruidoso...Roswell
and Tucumcari. If the bullish European model (ecmwf) and Canadian models are
correct...then the western and southern mountains could squeeze
out a few inches of snow accumulation.
Another upper level trough is prognosticated to dive southeastward across
nm Friday and Friday night keeping showers in the forecast. This
secondary system looks fairly short on moisture...so we are not
looking for much accumulation with it. However...temperatures
should plummet again as a cold front dives southward through the
forecast area Friday and Friday night.
Dry northwest flow aloft should re-establish Sunday with a warming trend
that could shift high temperatures to near and above normal across
the forecast area by Monday.
the combination of a strong middle level dry intrusion and cold airmass
brought very low dewpoints to the surface yesterday afternoon and
overnight. Residual low dewpoints will continue the next couple of
days although the airmass will modify some and the middle level dry
intrusion will weaken. Went below guidance on dewpoints in a few areas
due to placement of the middle level dry intrusion. Temperatures will
warm pretty much areawide today but still remain below normal.
Humidity values will lower most areas and expecting teens readings
across the southwest. Surface winds will increase across the east
and over the higher ridges of the central mountains but lower across the
western half compared to yesterday. Mixing heights will be lower
than normal thanks to Post cold frontal inversion effects so
ventilation rates will generally be poor across the area today. Mixing
heights will remain low on Wednesday and vent rates will generally
be a little lower due to less transport winds across the east.
Models are still picking up on the weak low that is currently
spinning off the northern Baja California coast and is cut off from the main
upper flow. They bring the closed low over Arizona on Thursday and
then open it up over New Mexico Thursday night into Friday. Models
continue to vary on the amount of moisture advection or flow ahead
of the wave and during the wave passage. The NAM and European model (ecmwf) are much
more bullish in increasing dewpoints and thus portray some
measurable precipitation. The GFS remains the drier of the models.
All of the models have trended drier the past few runs. Decided to
go with more of the NAM dewpoint blend so have pretty high humidity
values across western and southern areas Thursday with some holdover
drier pockets across the north and east. Similar humidity values are
expected on Friday as the system passes over. High temperatures on
average should be near normal both Thursday and Friday across the
area although pockets of above and below normal readings between 3
to 5 degrees exist in the forecast.
Models have lowered mixing heights some on Thursday compared to the
past few runs although improve values across the southwest due to
the approaching low. Mixing heights will increase pretty much
areawide on Friday due to the low passage. Ventilation rates will
follow a similar trend with areawide improvement on Friday.
Thursday/S surface winds look to be on the lighter side but
increase...especially across the southern half on Friday. Did
increase the wind forecast across the south on Friday as the upper
flow is depicted to be rather strong by all of the models and mixing
heights look to be near to above normal.
The longer range models are still showing a drier northwest flow
over the area during the weekend and show the pattern lasting into
early next week. The flow appears to be moderately strong and will
most likely usher in a stronger middle level dry intrusion. Lowered
dewpoints slightly and raised winds along the Central Mountain chain and
areas to the Lee of the central mountains the one fly in the ointment
lies with the type of flow. Typically a disturbance moves through
under such a flow after a few days so will be watching that closely.
Ventilation will lower during the weekend but suspect rates will end
up higher than what the current gridded forecast is showing. Thus
can see more fair areas showing up. Especially where the northwest
flow gradient is strongest such as between Farmington to
Albuquerque to Clovis.