Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Albuquerque nm
456 PM MST Wednesday Dec 11 2013
00z taf cycle
VFR ceilings and viz through 15z Thursday morning.. cloud deck at or above
broken/ovc050 moving north and east toward Interstate 40 from 15z
Onward...with clouds reaching the Rio Grande Valley around 21z.
Areas of rain and snow producing excursions to IFR from the Arizona
line to the Continental Divide continuing beyond 00z. East of the
Rio Grande...ceilings remaining at or above broken/ovc100 with any showers
mainly south of Interstate 40. Vcsh in taf weather groups
place holding for most likely period of shower onset.
Previous discussion...302 PM MST Wednesday Dec 11 2013...
most of the high clouds have been steered out of New
Mexico this afternoon. Warming trend is ongoing in the central to
western zones...but the eastern plains of nm had a setback with
last night's frontal intrusion. Winds have already veered
southerly at Clayton...Las Vegas...and Raton...a sign that a Lee
side surface trough will be redeveloping with warm air advection
and some down sloping soon to follow. In addition...the Pacific
upper low is encroaching upon the Baja California peninsula. Ahead of the
low...southwesterlies aloft will draw in some warmer and more
moist air into Chihuahua and New Mexico late tonight. Some high
clouds will spread over the southeastern half of the state with
remaining areas remaining mostly clear. Temperatures will be near
to only slightly below average tonight.
As the upper low moves into western Arizona...clouds and middle level
moisture will continue to increase in the diffluent flow ahead of
it. Best upper forcing...saturation...and condensation will occur
in the southern tier of the state outside of the forecast
area...but still some precipitation is expected to infiltrate the
southwestern half of the abq County Warning Area. NAM and local
7.5km WRF models have aggressively raised quantitative precipitation forecast and numerical pop
guidance. Frontogenetical forcing is not all that high due to
relatively warm temperatures in the maritime-originated low...and
best isentropic lift does not appear to arrive into the forecast
area until Thursday night. However...a quick glance at lifted
indices reveals that some middle level instability may be
present...and this could account for the NAM/wrf's higher quantitative precipitation forecast.
Have taken the bait and increased probability of precipitation both Thursday and Thursday
night. Despite increasing cloudiness...temperatures are expected
to rise several degrees higher Thursday afternoon amidst surface
winds largely from the south and southwest.
As alluded to earlier...better isentropic lift arrives into the
southwestern half of the forecast area Thursday night as the low
works into western nm. The low will be filling in aloft and
weakening before daybreak Friday...but still a long enough
duration of forcing should provide some wetting precipitation.
Snow levels remain fairly high Thursday with most accumulation
impacts relegated to the high terrain above 8000 feet...but levels
should drop to valley floors and the plains by Thursday night and
A brisk northwesterly flow aloft will be left in the wake of the
departing trough on Friday. Have left some lingering probability of precipitation...but
subsidence may overcome any orographic forcing or remnant middle
level saturation...so confidence is fairly low for precipitation
Friday. Winds will also be a concern...mostly in the Central
Highlands and eastern plains where the gradient aloft will attempt
to sync with a stronger surface gradient left in place by the
exiting surface low.
A secondary trough aloft will then sweep southeastward Friday
night and possibly a third one Saturday into Saturday night. The
former will have potential to drive some spotty northern mountain
showers...but less optimism for the latter. Northwest flow aloft
will stay intact through the first half of next week...gradually
losing strength each day. It now looks like the transition will be
made to a longer wave trough pattern that would once again open
the door to Arctic air.
no significant changes made to the gridded forecast. Still
looking at a Baja California originating storm system Thursday and Friday.
Models are trending more bullish for precipitation so chances have
been increased. Liquid water amounts have also been increased.
Thus...chances have been increased for wetting precipitation
southwest and west central areas.
Cloud cover will go on the increase as surface dew points increase
from south to north on Thursday. A dry pocket should still exist
over the northern mountains and have lower humidity depicted
there...especially across the northeast plains where some teens will
be possible. Mixing heights still look to be pretty low for this
time of year most areas so ventilation rates dont come out very
good. Some improvement is expected across large portions of zone 109
The Pacific trough will finish its sweep over the area on Friday.
Mixing heights will increase and transport winds will increase most
areas. Improving ventilation will result although poor readings
still show up across the northern half or so. Northwest winds will
certainly increase and have some gustier readings across central and
eastern portions of the forecast area...especially to the Lee of the
Sandia/Manzano Mountains. A more northerly flow will develop Friday
night and give way to cooler temperatures. As mentioned
above...precipitation chances look more likely with the system
passage and favor western and southern areas.
A trailing piece of Pacific energy is depicted to move over the
state on Saturday. This disturbance should provide additional cloud
cover and reinforce cooler conditions. Models are painting a few
light showers but dont believe that will amount to much. High temperatures
Saturday afternoon should range between 5 to 10 degrees below
Weather models still show a drier northwest flow Sunday through
Tuesday. It appears as though the main middle level dry intrusion
should stay west and south but cant rule out much drier air pushing
in from those locations as we get closer to the time period.
Ventilation forecasting will be rather tricky. Current models
suggest less than ideal ventilation conditions although suspect the
rates will increase across some areas as we get closer to the
period. Especially over the higher terrain and areas to the Lee of
the central mountains. Both European model (ecmwf) and GFS show at least moderate
wind speeds aloft. GFS is a bit stronger than European model (ecmwf) however.
Confidence is at least moderate for a drier northwest flow with
gradual warming temperatures during this period. Above normal
temperatures are expected Monday and Tuesday.
The long range models show a flattening flow or near zonal flow over
the state Wednesday and ultimately a southwest flow later in the
week as a Pacific trough approaches the area. Will be monitoring
model trends real closely as this trough has the potential of being
pretty vigorous with another robust back door cold front. If current
trends offer a glimpse into the future...late next week and weekend
could be quite unsettled. Climatology would also give credence to
this pattern. It should be mentioned...ventilation would most likely
improve ahead and during the system passage.