Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Flagstaff Arizona
340 PM MST Wednesday Mar 12 2014
Synopsis...a low pressure system over southern Nevada central
California will slowly move east across Arizona late Thursday
bringing showers and a few thunderstorms to the region. By Friday
showers will gradually clear from west to east through the day as
the low moves into New Mexico and a high pressure ridge builds back
along the West Coast. Dry weather conditions and above normal
temperatures return by Saturday and last into next week. On Saturday
and Sunday...expect strong and gusty northerly winds to develop as a
system drops south across The Four Corners region into New Mexico.
Discussion...water vapor imagery shows a closed low over southern
Nevada central California this afternoon. Forecast models bring
this system across Arizona Thursday afternoon into Friday morning.
The snow levels will be around 7000 feet however graupel showers may
be seen down to around 6000 feet on Friday. Any snow accumulation
will be above 7000 feet as the cold core of the low passes across
the area during the day Friday. Decided to go closer to the European model (ecmwf)
timing on bringing the system across Arizona. The latest 18z run on the
GFS has jumped the arrival of the low by around 8 hours which would
put the upper low center east of Flagstaff by around 5am Friday
morning. Given the uncertainty in the GFS and this latest shift in
the timing...no more than 24 to 36 hours out from the arrival of the
system...leaves some questions into the usefulness of the GFS
forecast for the Thursday Friday system. The timing used in the
gridded and zone forecasts has precipitation beginning after midnight early
Friday morning lingering through Friday afternoon before ending.
Some locations above 7000 feet may receive maybe an inch with most
places seeing either rain showers below 6000 feet...snow above 7000
feet ... mix with rapid melting in places between 6000 and
Saturday-Sunday...a upper level low drops south through The Four
Corners and into New Mexico on Saturday and lingers over southern
New Mexico West Texas through Sunday. This will bring windy north to
northeast winds across northern Arizona through this time period.
Monday through Wednesday...warm temperatures and low humidity levels 15
percent and below can be expected. Winds will be breezy during the
afternoon hours aw well.
Aviation...for the 00z package...cloud cover will gradually
increase over the next 24 hours...with isolated -shra/-shsn possible
mainly from kigm-kflg-krqe northward after 06z. Expect generally VFR
conditions but isolated MVFR conditions in snow showers above 7000 feet
elevation. Winds light and variable. After 18z...scattered rain showers/shsn with
isolated thunderstorms and rain possible across northern Arizona...especially higher terrain
areas. Expect generally VFR conditions but isolated IFR/MVFR conditions
in snow showers above 6500-7000 feet elevation. Winds becoming
sw5-15 kts. Aviation discussion not updated for amendments.
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