Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pocatello Idaho
109 PM MST Friday Nov 21 2014
Short term...tonight through Monday.
Moist Pacific storm system still on track to start affecting
southeast Idaho tonight through Saturday night. Winter storm
warnings remain in effect for the central mountains and eastern
Highlands with advisories in effect for the Lost River pahsimeroi
area and south Central Highlands above 6 thousand feet. Snow
should begin around midnight in the central mountains and spread
east quickly overnight. Expect hazardous mountain travel tonight
through Saturday evening. Think the Snake River Plain will see
mostly rain although could see a brief period of snow at onset
early Saturday morning but will change to rain. Idaho Falls and
Rexburg may see up to an inch in the morning before changing over.
Have issued a Wind Advisory for the eastern Magic Valley and Snake
River Plain Saturday with strong southerly winds expected ahead of
the cold front shifting to a west to southwest direction after the
cold front moves through Saturday afternoon and remaining strong.
Precipitation will taper off west to east Saturday afternoon and
evening as flow aloft transitions to a northwesterly direction.
Several weak waves in this flow will keep period of light snow
going through Sunday night with most accumulations likely in the
eastern Highlands near the Wyoming border. Will have drier
conditions Monday. Snow levels will drop to valley floors early
Saturday evening after the heaviest precipitation has moved east
so not expecting significant snowfall in the Snake River Plain.
Temperatures should be below seasonal normals Sunday and Monday
after some milder conditions ahead of the cold front Saturday.
Long term...Monday night through Friday. We are not making too
many changes to the forecast heading into next week. The GFS and
European model (ecmwf) are trying to build a stronger ridge in for midweek...which
bring a pretty dry pattern for eastern Idaho except for some
mountain snow Near Island park. If you look at the ensemble
forecasts...they depict an overall weaker ridge and northwest
flow. Some of the individual forecasts within the ensembles
actually look like the European model (ecmwf) a few days ago and its forecast for
very cold conditions. While we thought that might be too
extreme...it just shows the amount of confidence or in this case
lack of it on how things will play out heading into Thanksgiving.
We did try and dry the southern half of eastern Idaho out a bit on
Tuesday. Other than that...we keep rain and snow in the forecast
for most of the central and eastern mountains all the way through.
For the rest of the area...chances are much lower for now. Bottom
line...if you have plans to be traveling or outdoors over the next
few days make sure you check the latest forecasts. The picture
will definitely become more clear over the next few days. Keyes
Aviation...conditions will start to deteriorate late this evening
and overnight as our advertised storm moves into eastern Idaho. We
should ceilings drop to at least MVFR closer to midnight. Expect
MVFR/IFR conditions between 7-11z/midnight-4am at all taf sites.
Kbyi will likely not see snowfall at all and will be rain throughout
the event. Kpih and kida may initially see snow at the very
beginning of it...transitioning to rain before 15z/8am as warm air
pushes quickly up the plain. Ksun will try to switch to a mix
between 13-15z/7-9am. They will likely change back to snow showers
in the late afternoon as cold air starts to move back into the
central mountains...although most of the moisture may be out of
there by then. Winds will be a big story as well...especially
affecting the plain taf sites. Sustained winds of 20-35kts and gusts
of 40-50kts are forecast starting near sunrise and lasting through
the day. Keyes
Wind Advisory from 8 am to 8 PM MST Saturday idz017-020-021.
Winter Storm Warning from 5 am to 11 PM MST Saturday
Winter Weather Advisory from 5 am to 11 PM MST Saturday above
6000 feet for the idz022-032.
Winter Storm Warning from 11 PM this evening to 5 PM MST