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Area forecast discussion 
National Weather Service Pocatello Idaho
155 PM MST Thursday Jan 29 2015

Short term...tonight through Sunday. Satellite imagery was showing
a fairly well defined split flow across the west with the main storm
track arching north through western Canada and a weaker secondary flow
dipping south into Baja California. Embedded in the weaker secondary flow were
two well defined low pressure off the SW California
coast and a second weaker feature over Eureka California. The models
have been fairly consistent with the idea of lifting the low off the
SW coast inland across Southern California Friday as the weaker
circulation to the north is drawn southward into the main low.
Accompanying the main low will be a fairly broad plume of
sub-tropical moisture which is expected to produce widespread valley
rain and mountain snow across the 4-corners region while the northern
fringe of the plume extends as far north as Bear Lake late
tonight/Friday morning. Thus southern Idaho will remain fairly dry with
the exception of valley fog and low clouds redeveloping overnight.
Starting Friday afternoon and continuing through Friday night...the
ridge across the northwest states settles across southern Idaho as a weak
disturbance works into western Canada resulting in another night of low
clouds and fog. By Saturday...the Canadian disturbance digs southeast
through Montana and eventually across Nebraska by Sunday morning...
a path which remains well to our NE. A secondary disturbance follows
early Sunday taking a more southerly track through the northern rockies
with attending snow spreading across mainly the central and eastern Idaho
mountains Sunday afternoon and continuing into Monday. Storm total
accumulations on this storm may approach advisory levels across the
eastern Highlands so we will continue to monitor this system as it
develops. Huston

Long term...Sunday night through Thursday. We continue to see some
fluctuations in GFS and European model (ecmwf) for the early part of next week. Both
show idea of precipitation occurring across our northern areas for
sure with perhaps some passing showers farther south. The extent of
that continues to change if you compared all of the model runs each
day. Interestingly enough...if you look at the ensemble forecasts a
trend toward most of the precipitation that might fall just across
the north is emerging. In fact the least in the past
24 hours indicate the pattern may develop even more to the north and
leave US a lot drier. That is something we will have to watch.
Anyway...we are keeping with the idea of rain and snow continuing
and higher chances/amounts across the central and eastern Highlands.
It does appear the ridge rebounds later next week and pretty
strongly...which is shown in all of the data we are seeing. The
forecast will keep trending for a low chance of showers across the
central and eastern Highlands and pretty dry for the rest of eastern
Idaho. With the ridge rebounding we should see a return to inversion
conditions although we might see that confined to the upper plain
and some mountain valleys. Keyes

Aviation...the aviation forecast has certainly changed in the past
24 hours and is becoming one of much lower confidence as fog and low
clouds become more spotty. The northerly flow has really cleared out
much of the snake plain. There is still some fog and low clouds
along the edges of the plain and surrounding feeder valleys. Kida
has cleared out and is VFR. Based on the latest forecast and
trends...they may stay VFR even though some high and middle level
clouds increase except for a brief period this evening. We may see a
brief period of stratus or fog reform after sunset until around
midnight. Kbyi and kpih are seeing MVFR/IFR as the flow is banking
moisture up against the edge of the plain. Conditions should improve
for both airports but also see a brief period of lower clouds/fog
returning this evening to around midnight. For once...ksun may prove
trickiest of all as the fog/stratus deck can be seen just to the
south. It looks like might be thinning but we also are awaiting the
wind to switch to upvalley and see if it quickly comes back into the
area. The current taf has that occurring. When the wind switches
back to the northwest conditions will return to VFR. If the threat
of fog/stratus is more widespread than our current thinking or just
happens to linger at an Airport for a extended period...IFR and
possibly LIFR weather would result. Keyes

Pih watches/warnings/advisories...none.


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