Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 190911

Area Forecast Discussion
National Weather Service Pocatello ID
311 AM MDT Sun Mar 19 2017

.SHORT TERM...Today through Tue night. Low amplitude long wave
pattern at 500mb means that shortwaves will dominate the weather
pattern and thus the forecast may change considerably from day to
day. There is a low passing through that has brought some isolated
late night thunderstorms to the Malta vicinity, and this may
continue during the morning hours, and then intensify throughout
the forecast area for this afternoon and evening. in the post-
frontal regime, there may be some breezy conditions but that looks
like about it outside of the thunderstorms. Greater cloud cover
and the colder air will end the record-setting warmth many
locations had on Sat. A brief let up late tonight before yet
another shortwave passes through. The main storm track is to the
north, and thus the bulk of the precipitation is in the central
Idaho mountains and in the ID-MT border region and Tetons. There
is a fairly strong gradient in the Probability of Precipitation
(PoP) from north to south for Mon through Tue night. Stronger
sunshine and unstable air could also be a trigger for thunderstorm
activity in the afternoons and evenings, if a break in the
cloudiness develops. On Tue night, the possible major storm of the
week starts making its approach, bringing abundant rain fall and
the coldest air of this period, with snow levels lowering to at
least 6000 ft. As previously mentioned, being on the southern side
of the storm track means mild temperatures, but the cloud cover
means no records being set. Messick

.LONG TERM...Wednesday through Sunday. The GFS and ECMWF appear to
be coming into better agreement with this model cycle as the next
incoming PAC trough undergoes a split as it moves onshore Wednesday
and Wednesday night resulting in much less precipitation across SE
Idaho. Residual moisture clips the NRN and SE portions of the area
Thursday as each respective branch of the split works east. An
amplified short-wave ridge builds over the area Thursday night for
drier conditions as the next upstream PAC low moves into the NW
coastal waters. Both models show the leading edge of the associated
precipitation shield working into the CNTRL mountains by Friday
afternoon (a little faster than yesterdays progs) and the remainder
of SE Idaho Friday night for a likely mention of showers. Snow
levels will likely range near 6000 feet MSL resulting in valley rain
and mountain snowfall overnight and through the day Saturday.
Decreasing showers and colder temperatures are anticipated Saturday
night into Sunday morning as the storm system progresses east of the
region and the next upstream storm system takes shape off the NW
coast. There should be a couple of breezy days Wednesday and again
Friday while temperatures remain at or above normal through the
period. Huston

.AVIATION...Early morning satellite and radar imagery was showing a
disturbance lifting NE through the area with attending rain and
higher mountain snow working through the region. CIGS associated
with all this activity have remained VFR at the terminal locations
with mountain obscurations likely in the higher terrain. Numerical
models show improving conditions this morning behind the exiting
disturbance followed by a second round of convection and VFR CIGS
this afternoon and evening associated with another passing
disturbance. Huston

.HYDROLOGY...5 Local flood advisories: in lower Blaine County,
western Bingham County, northeast Caribou County, eastern Oneida
County, and central Bear Lake County. The Portneuf River in
Pocatello did in fact go above minor flood stage and should
continue, with a possibility of going to the next level within the
next week. Finally, many locations continue under a flood watch
with continued snow melt, that may be exacerbated by a wet period
for the next 4 days. Messick

Flood Watch through Monday morning for IDZ017-019-021>025-031.

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