Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 071946

Area Forecast Discussion
National Weather Service Pocatello ID
146 PM MDT Tue Apr 7 2020

.SHORT TERM...Tonight through Thursday night. An upper low
continues to spin off the California coast with a deformation zone
set up over southeastern Idaho tonight. This zone will serve as a
focal point for showers until around midnight. Thunderstorm
chances are fairly weak, though there is some instability to work
with. Drier and warmer weather is on the way for the rest of the
week with temperatures approaching 70 degrees in the Magic Valley
and Lower Snake Plain by Thursday. Hinsberger

After another warm, dry, and gorgeous day Fri, showers should
increase Fri night and esp Sat as a shortwave trough drops out of
Canada into the northern Rockies. Continued mild temps Sat may help
support some thunderstorms as well, although we hold off at least
another day on including them in the forecast. Precip chances Sat
will be greatest along the MT border and in the eastern highlands,
trending lower/more isolated as you head south and west across the
Snake Plain and toward Burley. Models show reasonable agreement at
this time. Sat night and Sun, the main trough drops into the Plains
leaving us with much colder temps post-cold front. In fact, highs
may only top out in the 40s Sun! Model guidance seems to be trending
drier post-front, but we didn`t want to completely let go of a
chance of showers just yet, predominantly snow showers if they
occur. The drying trend bodes well as far as reducing any potential
snow accumulations and associated impacts from Sat night
this juncture we are not expecting significant accumulations. Model
guidance diverges Mon and Tues, as does forecast confidence. SE
Idaho will reside in a potentially active storm track on the western
edge of a massive longwave trough over the central/eastern USA, with
some potential for precip depending on the finer scale evolution of
any shortwaves or disturbances during this period. Cooler temps will
likely hold on as well. - KSmith


Today will be a day of transition as SE Idaho is wedged between a
low pressure storm system over CA, and another over central Canada.
A fairly dry, westerly flow just off the sfc should keep most of the
Magic Valley, Snake Plain, and Central Mntns dry (KSUN), while some
showers and isolated t-storms (courtesy of the CA low) are expected
this afternoon/eve across the southern/eastern highlands (KDIJ).
KBYI/KPIH/KIDA look to reside right along the western edge of where
precip is possible. Some high-res guidance sources toss a shower or
storm their way while others don`t, so maintained VCSH with the
thought that best chance for thunder should reside further
south/east. Overall instability and shower coverage are expected to
be less than yesterday, so a direct hit to a given terminal isn`t
very likely and precluded upgrading anyone from VCSH. Initial
shower/storm development is expected to hold off until after 20z,
increasing further after 21z. HREF ensemble supports a quick end to
showers by 03z. Otherwise, moderate SW winds are expected at
KPIH/KIDA, but aligning fairly well with the major runways to
minimize crosswinds. We MAY see diurnal SE winds at KSUN trend into
the SW later this afternoon per MOS, and the flow should be out of
the west everywhere just off the sfc. All guidance sources keep the
low-levels too dry for fog/low stratus issues tonight, and given a
predominantly dry day today for most locations and only very brief
issues at KPIH/KIDA last night following significant rainfall, see
no strong reason to argue with this. Looking ahead to Wed and Thurs,
mostly sunny skies and VFR conditions are expected, with similar or
lighter diurnal winds. Great weather for aviation! Forecast
confidence is moderate to high right though Thurs. - KSmith



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