Weather Service Report


016 
FXUS65 KBOI 261514
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
914 AM MDT Fri May 26 2017

.DISCUSSION...Upper low now east of the forecast area, but enough
residual moisture left to support some showers and thunderstorms
over the Idaho areas this afternoon. Cold pool aloft, along with
high sun angle giving some surface heating, results in reasonable
instability. Northerly flow aloft on back side of low means that 
storms should move north to south, but shear is weak, so do not 
expect storms to be very organized or strong. Northerly flow aloft
also supports breezy conditions in the Snake River valley.
Instability diminishes quickly this evening as the low continues 
to drift eastward and ridging aloft builds in from the west.
&&

.AVIATION...Mostly VFR with scattered MVFR showers, and possibly a 
thunderstorm, across central and southern Idaho, ending rapidly with 
sunset. Surface winds: Generally 10 kts or less, with some gusts to 
25 kts near stronger showers/thunderstorms. Winds aloft near 10 kft 
msl: North/Northwest 10-15 kts. 
&&

.PREV DISCUSSION...
SHORT TERM...At 2 AM MDT upper low was located over central Idaho.
Showers were mainly in south-central Idaho, with a separate area of 
fewer showers in the west central Idaho mountains.  The low and 
showers will shift slowly east today, the low gradually weakening. 
Instability due to cold pool aloft will provide a slight chance of 
afternoon and evening thunderstorms especially near the low center. 
Clearing from west to east tonight and continued cool under 
northerly flow aloft ahead of the next upper ridge currently off the 
coast.  Saturday will be sunny and warmer as the upper ridge edges 
inland.  Breezy northwest winds in the Snake Basin this afternoon, 
lighter winds elsewhere.  Light winds in all areas tonight and 
Saturday.

LONG TERM...Saturday night through Friday...An upper level ridge is 
the dominant feature through the beginning of the extended forecast. 
Some moisture can be seen in the models pushing up over the ridge, 
but most of this remains out of our CWA. The next upper level Low 
can be seen offshore Tuesday afternoon and begins to press inland 
later that evening. Timing of this feature and associated 
precipitation differs among the models. The GFS continues to be the 
faster model compared to the ECMWF. The GFS starts to bring 
precipitation in as early as Wednesday morning while the ECMWF holds 
off until Wednesday afternoon. Because of this timing issue, left a 
mention of precipitation in the forecast, but confidence on timing 
remains minimal. Temperatures continue to climb through the 
beginning of the extended forecast under the influence of the upper 
level ridge with Tuesday looking to be the warmest. Temperatures 
begin to cool off a bit after this as the upper low begins to track 
into our area, but still remain above normal. 

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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DISCUSSION...TB
AVIATION.....EP
PREV SHORT TERM...LC
PREV LONG TERM....JC

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