Flash Flood Watch 7, NWS Boise, ID

Area Forecast Discussion
National Weather Service Boise ID
303 AM MDT Sun Oct 30 2016

.SHORT TERM...Short wave trough with showers and isolated
thunderstorms moved across eastern Oregon and western and central
Idaho last evening, and as of 3 AM MDT was moving north of our
CWA.  Stronger wave rotating around a Pacific low 40/132 will
spread moisture into our CWA from the southwest and south this
afternoon while a surface cold front comes in from the west.
Rain showers will increase rapidly from the south in Idaho
this afternoon.  The air mass will become unstable enough for
thunderstorms, and the incoming front will provide extra lift,
for a chance of strong thunderstorms with heavy rain and gusty
winds.  Heaviest rains will extend from Owyhee County northeast
through the Boise Mountains and West Central Idaho Mountains
this afternoon and evening.  This includes the Pioneer Fire
area.  We will therefore issue a flash flood watch for the Boise
Mountains this afternoon and evening.  Also, southwest winds
will increase to advisory speeds along and behind the cold front
in Harney and Malheur Counties in Oregon and the Owyhee Mountains
in idaho this afternoon and evening, and we will post a wind
advisory for it.  Temperatures will be a few degrees lower today
except in the western Magic Valley where highs 65 to 70 are
expected before the cold front gets there.  Highs Monday will be
a few degrees lower than today except about 10 degrees lower in
the western Magic Valley.

.LONG TERM...Monday night through Saturday...Current model runs
remain in fairly good agreement through the extended period, with
some minor differences in timing and placement of systems as they
move through the flow. A weak shortwave will move over the forecast
area Monday night and Tuesday with precipitation spreading over the
region Monday night and decreasing from west to east Tuesday
afternoon. Mostly dry conditions over the forecast area Tuesday
night as the shortwave trough continues to shift to the east. Dry
conditions over the forecast area Wednesday through Friday as a
ridge of high pressure builds over the forecast area. Models still
hinting that a weak shortwave will ride over the top of the ridge
Thursday, but latest model trends keep any precipitation with this
system to the north of the forecast area. For the weekend, models
begin to diverge on the next upper level trough that will move into
the Pacific Northwest. Latest model trends have slowed down the
timing of this trough and precipitation moving into the forecast
area, but the GFS still wants to spread precipitation into southeast
Oregon Saturday afternoon. With low confidence in the models at this
time will leave the near-climo pops for Saturday and make
adjustments in later forecasts when confidence increases.

&&

.AVIATION...Mostly VFR this morning, with areas of mountain valley
IFR/LIFR conditions in fog and low stratus, especially at KBKE and
KMYL. This afternoon lowering ceilings with numerous showers
developing over the area. As showers develop mountains will become
obscured along with areas of MVFR and local IFR conditions. Cannot
rule out thunderstorms this afternoon into this evening. Surface
winds variable 12 knots or less this morning, becoming east to south
5-15 knots with gusts of 15-25 knots this afternoon, expect south
and west of a KBNO-KREO line with southerly winds 20-30 knots and
gusts of 25-35 knots. Winds aloft south to southwest 25-40 knots up
through 10K feet MSL.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Flash Flood watch from this afternoon through late tonight
     IDZ013.
     Wind advisory from 2 PM this afternoon to 9 PM MDT this evening
     IDZ029.
OR...Wind advisory from 2 PM MDT /1 PM PDT/ this afternoon to 9 PM
     MDT / 8 PM PDT/ this evening ORZ061-063..

&&

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SHORT TERM...LC
LONG TERM....JA
AVIATION.....JA