Flood Watch 3, NWS Pocatello, ID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
306 AM MST MON FEB 15 2016

.UPDATE...TO ADD FLOODING RISK FROM STRONG SNOWMELT IN EASTERN
MAGIC VALLEY AND SNAKE RIVER PLAIN.  MESSICK

&&

.PREV DISCUSSION... /ISSUED 246 AM MST MON FEB 15 2016/

SHORT TERM...TODAY THROUGH WED NIGHT. WEAK UPPER LEVEL TROUGH IS
RIDING THROUGH THE LONGWAVE RIDGING AND IS STILL ABLE TO GENERATE
PRECIPITATION TODAY AND INTO THIS EVENING...SO WILL CONTINUE THE
WINTER WEATHER ADVISORY FOR THE ELEVATIONS PREVIOUSLY FORECASTED
IN THE SAME ZONES. THE NORTHWESTERLY FLOW CONTINUES TO GENERATE
PRECIPITATION EVEN BEYOND THIS EVENING...MAINLY IN THE UPPER SNAKE
HIGHLANDS. THERE IS A BRIEF COOL-DOWN...BUT A STRONGER TROUGH
ENTERS THE FORECAST AREA LATE WED NIGHT. THIS TROUGH IS ALSO
BRINGING MILD AIR AND EVEN MORE MOISTURE. WILL NOT DO ANYTHING
FORMAL WITH THIS STORM...BUT WILL HIGHLIGHT IN SOCIAL MEDIA. THIS
STORM WILL ALSO HAVE HIGH SNOW LEVELS--EVEN THE WED NIGHT LOWS ARE
ABOVE FREEZING FOR MUCH OF THE EASTERN MAGIC VALLEY AND SNAKE
RIVER PLAIN. RAIN WILL CONTINUE AT MOST ELEVATIONS BELOW 6000
FEET...AND A RAIN AND SNOW MIX 6000 TO 8000 FEET. PARTIAL CLEARING TUE
NIGHT WILL ALLOW TEMPERATURES EVEN IN THE SNAKE RIVER PLAIN TO GET
BELOW FREEZING ONCE AGAIN.

THE OTHER FACTOR TODAY WITH THE PRESENT TROUGH IS THE WIND. WIND
ADVISORY IS CURRENTLY OUT...AND SINCE THERE WILL BE AREAS GETTING
ABOVE 26KT...HAVE DECIDED TO LEAVE THIS OUT...ALTHOUGH SOME ZONES
WILL HAVE AN EASIER TIME REACHING THE THRESHOLD. WOULD SAY THOUGH
THAT IT IS A MARGINAL EVENT. THE 700MB WIND IS STRONG BUT NOT
ALIGNED CORRECTLY...COLD AIR ADVECTION IS FAIRLY WEEK...AND
INSTABILITY ALSO SOMEWHAT WEAK. WIND CONTINUES BREEZY FOR
TUE...WEAKENS EVEN MORE FOR WED.

LONG TERM...THURSDAY THROUGH NEXT MONDAY. BOTH THE GFS AND ECMWF
DRIVE A FAIRLY MOIST AND ENERGETIC PAC STORM SYSTEM EAST THROUGH THE
REGION THURSDAY WITH FALLING SNOW LEVELS AND MODEST SNOW
ACCUMULATIONS FOR THE MOUNTAINS. THE MODELS WERE ALSO SUPPORTING
ADVISORY LEVEL WIND SPEEDS THROUGHOUT THE SNAKE RIVER PLAIN. THE
SYSTEM PASSES QUICKLY EAST BY FRIDAY AS THE NEXT PAC LOW TAKES SHAPE
OFF THE NW COAST. THE EVOLUTION OF THIS LOW AND RESULTING
PRECIPITATION ACROSS SE IDAHO AS DEPICTED BY THE ECMWF AND GFS
DIFFER EARLY SATURDAY AND THOSE DIFFERENCES CONTINUE INTO MONDAY AS
YET ANOTHER PAC SYSTEM EJECTS INTO THE REGION. GIVEN THE VARYING
MODEL TIMING AND STORM TRACKS HAVE DECIDED TO TRY AND NUDGE THE
GOING FORECAST TOWARD A BLEND OF THE TWO AFOREMENTIONED MODEL
SOLUTIONS WHICH REALLY WASHES OUT ANY PARTICULAR DETAIL. WILL LIKELY
CONTINUE THIS TECHNIQUE UNTIL WE GET BETTER MODEL AGREEMENT. DAYTIME
TEMPS REMAIN FAIRLY MILD THROUGH THE PERIOD WITH ALL THE ACTIVITY.
HUSTON

&&

AVIATION...EARLY MORNING SATELLITE IMAGERY WAS SHOWING A BROAD FLAT
RIDGE POSITIONED ALONG THE PAC NW COAST WITH A STEADY STREAM OF PAC
MOISTURE SPILLING OVER THE RIDGE INTO SRN IDAHO. OBSERVATIONS AND
MODEL CROSS SECTIONS HIGHLIGHT A LAYER OF LOW LEVEL MOISTURE PRESENT
WITH THE SNAKE RIVER PLAIN (IFR/MVFR CIGS) WHICH THE MODELS SLOWLY
DISSIPATE AT KBYI AND KPIH LATE THIS AFTERNOON/EVE WHILE KIDA
REMAINS FAIRLY WELL ENTRENCHED THROUGHOUT THE FORECAST PERIOD. KSUN
REMAINS FAIRLY DRY UNDER VFR PASSING HIGH CLOUDS THROUGHOUT THE
PERIOD. HUSTON

&&

.HYDROLOGY...NOHRSC MELTING FORECAST FOR LOWER SNAKE RIVER PLAIN
AND EASTERN MAGIC VALLEY INDICATES A RISK OF AREAL FLOODING DUE TO
THE MELTING. A FLOOD WATCH WILL BE ISSUED FOR THIS. MESSICK

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH THIS EVENING FOR IDZ017-021.

WIND ADVISORY FROM 9 AM THIS MORNING TO 7 PM MST THIS EVENING
FOR IDZ017-020-021.

WINTER WEATHER ADVISORY UNTIL 8 PM MST THIS EVENING FOR IDZ019-
023-025.

&&