Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 062017
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
217 PM MDT FRI MAY 6 2016

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT. DEEP UPPER LOW OVER
SOUTHWEST STATES REMAINS IN PLACE. MOISTURE ROTATING AROUND LOW
ACROSS SOUTHEAST IDAHO FOR AN ACTIVE DAY OF CONVECTION. BROAD AREA
OF SHOWERS AND ISOLATED THUNDERSTORMS MOVING NORTHWEST THROUGH
FORECAST AREA THIS AFTERNOON. HAVE SEEN SOME LOCALLY HEAVY
DOWNPOURS WITH THIS REGION PER RADAR AND GUSTY WINDS APPROACHING
50 MPH PER OBSERVATION AND SPOTTER REPORTS. SECOND MORE POTENT
AREA OF CONVECTION ONGOING ACROSS NORTHERN UTAH. SOUTHERN IDAHO
DESTABILIZING AGAIN WITH EARLY AFTERNOON SUN AND LIKELY TO BECOME
THE ACTIVE AREA LATER THIS AFTERNOON AND EARLY EVENING AS THE UTAH
STORMS ADVECT NORTH AND INTO FAVORABLE INFLOW IN REGION OF
NORTHEAST SURFACE GRADIENT. AIR MASS FAVORABLE FOR SMALL HAIL AND
GUSTY WINDS WITH POTENTIAL FOR A FEW STORMS TO REACH SEVERE
CRITERIA. SOME CONVECTION LIKELY TO SURVIVE PAST SUNSET THROUGH
OVERNIGHT BUT WEAKENED GIVEN LOSS OF DIURNAL HEATING. OTHER THREAT
FOR TODAY REMAINS THE STRONG WINDS THROUGH THE SNAKE PLAIN
ASSOCIATED WITH THE NORTHEAST SURFACE GRADIENT. STRONGEST WINDS
ACROSS THE ARCO DESERT AND MAGIC VALLEY BUT SOME HINT OF STRONGER
WINDS IN THE VICINITY OF THE AMERICAN FALLS RESERVOIR. CONDITIONS
MARGINAL ACROSS THE RESERVOIR CURRENTLY BUT WILL LET THE LAKE WIND
ADVISORY CONTINUE AS PLANNED.

UPPER LOW CONTINUES TO ROTATE EAST THROUGH THE GREAT BASIN
SATURDAY WITH MORE CONVECTION ROTATING INTO EAST IDAHO. BIGGER
THREAT OF FLOODING WITH THE PRECIP ON SATURDAY WITH THE GROUND
ALREADY MOISTENED FROM TODAYS ACTIVITY. WILL HOLD OFF ON FLASH
FLOOD WATCH FOR NOW TO SEE HOW THE EVENING AND OVERNIGHT
CONVECTION PLAYS OUT. UPPER LOW SHIFTS INTO WYOMING/COLORADO WITH
A NORTHEAST CONFLUENT FLOW OVER EAST IDAHO. WILL SEE SOME
INSTABILITY LINGERING INTO SUNDAY AND BEST POTENTIAL FOR
CONVECTION LIKELY OVER HIGHER TERRAIN SUNDAY. DMH

.LONG TERM...SUN NIGHT THROUGH NEXT FRI NIGHT. AS THE UPPER LOW THAT
CAME UP FROM THE SOUTHERN BASIN DEPARTS...A LOW FROM CANADA MOVES IN
TO THE REGION. THUS THE FOCUS OF PRECIPITATION DURING THIS EXTENDED
PERIOD IS THE MT-ID AND ID-WY BORDERS WITH THE SOUTHWEST CORNER OF
THE FORECAST AREA...THE MAGIC VALLEY AND SOUTH CENTRAL
HIGHLANDS...LEAST AFFECTED. THERE IS A POTENTIAL WIND EVENT AS THE
LOW MAKES ITS CLOSEST APPROACH ON MON AFTERNOON/EVENING...AS THE
SOUTHERN SIDE OF THE LOW HAS A SPEED MAX PUSHING OVERHEAD IN THE
SOUTHERN HALF OF THE FORECAST AREA DURING THAT TIME. THERE MAY BE A
PERIOD OR TWO WHERE CENTRAL AND EASTERN IDAHO WILL ACTUALLY BE
DRY...BUT MAINLY THERE IS A THREAT SOMEWHERE EACH DAY. SUN NIGHT/MON
IS BY FAR THE WETTEST 24 HOURS. AFTER TUE EVENING...THE TREND IS FOR
CLOUDIER AND WETTER CONDITIONS THAN PREVIOUS THINKING. HAVE
INCREASED SLIGHTLY TO CONTAIN BORDER ISSUES WITH NEIGHBORING
OFFICES. MESSICK


&&

.AVIATION...GUSTY EASTERLY AND SOUTHEASTERLY WIND...A FAIRLY UNUSUAL
DIRECTION FOR ALL THE AIRDROMES IN EASTERN IDAHO. THIS IS DUE TO A
LOW MOVING IN FROM THE SOUTH. IT HAS DEVELOPED SEVERAL LINES OF
-TSRA AND HAS THE POTENTIAL FOR HAIL AND STRONG WIND. CONDITIONS
EXPECTED TO CALM DOWN LATE TONIGHT. ANOTHER ROUND OF UNSTABLE MOIST
AIR IS EXPECTED SAT AFTERNOON. KPIH AND KSUN ARE AT SOME RISK FOR
MARGINAL VFR CONDITIONS...BUT HAVE KEPT IT OUT FOR NOW. KBYI IS MORE
LIKELY TO SEE THEM DURING THE LATE NIGHT AND EARLY MORNING HOURS.
HAVE TRIED TO TIME THE ARRIVAL OF -TSRA WITH USE OF THE HRRR
MODEL GUIDANCE. MESSICK


&&

.PIH WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 6 PM MDT THIS EVENING FOR IDZ021.

&&

$$


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