Freeze Warning 1, NWS Pocatello, ID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
235 AM MDT TUE MAY 10 2016

.SHORT TERM...TODAY THROUGH THU NIGHT. TROUGH WILL EXIT
TONIGHT...BUT STILL ENOUGH MOISTURE AND INSTABILITY TO GENERATE
SHOWERS AND AFTERNOON THUNDERSTORMS...MAINLY THE EASTERN HALF OF
THE FORECAST AREA...BUT OTHER PARTS AS WELL...JUST MORE LIGHT
SLIGHT CHANCE IMPACT. AFTER TONIGHT...AN UPPER LEVEL RIDGE
STRONGLY BUILDS IN...AND PUSHES THE FRINGE OF THE SHOWER AND
THUNDERSTORM TRACK TO THE ID-MT BORDER REGION AND A SMALL AREA IN
THE CENTRAL ID MOUNTAINS. NOT AS MUCH INSTABILITY AND SO THREAT
IS VERY LOW. WOULD NOT SAY ZERO AS THERE IS SOME NEGATIVE LIFTED
INDEX IN THAT AREA AND CAPE ABOVE 300 J/K INDICATED EVEN BY THE
GFS...WHICH IS USUALLY HARDER TO GET CONVECTION. NOT LOOKING AT A
REPEAT TO THE WIND SITUATION OF YESTERDAY...BUT THERE IS A
SIGNIFICANT WIND SHIFT AS NORTHERLY FLOW INCREASES ALOFT. RIGHT
NOW...IT APPEARS THAT THE NORTH WIND STAYS BELOW 9KT OVER THE
AMERICAN FALLS RESERVOIR...SO NO LAKE WIND ADVISORY WILL BE
NEEDED. THE COLD AIR ADVECTION IN THE NORTH WIND WILL KEEP
TEMPERATURES COLD...EVEN COLDER THAN YESTERDAY. BUT THE NORTH WIND
SHUTS DOWN WED AND STRONG WARMING UNDER THE RIDGE AT 9 TO 11 DEG F
PER DAY FOR BOTH WED AND THU.

THESE LEAVES THE MOST IMPACTFUL WEATHER FOR LAST. THERE IS
EXPECTED TO BE SUB-FREEZING TEMPERATURES IN THE POPULATED
I-15/US-20 CORRIDOR FROM FORT HALL NORTHWARD TONIGHT WITH THE COLD
NORTHERLY WIND ALL DAY. THE WORST WILL BE SEEN IN THE UPPER SNAKE
PLAIN...INCLUDING IDAHO FALLS/AMMON AND REXBURG. IT WILL ALSO BE
WIDESPREAD...EVEN IN POPULATED AREAS...OF THE EASTERN HIGHLAND
ZONES AND PLACES LIKE SODA SPRINGS...SWAN VALLEY...SAINT
ANTHONY...AND ASHTON.

.LONG TERM...FRIDAY THROUGH TUESDAY...THE END OF THE WEEK
STARTS OF WARM AND DAY UNDER A HIGH PRESSURE RIDGE. FORECAST MODELS
ARE IN PRETTY GOOD AGREEMENT REGARDING THE OVERALL SYNOPTIC PATTERN
THIS FORECAST PERIOD. UNFORTUNATLY WHEN WE NEED THEM TO AGREE
SATURDAY WITH THE NEXT APPROACHING WEATHER SYSTEM...THEY START TO
DISAGREE A BIT. BOTH GFS AND ECMWF BRING MOISTURE AND THE UPPER LOW
INTO THE REGION AND THUS MORE OR LESS AN EQUAL CHANCE FOR RAIN AND
THUNDERSTORMS...HOWEVER THEIR TIMING AND PLACEMENT FOR HEAVIEST
ACTIVITY DIFFERS. THE ECMWF MODELS PLACES STRONGEST ACTIVITY MORE TO
THE NORTH AND CLEARS THE FIRST MAIN ROUND OF ACTIVITY EARLY SUNDAY
MORNING. GFS SOLUTION KEEPS ALMOST ALL OF SE IDAHO RAINY THROUGH
SUNDAY AND INTO MONDAY. THE FORECAST IS MORE IN LINE WITH THE GFS
SOLUTION ATTM WITH A TREND TOWARD HIGHER POPS IN THE EASTERN
HIGHLANDS BY MONDAY. A RATHER SIGNIFICANT COOL OFF EXPECTED FOR
SUNDAY WITH TEMPERATURES EXPECTED TO DROP 10 TO 15 DEGREES ACROSS
OUR REGION. THE RELATIVELY COOLER AIR IS EXPECTED TO STICK AROUND
THE FIRST HALF OF NEXT WEEK. NP/MESSICK

&&

.AVIATION...ISOLATED SHOWERS EXPECTED TODAY AT ALL
LOCATIONS...THUNDERSTORMS NOT LIKELY. INCREASING WINDS FROM THE
NORTH AT IDA MID TO LATE MORNING IN EXCESS OF 15 KNOTS WHICH WILL
PERSIST THROUGH EVENING. THIS TREND ALSO EXPECTED AT PIH JUST NOT
QUITE AS STRONG. BYI WINDS SHOULD BE FROM THE WEST TO NORTHWEST AT
LESS THAN 15 KNOTS. DIURNAL FLOW AT SUN. CEILINGS FORECAST AT VFR
STATUS FOR ALL 4 SITES EXCEPT IN SHORT PERIODS OF ANY HEAVY RAINFALL
THE NEXT 24 HOURS. NP/MESSICK

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR
IDZ019>021-023-025.

&&