Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 211939
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
139 PM MDT THU MAY 21 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY.

LITTLE CHANGES MADE TO THE FORECAST. LOW PRESSURE ALONG THE
CENTRAL CALIFORNIA COAST CONTINUES TO PUMP MOISTURE INTO THE
REGION. SHOWERS AND A FEW THUNDERSTORMS HAVE DEVELOPED ACROSS THE
MOUNTAINS AND HIGHLANDS. SOME STORMS WILL MOVE OFF THE TERRAIN AND
INTO THE MAGIC VALLEY AND SNAKE PLAIN INTO THIS EVENING. MUCH BUT
PROBABLY NOT ALL OF THE ACTIVITY WILL DISSIPATE OVERNIGHT. THE LOW
WILL MOVE ACROSS SOUTHERN CALIFORNIA ON FRIDAY. BECAUSE THE LOW IS
SOMEWHAT CLOSER TO THE AREA...EXPECT BETTER COVERAGE FOR SHOWERS
AND THUNDERSTORMS FRIDAY AFTERNOON. THE LOW WILL MOVE INTO
SOUTHERN UTAH FRIDAY NIGHT AND MODELS SHOW SOME SHOWERS
PINWHEELING AROUND THE LOW. AS A RESULT EXPECT COVERAGE TO LESSEN
FRIDAY NIGHT BUT ISOLATED TO SCATTERED SHOWERS WILL PERSIST
THROUGH THE NIGHT. THE LOW WILL STALL OVER SOUTHERN UTAH ON
SATURDAY. SHOWERS AND THUNDERSTORMS LOOK LIKELY FOR SATURDAY
BECAUSE OF THE POSITION OF THE LOW. THE LOW MOVES INTO WESTERN
COLORADO ON SUNDAY...BUT THE MODELS TRY TO BRING IN SLIGHTLY DRIER
AIR FROM THE NORTH. THIS WILL CUT BACK ON THE COVERAGE SOMEWHAT ON
SUNDAY...BUT STILL GOOD CHANCES FOR SHOWERS AND THUNDERSTORMS. NOT
EXPECTING MUCH SEVERE WEATHER OVER THE NEXT FEW DAYS. MAIN THREATS
WILL BE LOCALLY HEAVY RAIN WITH SOME PONDING OF WATER POSSIBLE
ALONG WITH SMALL HAIL AND GUSTY WINDS.

VALLE

.LONG TERM...SUN NIGHT THROUGH NEXT THU NIGHT. MOIST AND UNSTABLE
AIRMASS IS NOT GOING MUCH OF ANYWHERE. LOW PRESSURE TO THE SOUTH IS
EXCHANGED FOR A LOW DROPPING DOWN FROM THE CANADIAN COAST ON MON.
THIS MAY GIVE THE ACTUAL HOLIDAY OF MEMORIAL DAY A BREAK FROM THE
SHOWERS AND THUNDERSTORMS AS THE INCOMING UPPER LEVEL LOW BRINGS
BRIEF WESTERLY FLOW...BUT THE LOW IS ALREADY FAIRLY CLOSE TO THE GEM
STATE AND ITS PROXIMITY MAY STILL PROVIDE ENOUGH UPPER LEVEL SUPPORT
TO MAKE LITTLE DIFFERENCE. THE NEW UPPER LOW IS HANDLED DIFFERENTLY
BY THE ECMWF AND THE GFS. THE ECMWF SEEMS IS A LESS PROGRESSIVE
SOLUTION WITH THE LOW SITTING AND SPINNING OVER THE INLAND PACIFIC
NORTHWEST FOR MOST OF THE REST OF THE PERIOD AFTER MON. THE GFS
MOVES IT THROUGH AS AN OPEN WAVE TROUGH ON WED. SO THE GFS HAS SOME
HOPE OF CLEARING OUT IN THE LAST 24 HOURS OF THE FORECAST...BUT THE
ECMWF IS KNOWN FOR ITS BETTER HANDLING OF CLOSED LOWS LIKE THIS
DURING THE SPRING MONTHS. SO HAVE TRIED TO BLEND THE TWO SOLUTIONS.
NEVERTHELESS...THERE IS A THREAT OF SHOWERS PRETTY MUCH EVERY
DAY...IT COMES DOWN TO WHETHER OR NOT IT IS A SLIGHT CHANCE OR
BORDERING ON LIKELY. TEMPERATURES STAYING WITH MILD OVERNIGHT LOWS
DUE TO CLOUD COVER AND THE WARM AIR MASS KEEPING AFTERNOON HIGHS
JUST ABOVE NORMAL. IF THE GFS IS CORRECT...THE TROUGH PASSAGE IS
STRONG ENOUGH THAT THERE COULD BE A WIND EVENT ON WED...BUT WILL
MONITOR FOR NOW TO SEE HOW STABLE THIS GFS SOLUTION IS. MESSICK

&&

.AVIATION...STABILITY FORECASTS INDICATE AN AFTER-00Z START TO THE
STRONGEST CONVECTION...SO HAVE DELAYED THE ONSET OF VCTS FROM
PREVIOUS THINKING. DO NOT EXPECT SHOWERS TO BE AS WIDESPREAD BECAUSE
OF THE LATER START TO THE CONVECTION. SHOWERS SHOULD REDEVELOP
DURING THE LATE MORNING ON FRI FOR ANOTHER ROUND OF -TSRA. MESSICK

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$


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