Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 020544
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1145 PM MDT SAT AUG 1 2015

UPDATE...ADDED 06Z AVIATION DISCUSSION.

.SHORT TERM...TONIGHT THROUGH SUNDAY (ISSUED AT 231 PM MDT)

WIDESPREAD HIGH PRESSURE EXPECTED TO CONTINUE ACROSS THE FORECAST
AREA. WARM TEMPERATURES WILL CONTINUE...ESPECIALLY ACROSS THE
NORTHERN BASINS WHERE VALUES WILL INCH CLOSER TOWARDS THE CENTURY
MARK.

CURRENT PATTERN REMAINS SUPPORTIVE OF LIGHT WIND THROUGH THE
FORECAST PERIOD AS WELL. A FEW HIGH CLOUDS COULD MOVE INTO THE
SOUTHERN PORTION OF THE FORECAST AREA SUNDAY AFTERNOON AS A WAVE
SLOWLY PROGRESSES TOWARDS THE STATE. MODELS CONTINUE TO SLOW THE
PROGRESS OF THIS WAVE. CURRENT PRECIPITATION FORECAST FOR SUNDAY
AFTERNOON MAY BE PESSIMISTIC BASED ON MOST RECENT MODEL
SOLUTIONS...BUT LEFT A FEW ISOLATED SHOWERS ACROSS THE
AREA...ESPECIALLY IN THE MID TO LATE AFTERNOON.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY.

THE SHORTWAVE TROUGH FROM THE GREAT BASIN IS STILL EXPECTED TO MOVE
INTO WYOMING FROM SUNDAY NIGHT INTO MONDAY...ALTHOUGH ALL OF THE
MODELS SEEM TO HAVE SLOWED IT DOWN SOMEWHAT COMPARED TO YESTERDAYS
MODEL RUN.  THE RESULT WILL BE LESS OF A CHANCE OF PRECIPITATION
SUNDAY EVENING...WITH MORE OF A CONCENTRATION ON MONDAY...ESPECIALLY
DURING THE AFTERNOON AND EVENING HOURS.  SOUTHWEST WY WILL BE
IMPACTED FIRST...THEN THE REST OF CENTRAL AND SOUTHERN WY.  AT THIS
TIME EXPECTING GOOD MOISTURE AND MODERATE INSTABILITY TO BRING HEAVY
RAIN AND GUSTY OUTFLOW WIND WITH THE THUNDERSTORMS.  AS THE SYSTEM
PROGRESSES TO THE NORTHEAST...A BOUNDARY SHOULD DEVELOP ACROSS
CENTRAL WY WITH MOIST UNSTABLE AIR TO THE NORTH...AND DRIER WINDY
CONDITIONS TO THE SOUTH.  TUESDAY THEN WILL LIKELY SEE THE
CONVECTIVE ACTIVITY ACROSS NORTHERN WY.

ANOTHER WEAK SHORTWAVE TROUGH FROM THE PACIFIC THEN APPROACHES
WESTERN WY WED AFTERNOON AND EVENING...WITH THE GFS BEING THE
STRONGEST OF THE MEDIUM-RANGE MODELS.  HAVE GONE MORE OF A BLEND
WITH THE CHANCES OF PRECIPITATION...AND LIKE THE PREVIOUS
SHIFT...LEFT IN GUSTY WIND AS THE MAIN THREAT FROM THE
THUNDERSTORMS.  THE GENERAL PATTERN FROM MONDAY THROUGH WEDNESDAY
WILL KEEP TEMPERATURES NEAR OR BELOW NORMAL...WITH AN OBVIOUS
ENHANCEMENT FOR ABOVE NORMAL PRECIPITATION.

THURSDAY THROUGH SATURDAY LOOKS TO BE SLIGHTLY WARMER AND DRIER THAN
THE BEGINNING OF THE WEEK.  THURSDAY AFTERNOON AND EVENING SHOULD BE
FAIRLY DRY...EXCEPT FOR NE WY WITH SOME RESIDUAL INSTABILITY AND
MOISTURE FROM THE SHORTWAVE TROUGH.  BOTH THE GFS AND ECMWF INDICATE
ANOTHER SHORTWAVE TROUGH FROM THE PACIFIC MOVING INTO ID/MT/WY LATE
SATURDAY...AGAIN INCREASING THE CHANCE FOR SHOWERS AND
THUNDERSTORMS...BUT ALSO INCREASING THE WIND THROUGH CENTRAL AND
SOUTHERN WY.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WITH MOSTLY UNLIMITED CIGS WILL PREVAIL THROUGH THE
PERIOD WITH GENERALLY LIGHT WIND LESS THAN 10KTS.  THE PREVAILING
SFC WIND WILL BECOME N-NE SUNDAY AFTERNOON.

AN UPPER LEVEL DISTURBANCE WILL LIFT NORTH ACROSS THE GREAT BASIN
SUNDAY NIGHT...SPREADING INCREASING MID-LEVEL MOISTURE...SCT-BKN
FL130-150...AND A FEW SHOWERS VCNTY AND SOUTH OF INTERSTATE 80 AFTER
06Z MONDAY.

&&

.FIRE WEATHER...

WARM AND DRY CONDITIONS WILL CONTINUE THROUGH SUNDAY MORNING...WITH
THE SLIGHT OPPORTUNITY FOR A FEW MOUNTAIN SHOWERS AND THUNDERSTORMS
SUNDAY AFTERNOON. AN APPROACHING WAVE FROM THE DESERT SOUTHWEST
CONTINUES TO LOOK LIKE THE NEXT WEATHER PRODUCING SYSTEM...THOUGH
MODELS CONTINUE TO DELAY ITS ARRIVAL INTO THE STATE. MONDAY
AFTERNOON NOW LOOKS FAIRLY FAVORABLE FOR SHOWERS AND THUNDERSTORMS
ASSOCIATED WITH THIS SYSTEM. MEANWHILE...THOUGH WARM AND DRY
CONDITIONS WILL PERSIST OTHERWISE WITH HUMIDITY IN THE LOW
TEENS...WINDS THROUGH MONDAY MORNING DO NOT LOOK SUPPORTIVE FOR
CRITICAL FIRE BEHAVIOR ACROSS THE AREA. WINDS DO GET STRONGER MONDAY
AFTERNOON...ESPECIALLY ACROSS SOUTHERN WYOMING. HOWEVER...MOST
LOCATIONS WHERE THE STRONGER WINDS ARE LOCATED WILL BE DEALING WITH
THE ARRIVAL OF THE AFOREMENTIONED WAVE OF LOW PRESSURE ELIMINATING
THE CONCERN FOR LOW HUMIDITY LEVELS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...BRANHAM
LONG TERM...MCDONALD
AVIATION...AEM
FIRE WEATHER...BRANHAM


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