Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 280544
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1145 PM MDT WED MAY 27 2015

UPDATE...ADDED 06Z AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH THURSDAY (ISSUED AT 215 PM MDT)

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL GENERALLY SUBSIDE
ONCE AGAIN THIS EVENING MAINLY EAST OF THE DIVIDE. SCATTERED SHOWERS
WILL CONTINUE OVERNIGHT ACROSS WESTERN AND SOUTHERN PORTIONS...AS
WELL AS ACROSS JOHNSON COUNTY. THE MAIN THREAT FROM THESE SHOWERS
AND STORMS REMAINS LOCALLY HEAVY RAIN. CHANCES FOR PRECIPITATION
WILL INCREASE AFTER 12Z THURSDAY...BECOMING WIDESPREAD BY 18Z.
LOCALLY HEAVY RAIN WILL CONTINUE TO BE THE MAIN THREAT FROM THIS
ACTIVITY.

ABUNDANT MOISTURE...BOTH LOW AND MID LEVEL...STEEP LOW LEVEL LAPSE
RATES...AND A TROUGH AXIS WILL BE IN PLACE ACROSS THE AREA THURSDAY.
A LACK OF DIABATIC HEATING AND BULK SHEAR OF 15-20 KTS SHOULD KEEP
ANY STORMS THURSDAY FROM BECOMING TOO STRONG. THUS...STRONG GUSTY
WINDS AND HAIL ARE NOT EXPECTED.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY NIGHT

MORE ACTIVE WEATHER WILL BE ONGOING THURSDAY NIGHT AS ANOTHER IN A
SERIES OF SHORTWAVES CONTINUES TO CROSS THE AREA WITH MORE SHOWERS
AND THUNDERSTORMS. BOTH THE NAM AND GFS ALSO KEEP PRECIPITATION
GOING INTO THE LATE NIGHT HOURS ACROSS EASTERN PORTIONS OF THE
COUNTY WARNING AREA SO WE KEPT POPS FAIRLY HIGH.

AS FOR FRIDAY IT LOOKS LIKE ANOTHER DAY OF SCATTERED SHOWERS AND
THUNDERSTORMS. AT THIS POINT...IT APPEARS A DAY WITH MORE CLOUDS AND
THE MODELS ARE SHOWING LESS INSTABILITY THAN ON PREVIOUS DAYS SO THE
INTENSITY OF THE STORMS MAY BE DIALED BACK A NOTCH OR TWO. WITH
INCREASED CLOUD COVER...TEMPERATURES WILL ALSO BE TRIMMED A COUPLE
OF DEGREES.

NOW...AT THIS POINT WITH THE CONTINUOUS SHOWERS OVER THE PAST
SEVERAL DAYS PEOPLE ARE LOOKING FOR A BREAK. IT IS TO THE POINT
WHERE PEOPLE...WEATHER GEEKS AT LEAST...ARE SCREAMING...A RIDGE...A
RIDGE...MY KINGDOM FOR A RIDGE. WELL...IT FINALLY LOOKS LIKE ONE
WILL BUILD ACROSS THE AREA. HOWEVER...IT DOES LOOK LIKE A FAIRLY
FLAT RIDGE SO IT WILL NOT SHUT OFF THE CONVECTION COMPLETELY.
AT THIS POINT FOR SATURDAY IT WILL BE THE FIRST TIME IN A WHILE
THAT A VAST MAJORITY OF THE AREA...ESPECIALLY THE LOWER
ELEVATIONS...WILL HAVE A DRY DAY. THERE WILL BE A WEAK SHORTWAVE
MOVING BY TO THE NORTH SO THERE WILL STILL BE A FEW THUNDERSTORMS
IN THE FAR NORTH. A THUNDERSTORM MAY ALSO FIRE OVER THE MOUNTAINS
WITH THE HIGH ELEVATION HEAT SOURCE. REGARDLESS...SATURDAY LOOKS
TO BE THE DRIEST DAY IN QUITE A WHILE. IN ADDITION...WITH MORE
SUNSHINE AND A LOW TURNING SOUTHWESTERLY...TEMPERATURES WILL
BEGIN A WARMING TREND...FEELING MORE LIKE WHAT YOU WOULD EXPECT
FOR THE LATTER PART OF MAY. A BIT MORE MOISTURE WILL THEN TRY TO
SNEAK INTO WESTERN WYOMING FOR SUNDAY...THE EUROPEAN AT THIS POINT
IS MORE BULLISH THAN THE GFS. AT THIS POINT...CONTINUITY LOOKED
REASONABLE SO WE MADE FEW CHANGES. TEMPERATURES WILL ALSO CONTINUE
TO WARM WITH MANY PLACES POSSIBLY SEEING 80 DEGREES FOR THE FIRST
TIME THIS YEAR. WE DID KEEP THINGS COOLER THAN MOS FOR NOW SINCE
AMPLE GROUND MOISTURE MAY LIMIT HEATING SOMEWHAT THOUGH.

HOWEVER...AS IS THE RULE THIS SPRING...IT WILL BECOME MORE ACTIVE
ONCE AGAIN AS A TROUGH DIGS INTO THE PACIFIC NORTHWEST AND A SERIES
OF SHORTWAVES CROSSES THE AREA FOR THE FIRST FEW DAYS OF THE WEEK.
THE MODELS ARE FAIRLY CONSISTENT WITH HAVING THE CHANCE OF
CONVECTION EACH DAY. HOWEVER...THE DETAILS OF COVERAGE AND PLACEMENT
VARY WIDELY...AS ONE WOULD EXPECT THIS FAR OUT. THE EUROPEAN IS
FURTHER SOUTH WITH COVERAGE ACROSS MOST OF THE AREA...WHILE THE GFS
KEEPS MOST OF THE ENERGY FURTHER NORTH. AGAIN...CONTINUITY LOOKED
DECENT SO WE MADE ONLY MINOR TWEAKS. AT THIS POINT MONDAY LOOKS TO
BE THE WARMEST DAY WITH THE GFS MOS HAVING HIGH TEMPERATURES
APPROACHING 90 IN SOME LOCATIONS. AGAIN...WE KEPT TEMPERATURES A BIT
COOLER BUT DID RAISE THEM A COUPLE. BUT STILL IT WILL DEFINITELY
FEEL LIKE JUNE. WITH MORE CLOUD COVER TOWARD MIDWEEK TEMPERATURES
SHOULD TREND DOWN A BIT TOWARD WEDNESDAY.

&&

.AVIATION.../06Z ISSUANCE/

SOME LINGERING SHOWERS FROM DISSIPATING EVENING THUNDERSTORMS WILL
LINGER ACROSS MAINLY ALONG THE INTERSTATE 80 CORRIDOR AND VCNTY AND
WEST OF THE DIVIDE OVERNIGHT.

AN UPPER LEVEL LOW PRESSURE SYSTEM WILL DRIFT EAST ACROSS WYOMING ON
THURSDAY BRINGING SCATTERED SHOWERS AND AFTERNOON THUNDERSTORMS
ACROSS THE AREA WITH THUNDERSTORMS EXPECTED TO BE MOST NMRS VCNTY
AND EAST OF INTERSTATE 25.  A COLD FRONT AND LOW LEVEL NORTHERLY
FLOW WILL FOLLOW THURSDAY NIGHT...WITH AREAS OF MVFR CIGS AND -RA
SPREADING SOUTH EAST OF THE CONTINENTAL DIVIDE OVERNIGHT.

&&

.FIRE WEATHER...

SHOWERS AND THUNDERSTORMS ARE POSSIBLE EACH AFTERNOON AND EVENING
WITH A GOOD CHANCE OF WETTING RAIN EACH DAY THROUGH FRIDAY. THERE WILL
BE A CHANCE FOR DRIER AND WARMER WEATHER THIS WEEKEND BUT THERE
IS ANOTHER STORMY PERIOD EXPECTED BY MONDAY NEXT WEEK. SMOKE DISPERSAL
EACH DAY WILL BE GOOD TO EXCELLENT...EXCEPT FOR SHORT PERIODS IN
THE VERY EARLY MORNING HOURS.

&&

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

$$

SHORT TERM...LAVOIE
LONG TERM...HATTINGS
AVIATION...AEM
FIRE WEATHER...LAVOIE








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