National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS65 KRIW 150525
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1125 PM MDT TUE MAY 14 2013

.SHORT TERM...TONIGHT THROUGH WEDNESDAY (ISSUED AT 335 PM MDT)

UPPER LEVEL FLAT RIDGING TODAY WITH SLIGHTLY LOWER HEIGHTS THAN THE
PREVIOUS DAY...AND CONTINUED SLOW HEIGHT FALLS THROUGH
TOMORROW...RESULTING IN SLIGHTLY COOLER TEMPS. VERY DRY RIW SOUNDING
THIS MORNING WITH ONLY MOISTURE SHOWING UP IN NARROW BAND BETWEEN H6
AND H5. NEARER THE SURFACE...FRONT IN CENTRAL WYOMING THIS MORNING
HAS NOW PUSHED TO THE SOUTHEASTERN CORNER OF WY AND NORTHEASTERN CO
WITH INVERTED TROF EXTENDING TOWARDS NORTHWESTERN WY. SLIGHTLY
BETTER MOISTURE AND LOW LEVEL FORCING WILL ALLOW FOR VERY ISOLATED
CHANCES FOR TS IN SOUTHEASTERN AND SOUTH CENTRAL WY...PERHAPS
GETTING INTO CARBON OR SWEETWATER COUNTY BY EARLY EVENING. ALTHOUGH UPPER
LEVEL DYNAMICS IS BETTER OVER THE NORTHERN HALF OF THE
STATE...GENERALLY DRY BOUNDARY LAYER ATMOSPHERE AND INCREASING
STABILITY TODAY WILL KEEP SKIES FROM CRYING ACROSS MOST OF THE
REGION.

TOMORROW...SHORTWAVE TROF THAT IS CURRENTLY LOCATED OVER CENTRAL
CALIFORNIA WILL DEVELOP CYCLONE OVER CENTRAL NEVADA AND WESTERN UTAH
THIS EVENING AND PUSH INTO SOUTHWESTERN WY BY 12Z WEDNESDAY...WITH A
WEAK TROF EXTENDING INTO NORTHEASTERN WY. THIS WILL EFFECTIVELY HALT
THE PROGRESSION OF THIS EVENING`S DRY FRONT GENERALLY...THERE WILL
BE ISOLATED THUNDERSTORMS POSSIBLE ACROSS THE ENTIRE CWA
WEDNESDAY...WITH SCATTERED CHANCES MOSTLY OVER NATRONA AND
JOHNSON COUNTIES DUE TO INCREASED AVAILABLE MOISTURE AS LOW
CONTINUES TO DEVELOP AND DRAGS WATER INTO THE STATE FROM THE
SOUTHEAST. ELEVATED TERRAIN WILL BE FAVORED ACROSS THE CWA. CI WILL
LIKELY OCCUR NEAR AND ALONG THE GREEN MOUNTAINS TO THE MEDICINE
BOWS...FROM NORTHEAST OF ROCK SPRINGS TO SOUTH OF CASPER BY MIDDAY.
LOW TO ML CAPE VALUES SHOULD TOP OUT AROUND 500 J/KG ACROSS THE ERN
CWA...DECREASING WWD. RELATIVELY LOW SHEAR VALUES WILL LIMIT BOTH
STORM STRENGTH AND LONGEVITY...TENDING TOWARDS PULSE TYPE
THUNDER.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY NIGHT

WE LOOK TO BE ENTERING A MORE ACTIVE PERIOD THROUGH MUCH OF THE LONG
RANGE AS A LONG WAVE TROUGH DEVELOPS ACROSS MUCH OF THE WESTERN
UNITED STATES. A WEAK AREA OF LOW PRESSURE MAY SPIN UP EAST OF THE
BIG HORN RANGE AND MAY KEEP SHOWERS GOING INTO WEDNESDAY NIGHT. BY
THURSDAY MOST OF THE QPF PUSHES JUST EAST OF THE COUNTY WARNING AREA
INTO THE BLACK HILLS SO MOST AREAS THERE HAVE ONLY ISOLATED POPS FOR
AFTERNOON AND EVENING THUNDERSTORMS WITH THE EXCEPTION OF THE BIG
HORN RANGE. THE MOST ACTIVE REGION LOOKS TO BE AREAS WEST OF THE
DIVIDE WHERE ANOTHER SHORTWAVE MOVING INTO THE AREA WILL BRING A
BETTER CHANCE OF SHOWERS AND THUNDERSTORMS. HOWEVER...THIS DOES NOT
LOOK LIKE AN ALL DAY RAIN FOR MOST AREAS AND MUCH OF THE TIME WILL
BE RAIN FREE...ESPECIALLY EAST OF THE DIVIDE. BY FRIDAY THE MODELS
HAVE COME SOMEWHAT BETTER AGREEMENT IN FOCUSING THE BULK OF
PRECIPITATION ACROSS WESTERN AND NORTHERN WYOMING WITH AND DRIER
CONDITIONS IN SOUTHERN AND EASTERN AREAS AS A COLD FRONT MOVES
ACROSS THE REGION. TEMPERATURES LOOK TO STAY ABOVE NORMAL THROUGH
THE PERIOD WITH WARM SOUTHWESTERLY FLOW CONTINUING AHEAD OF THE
FRONT.

THE WEATHER THEN TURNS COOLER AND MORE UNSETTLED FOR THE WEEKEND AS
THE POSITION OF THE LONG WAVE TROUGH SHIFTS OVER WYOMING. WITH THE
TROUGH ONLY MOVING SLOWLY TO THE EAST EXPECT A DAILY CHANCE OF
SHOWERS AND THUNDERSTORMS EACH DAY. MODELS ARE STILL A BIT MUDDY ON
THE TIMING OF SHORTWAVES AND WHICH DAY WOULD BE THE WETTEST SO WE
MADE EACH DAY BASICALLY THE SAME WITH THE HIGHEST POPS ACROSS
NORTHERN AND WESTERN WYOMING. PRECIPITATION ALSO LINGERS INTO MONDAY
AS WELL. BY TUESDAY...BOTH THE EUROPEAN AND GFS SHOW A RIDGE
BUILDING ACROSS THE STATE BRINGING MAINLY DRY AND SOMEWHAT WARMER
WEATHER.


&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL CONTINUE 21Z WEDNESDAY. EXPECT ISOLATED
THUNDERSTORMS FOR MOST OF THE TERMINALS ON WEDNESDAY EXCEPT IN THE
NORTH WHERE ACTIVITY WILL BE LESS THAN IN THE CENTRAL AND SOUTH.
LOCAL MVFR CONDITIONS MAY OCCUR IN STORMS FROM 21Z UNTIL 02Z.
ISOLATED SHOWERS WILL LINGER UNTIL 06Z ACROSS THE CENTRAL AND SOUTH.

&&

.FIRE WEATHER...

BEHIND ONE COOL DRY FRONT AND AHEAD OF ANOTHER DESTINED TO ARRIVE
ACROSS NORTHERN WY THIS EVENING. NO THUNDERSTORMS FOR THE MOST PART
THE REST OF TODAY AS ATMOSPHERE IS TOO DRY AND STABLE...EXCEPT FOR A
VERY SMALL CHANCE OF A STORM OR TWO SNEAKING INTO THE EXTREME
SOUTHERN PORTIONS OF EITHER SWEETWATER OR CARBON COUNTIES.
TEMPERATURES ARE RUNNING SOME 3 TO 6 DEGREES COOLER ACROSS MOST OF
THE FORECAST AREA TODAY AND WILL DECREASE ANOTHER 4 TO 6 DEGREES
TOMORROW. TODAY THE MAIN CONCERN WILL REMAIN WITH GUSTY WEST TO
SOUTHWEST WINDS OVER THE WESTERN TWO THIRDS OF THE FORECAST AREA AND
NORTH TO NORTHWEST WINDS ACROSS THE EASTERN THIRD. TOMORROW WILL
HOLD MUCH BETTER INSTABILITY FOR THUNDERSTORM FORMATION...HOWEVER
EVEN THEN STORMS WILL BE ISOLATED EXCEPT FOR PORTIONS OF MEDICINE
BOW AND BIG HORN MOUNTAINS WHERE MOISTURE WILL BE MORE AVAILABLE AND
SCATTERED THUNDER WILL BE A POSSIBILITY. IN GENERAL...WINDS SHOULD NOT BE AS
STRONG AND GUSTY TOMORROW EXCEPT NEAR THUNDERSTORMS.


&&

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

$$

SHORT TERM...BRAUN
LONG TERM...HATTINGS
AVIATION...AR
FIRE WEATHER...BRAUN