000
FXUS65 KRIW 152128
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
328 PM MDT WED MAY 15 2013

.SHORT TERM...TONIGHT THROUGH THURSDAY

WV ANALYSIS SHOWING SSW TROF OVER SWRN UT THIS AFTERNOON WITH
DEVELOPING DIFFUSE SFC LOW OUT IN FRONT NEAR SWRN WY. SMALL
DISTURBANCE EXITING NERN WY. MOISTURE FEED FROM HIGH PLAINS INTO
EASTERN PORTIONS OF WY...TRYING TO GET INTO EASTERN PORTIONS OF THE
CWA. HOWEVER...MOISTURE STILL QUITE LIMITED WITH MIXED OUT DPTS
RANGING MOSTLY FROM THE MID 20S TO MID 30S. BETTER BL MOISTURE IS
SPOTTY AND LOCATED OVER THE SWRN CWA NEAR THE SALT AND WYOMING
RANGES...AND AGAIN NEAR THE SRN BIG HORNS AND MEDICINE BOW MOUNTAINS
SE OF CASPER. CONVECTION IS PROCEEDING...OVER THE SOUTHERN CWA
STARTING AT THE UINTAH MOUNTAINS...FOLLOWED BY THE WIND RIVER AND
CONFLUENCE WITH THE ABSOROKAS. LATER THIS EVENING...ANOTHER IN A
SERIES OF WEAK IMPULSES WILL ENHANCE SHOWERS ACROSS THE WRN AND NWRN
CWA.

THURSDAY...SLOW UPPER LVL HEIGHT FALLS AS APPROACHING EPAC SW TROF
AMPLIFIES AS IT IMPINGES ON COAST AND BEGINS TO AFFECT WEAK RIDGING
ATOP OUR REGION. ONLY VERY SLIGHT TEMPERATURE DIFFERENCES
TOMORROW...WITH HIGHS PERHAPS A DEGREE OR TWO LESS THAN TODAY. SW
IMPULSE OVER WRN ID AND NV THIS AFTERNOON WILL AFFECT THE N CNTRL AND
NWRN CWA IN THE MORNING...WEST OF A KBPI TO KCOD LINE...BEFORE A
SLIGHTLY BROADER IMPULSE...JUST STARTING TO SHOW UP OVER WEST CNTRL
CA  SAT IMAGERY...WILL SWING AROUND AMPLIFYING TROF AND ARRIVE NEAR
OUR NWRN CWA LATE TOMORROW AFTERNOON AND EVENING...PROVIDING PERHAPS
ENOUGH EXTRA LIFT IN AND AROUND THE ELEVATED TERRAIN TO GET
MEASURABLE PRECIP WEST OF AN EVANSTON TO LANDER TO CODY LINE. MID
LVL MOISTURE WILL ALSO BE MORE AVAILABLE FOR PRECIP IN WRN AND NWRN
WY DURING THE DAY AND POPS... REFLECT THIS TREND.
ELSEWHERE...MEASURABLE PRECIPITATION WILL BE HARD TO COME BY WITH
ONLY VERY ISOLATED CHANCES AROUND THE REST OF THE CWA WITH A
SLIGHTLY BETTER CHANCE NEAR THE SRN BIG HORNS. APPROACH OF RATHER
WEAK JET ASSOCIATED WITH LEADING EDGE OF TROF WILL BE ENOUGH TO
ENHANCE UPWARD VERTICAL SHEAR THROUGH THE DAY AND INTO THE EVENING
WHICH MAY AID IN KEEPING SHOWER/THUNDER CHANCES GOING A BIT LATER
INTO THE EVENING.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY NIGHT

AS A PACIFIC LOW PRESSURE TROUGH MOVES INTO THE WEST COAST
AND DEEPENS...SOUTH SOUTHWEST FLOW ALOFT WILL INCREASE OVER
WESTERN AND CENTRAL WYOMING THURSDAY NIGHT.  PACIFIC MOISTURE
WILL BE LIMITED TO THE WEST WITH A DRY SLOT OVER SOUTHERN AND
CENTRAL WYOMING LIMITING CONVECTION TO THE WESTERN MOUNTAINS.
WARMING ILL ACCOMPANY THE SOUTH SOUTHWEST FLOW.  THE PACIFIC TROUGH
IS EXPECTED TO MOVE SLOWLY EAST AS IT MOVES INTO THE WESTERN GREAT
BASIN WITH THE SOUTH SOUTHWEST FLOW ALOFT INCREASING.  SHOWERS AND
ISOLATED THUNDERSTORMS WILL BE LIMITED TO THE WEST AND NORTH WITH A
DRY SLOT CONTINUING IN THE SOUTH AND CENTRAL AREAS.  TEMPERATURES
WILL CONTINUE TO WARM.  FRIDAY NIGHT THE PACIFIC TROUGH WILL BE OVER
IDAHO AND UTAH WITH MOISTURE AND CONVECTION SPREADING EAST IN THE
STRONG SOUTH SOUTHWEST FLOW ALOFT BRINGING ISOLATED SHOWERS EASY
WITH SCATTERED SHOWERS IN THE WEST...ALONG WITH ISOLATED EVENING
THUNDERSTORMS.  TEMPERATURES WILL CONTINUE THE WARMING TREND IN THE
EAST WITH COOLING IN THE WEST.  SATURDAY THE PACIFIC TROUGH WILL
BEGIN TO MOVE ACROSS WESTERN WYOMING WITH SHOWERS AND ISOLATED
AFTERNOON THUNDERSTORMS CONTINUING TO SPREAD EAST WITH AN INCREASE
IN COVERAGE OVER THE WEST AND NORTH.  TEMPERATURES WILL COOL WITH
CLOUD COVER AND INCREASED PRECIPITATION.  A SURFACE FRONT WILL MOVE
INTO THE NORTH THROUGH SATURDAY ADDING TO THE COOLING IN THE NORTH.
SATURDAY NIGHT THE FIRST PACIFIC TROUGH WILL MOVE EAST INTO THE
NORTHERN AND CENTRAL PLAINS WHILE A SECOND PACIFIC TROUGH DEVELOPS
OVER THE NORTHERN ROCKIES AND NORTHERN GREAT BASIN.  THIS WILL
CONTINUE TO BRING PACIFIC MOISTURE AND COLDER TEMPERATURES WITH
SCATTERED SHOWERS...MOST NUMEROUS IN THE WESTERN AND NORTHERN
MOUNTAINS...AND ISOLATED AFTERNOON THUNDERSTORMS SUNDAY.  THIS
SECOND TROUGH WILL BRING THE COLD FRONT THROUGH THE STATE FROM THE
NORTH WITH A SECONDARY COLD PUSH BEHIND THE INITIAL COLD FRONT
SUNDAY NIGHT. THE SECOND PACIFIC TROUGH WILL MOVE SLOWLY ACROSS
WESTERN AND CENTRAL WYOMING KEEPING THE THREAT OF SHOWERS ELEVATED
OVER THE AREA AND CONTINUE THE COOLING TREND THROUGH MONDAY AND
MONDAY NIGHT WITH A GRADUAL DECREASE IN SHOWERS THROUGH THE NIGHT. A
HIGH PRESSURE RIDGE WILL BUILD IN AS THE SECOND TROUGH MOVES EAST OF
THE AREA INTO THE NORTHERN AND CENTRAL PLAINS. THE HIGH PRESSURE
WILL BRING AND END TO THE SHOWERS AND BRING SOME WARMING WITH MORE
SUNSHINE ON TUESDAY. TUESDAY NIGHT WILL REMAIN ON THE COOL SIDE WITH
CLEARING AND GREATER RADIATIONAL COOLING.


&&

.AVIATION.../00Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL TONIGHT AT KCOD AND KWRL...WITH SHOWERS
AND A FEW THUNDERSTORMS PERSISTING THROUGH 04Z MOST OTHER TERMINALS
EXCEPT FOR KJAC WHICH MAY REMAIN UNSETTLED THROUGH 09Z. STORM MOTION
WILL BE LARGELY FROM WSW TO ENE. LOCAL MVFR CONDITIONS MAY OCCUR IN
VCNTY STORMS.  CLOUD BASES WILL LARGELY BE ABOVE 5K FT AGL WITH
SHOWERS AND STORMS ON THE DRY SIDE AND OUTFLOW DOMINATED WITH WIND
GUSTS NEAR SOME STORMS AT 30 TO 35 KTS. MOST TERMINAL SITES WILL
HAVE VCTS IN THEM BETWEEN TIL 02-03Z...EXCEPT KWRL. LINGERING SHOWERS
ARE EXPECTED THROUGH 06-09Z...AND THEN AGAIN AT KJAC AFTER 15Z
TOMORROW. MORE SHOWERS AND SOME THUNDER CAN BE EXPECTED THURSDAY
NEAR MOST TERMINALS...BUT AFFECTING WESTERN TERMINALS THE MOST. THE
LONE EXCEPTION WILL BE KWRL...WHERE SHRA OR TSRA SHOULD STAY OUT OF
THEIR REGIONAL FORECAST AREA. ROCK SPRINGS WILL ALSO FIND IN A BIT
HARDER THAN OTHERS TO GET THUNDER OR PRECIPITATION.


&&

.FIRE WEATHER...

SOMEWHAT COOLER TEMPERATURES TODAY...DOWN 5 TO 7 DEG...UPPER LEVEL
HEIGHT FALLS BEGIN A SLOW PROGRESSION INTO THE FORECAST AREA FROM
THE SOUTHWEST.  AHEAD OF THE AMPLIFYING TROF OUT WEST...SEVERAL
UPPER LEVEL DISTURBANCES WILL CONTINUE TO IMPACT THE STATE OVER THE
NEXT SEVERAL DAYS. CURRENTLY CONVECTION IS PROCEEDING...STARTING
OVER THE UINTAH MOUNTAINS AND MOVING INTO THE SOUTHERN PORTIONS OF
WY. THIS WAS FOLLOWED BY THE WIND RIVER REGION AND AND CONFLUENCE
WITH THE ABSOROKAS. THIS EVENING...ANOTHER IN A SERIES OF WEAK
IMPULSES WILL ENHANCE SHOWERS ACROSS THE WRN AND NWRN TERMINALS
INCLUDING KJAC. TEMPERATURES WILL CONTINUE TO COOL THROUGH THURSDAY
WITH A SLIGHT REBOUND ANTICIPATED FRIDAY AFTERNOON AHEAD OF THE
STRONGER WAVE OF LOW PRESSURE DUE TO ARRIVE THIS WEEKEND.


&&

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

$$

SHORT TERM...BRAUN
LONG TERM...C.BAKER
AVIATION...BRAUN
FIRE WEATHER...BRAUN