Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KRIW 022027
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
227 PM MDT WED SEP 2 2015

.SHORT TERM...TONIGHT THROUGH THURSDAY

WV IMAGERY SHOWING MODEST BROAD RIDGING PATTERN ACROSS MOST OF THE
CONUS AND WY UNDER SW FLOW...WHILE THE WCST AND PAC NW STATES ARE
THE ONLY AREA UNDER THE INFLUENCE OF A LARGE FALL-LIKE TROF. MINOR
EMBEDDED SW/JET STREAK ACROSS NERN NV/NRN UT...WITH A STRONGER
EMBEDDED WAVE OVR SRN AZ/SWRN NM. SFC HAS HIGH P TO THE S OVR THE 4
CORNERS AND LOW P TO THE N SPLITTING MT WITH A TROF SAGGING DOWN
INTO CNTRL/SWRN WY.

WARM/VERY DRY TODAY WITH TYPICAL S TO SWRLY SFC WINDS GUSTING 20 TO
30 MPH...ESPECIALLY ACROSS THE SRN/SERN FA...RAISING FIRE DANGER
CONCERNS OVR CRITICAL FUEL AREAS...MOST OF THE LOWER ELEVATIONS...
TO THE RED FLAG CATEGORY. THIS DRY AND WINDY STATE...WHILE
DECREASING OVERNIGHT...WILL GENERALLY HANG AROUND THROUGH AT LEAST
PART OF THE DAY THURSDAY...PARTICULARLY EAST OF THE DIVIDE...WITH
RFW SET TO EXPIRE THU EVENING. NOT MUCH IN THE WAY OF ANY
THUNDERSTORM ACTION IS EXPECTED TODAY WITH A DRY CAPPED ATMOSPHERE
IN PLACE AND LITTLE SFC TO MID LVL FORCING TO OVERCOME THE LID.
TONIGHT...HOWEVER...THE SMALL SW/JET STREAK COMING INTO NRN UT WILL
ARRIVE NEAR/OVR THE WRN FA NEAR MIDNIGHT...DEVELOPING A WEAK SFC
BOUNDARY/LOW...AND WEAKENING THE CAP JUST ENOUGH IN THAT AREA TO
ALLOW SOME SHRA/ISOLATED THUNDER ACTIVITY TO BLOSSOM FOR A SHORT
PERIOD BEFORE MOVING OUT BY THU AM.

THEN...AS THURSDAY PROGRESSES...THE NEXT STRONGER UPR WAVE...
CURRENTLY LOCATED OVR THE DESERT SW...WILL HEAD INTO SRN WY ALONG
WITH A SMALL BUT DECENT BLOB OF MONSOONAL MOISTURE. THIS WILL
GREATLY INCREASE MOISTURE AND CLOUD COVER ACROSS THE WEST AND
ESPECIALLY THE SRN AND SERN CWA INTO/THRU THE AFTERNOON
PERIOD...APPEARING TO LOWER THE FIRE DANGER POTENTIAL FOR THIS
AREA...ALTHOUGH WINDS MAY STILL OCCASIONALLY GUST OVER 20 MPH AT
TIMES. HARD TO SAY HOW THIS WILL PLAY OUT EXACTLY...BUT IT`S
BEGINNING TO LOOK LIKE RED FLAG CONDITIONS WEST OF THE DIVIDE MAY
NOT PLAY OUT TOMORROW. THE REGION MOST LIKELY TO SEE RED FLAG
CONDITIONS THURSDAY WILL BE ERN FREMONT...NERN SWEETWATER...AND
NATRONA/JOHNSON COUNTIES. WILL SEE WHAT THE NIGHT CREW THINKS ABOUT
TOMORROW`S FIRE WX CHANCES AS THE TRAJECTORY OF MOISTURE FROM THE
SOUTH BECOMES MORE CLEAR.

OTHERWISE...LOW P JUMPS FROM ERN ID AND DEVELOPS IN THE LEE OF THE
ABSAROKAS OVR THE BIG HORN BASIN...WITH HIGH PRESSURE AND MOISTURE
INFILTRATING SRN/SERN WY. A LINE FROM ROUGHLY FROM EVANSTON TO
KAYCEE AND POINTS EWD WILL BE THE AREA THAT WILL SEE THE BEST
CHANCES BY THE END OF THE FCST PERIOD FOR WIDELY SCATTERED/SCATTERED
PRECIP...WITH GUSTY WIND PRODUCERS EARLY BEING REPLACED BY BRIEF
HEAVY RAIN TYPE STORMS. NORTH OF THIS LINE...MORE ISOLATED SHRA/ISO
THUNDER WILL BE THE RULE...WITH LITTLE IF ANY PRECIP ACROSS THE WEST
IN THE AFTERNOON.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY.

THE SLOW MOVING TROUGH OVER THE PAC NW WILL CONTINUE PUMPING SOME
MID LEVEL MOISTURE FROM THE SOUTH-SOUTHWEST OVER WYOMING FROM THU
NIGHT INTO SATURDAY.  NEAR SURFACE WINDS WILL BE BREEZY TO WINDY
DURING THE AFTERNOONS AND EARLY EVENINGS...ALTHOUGH HUMIDITIES SEEM
TO BE SLOWLY INCREASING AS MOISTURE FROM THE CENTRAL ROCKIES GETS
DRAWN UP. FRIDAY AFTERNOON AND EVENING LOOK TO HAVE SLIGHT
INSTABILITY OVER THE WESTERN MOUNTAINS AND SOUTHERN BIGHORNS FOR A
SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS.  AS THE CORE OF THE
TROUGH MOVES INTO IDAHO ON SATURDAY...INSTABILITY SHOULD INCREASE IN
WESTERN WYOMING FOR SCATTERED SHOWERS AND THUNDERSTORMS IN THE
AFTERNOON.  THE MOVEMENT OF THE CLOSED LOW INCREASES AT THIS TIME
TRACKING FROM CENTRAL IDAHO ACROSS YNP AND INTO NE MONTANA BY SUNDAY
AFTERNOON.  AT THIS TIME...700MB TEMPS OF -3 TO -4C ARE LIKELY
ACROSS NW WYOMING FROM SUNDAY MIDNIGHT TO NOON...CHANGING THE
OROGRAPHIC RAIN OVER TO SNOW ACROSS THE TETONS AND YNP.  AT THIS
TIME...EXPECTING 1-2 INCHES IN THE LOWER ELEVATIONS OF YNP BY NOON
SUNDAY...WITH TETON...BEARTOOTH...AND TOGWOTEE PASSES GETTING IN ON
THE ACTION AS WELL. THE GREATEST CHANCE OF PRECIPITATION ACROSS
WESTERN AND CENTRAL WYOMING LOOKS TO BE FROM SATURDAY AFTERNOON INTO
SUNDAY MORNING.

WITH THE CLOSED LOW STAYING TO THE NORTH...SOUTHERN AND CENTRAL
WYOMING WILL BE IN THE WINDY SOUTHERN SECTOR AS TEMPERATURES DROP TO
THE MID TO UPPER 30S ACROSS SW WY...AND LOW 40S IN THE CENTRAL AND
NORTHERN BASINS.  AT THIS TIME ALL OF THE MODEL GUIDANCE IS IN
PRETTY GOOD AGREEMENT THROUGH SUNDAY.  CLEARING AND WARMING IS
EXPECTED MONDAY THROUGH WEDNESDAY...EXCEPT FOR THE GFS WHICH IS
BRINGING ANOTHER WEAKER TROUGH DOWN FROM ALBERTA INTO NW WY BY EARLY
TUESDAY MORNING. APART FROM THIS ANOMALY...MONDAY THROUGH WEDNESDAY
LOOKS TO BE MOSTLY CLEAR WITH STEADY AT OR BELOW NORMAL TEMPERATURES
THAT WILL MAKE ONE FEEL LIKE FALL IS STARTING IN THE NORTHERN
ROCKIES.


&&

.AVIATION.../00Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL FOR ALL TERMINALS THROUGH THE END OF THE
FORECAST PERIOD.

BREEZY TO WINDY CONDITIONS WILL OCCUR AT MANY TERMINAL SITES
THROUGH EARLY THIS EVENING...THEN AGAIN AFTER 19Z. FROM 03Z TO
12Z...ISOLATED SHOWERS OR POSSIBLY A THUNDERSTORM OR TWO ARE
POSSIBLE ACROSS FAR WEST AND NORTHWEST. OTHERWISE...LLWS WILL
BECOME AN INCREASING POSSIBILITY AROUND THE FORECAST AREA TONIGHT
AS LOW LEVEL INVERSIONS SETTLE IN BY/AFTER 06Z. AT THE MOMENT THE
TWO MOST LIKELY TERMINALS TO SEE THIS WIND SHEAR ARE KBPI AND
KCPR...BOTH ENDING BY 12Z. SHOWER/THUNDER CHANCES WILL INCREASE
FROM THE SOUTH AFTER 21Z...WITH VCSH/VCTS POSSIBLE NEAR
KRKS...KCPR...AND POSSIBLY KWRL IN THE AFTERNOON.

&&

.FIRE WEATHER...

FIRE DANGER EXTREME TODAY ACROSS MOST OF THE FORECAST AREA WITH
MINIMUM RH VALUES RANGING FROM THE 10 TO NEAR 15 PERCENT FOR MOST
LOW ELEVATIONS...AND WINDS WINDS GENERALLY OUT OF THE SOUTH TO
SOUTHWEST GUSTING TO BETWEEN 20 AND 30 MPH AT TIMES. TONIGHT...RH
AND WIND VALUES WILL DROP BELOW CRITICAL BEFORE RETURNING TO EXTREME
AGAIN THURSDAY...ESPECIALLY ACROSS PORTIONS OF THE CENTRAL BASINS.
MOISTURE AND PRECIPITATION CHANCES WILL BE ON THE INCREASE ACROSS
THE FORECAST AREA THURSDAY...WITH BEST AREAS FOR SHOWERS AND
ISOLATED THUNDER ACROSS SOUTHERN AND SOUTHEASTERN WYOMING AS AN AREA
OF MONSOONAL MOISTURE RETURNS TO THE REGION. EXTREME FIRE DANGER
CONDITIONS WILL END FROM SOUTH/SOUTHWEST TO THE NORTH THROUGH THE
DAY. IN GENERAL...MOISTURE WILL BE ON THE INCREASE ACROSS THE
FORECAST AREA THROUGH THE WEEKEND...HELPING TO KEEP FIRE DANGER IN
CHECK EVEN THOUGH WINDS WILL BE ON THE GUSTY SIDE AT TIMES.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THURSDAY FOR WYZ275>277-279>283-
285-287-289-300-414>416.

&&

$$

SHORT TERM...BRAUN
LONG TERM...MCDONALD
AVIATION...BRAUN
FIRE WEATHER...BRAUN


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.