Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 151000
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
400 AM MDT FRI AUG 15 2014

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT

WV IMAGERY SHOWING SW TROF MOVING THRU WY TO THE ENE...KEEPING
THINGS JUST UNSTABLE ENOUGH FOR A FEW SHOWERS AND ISOLATED STORMS TO
CONTINUE OVERNIGHT FROM CNTRL THRU THE ERN FA. OTHERWISE...LG CLOSED
LOW OVR PAC NW WITH EMBEDDED SW JUST NOW SWINGING THRU THE SW CORNER
OF OR...UNDERCUTTING THE LOW AND WILL EVENTUALLY HEAD THIS DIRECTION
ARRIVE NEAR THE WRN FA BY TOMORROW AFTERNOON. SOME MID/UPR DRYING
ALREADY MOVING INTO THE WEST WITH MAIN UPR HI CENTERED FAR SOUTH OVR
THE DESERT SW. MONSOONAL MOISTURE APPEARS TO BE ON THE WAY OUT OF
THE FA AS THE UPR HI CONTINUES TO MIGRATE WWD AND DRY AIR MOVES IN
FROM THE SW. . AT THE SFC...NOT MUCH GOING ON ATTM WITH GENERAL
DIFFUSE HI P ACROSS THE ROCKY MOUNTAIN STATES AND A WEAKENING SFC
LOW OVR THE SW CONUS.

OVERALL...DRYING TREND BEGINS TODAY AND CONTINUES VIGOROUSLY THRU
THE FCST PERIOD...WITH INCREASES IN FIRE DANGER. FOR ALL INTENSIVE
PURPOSES TODAY WILL BE THE LAST DAY FOR ANY REAL CHC FOR PRECIP
ANYWHERE IN THE CWA...EVEN THEN THOSE CHANCES WILL OCCUR MAINLY
ACROSS THE WRN TO NRN MOUNTAINS WHERE RESIDUAL MOISTURE...MID LVL
MOISTURE AND FORCING ALONG THE LEADING EDGE OF THE SW KICKING THIS
WAY FROM OR (MENTIONED ABOVE)...AND TERRAIN FORCING COME TOGETHER IN
THE AFTERNOON. AT THE SAME TIME THE CWA WILL BE DRYING OUT FROM A
SYNOPTIC STANDPOINT...AS UPR FLOW BECOMES SW TO W ORIENTED AS WILL
THE SFC WIND WITH LOW P MOVING E AND HI P FILLING IN WEST. LOSING
SOME 2 TO 3 TENTHS IN PW OVR THE HIGH MOISTURE OF THE LAST FEW DAYS.
ADDITIONALLY...STORM MOVEMENT/SPEED WILL BE EAST TO NORTHEAST AND
MUCH FASTER AS THE MID AND UPR LVL FLOW INCREASES IN RESPONSE TO THE
APPROACH OF THE NW PAC LOW. SO LESS ACTIVITY AND LESS RAINFALL WHERE
IT DOES OCCUR FOR ALL THESE REASONS.

BY SAT...THE FA CONTINUES TO DRY OUT AND WINDS BECOME QUITE
UNIDIRECTIONAL VERTICALLY...BRINGING DOWN STRONGER GUSTY WINDS FROM
ABOVE BY AFTERNOON. WILL HAVE TO WATCH THIS PERIOD AS IT IS
BEGINNING TO LOOK LIKE AT LEAST A BORDERLINE RED FAG DAY ACROSS
SWEETWATER COUNTY AND POSSIBLY PORTIONS OF SRN LINCOLN COUNTY. WILL
SEE WHAT IT LOOKS LIKE TO THE DAY CREW FOR POSSIBLE WATCH/WARNING
CONDITIONS. OTHERWISE...NOT MUCH CHC FOR PRECIP W/ ONLY THE SMALLEST
POSSIBILITY ACROSS THE FAR NRN MOUNTAINS. BASICALLY THE SAME THING
SUNDAY...MAINLY NO RAIN CHCS AGAIN BUT LESS WIND FOR MOST PLACES
THAN ON SAT...EXCEPT FOR MAYBE NATRONA COUNTY.

.LONG TERM...MONDAY THROUGH FRIDAY

MONDAY LOOKS MOSTLY DRY WITH ISOLATED MOUNTAIN AND ADJACENT
FOOTHILLS SHOWERS OR STORMS IN THE AFTERNOON AND EVENING. ON TUESDAY
THE ECMWF MODEL SHOWS A WEATHER SYSTEM MOVING THROUGH THE REGION IN
A SW FLOW ALOFT. THE GFS MODEL IS HINTING AT SOMETHING AS WELL BUT
APPEARS WEAKER. WILL KEEP ISOLATED SHOWERS AND STORMS IN THE
FORECAST FOR MOST MOUNTAINS AND FOOTHILLS WITH VERY ISOLATED
ACTIVITY LOWER ELEVATIONS. THE ECMWF SHOWS A WEATHER SYSTEM MOVING
THROUGH ON WED WHILE THE GFS IS MUCH WEAKER AGAIN. WILL KEEP THE
ISOLATED SHOWERS AND STORMS FOR THE MOUNTAINS AND NEARBY FOOTHILLS
AS WELL AS OVER THE FAR NORTH. BREEZY AREAS AS WELL ON WED PM AND
EVENING. THE WEATHER PATTERN GETS MORE COMPLICATED THURS AND FRI
DEPENDING ON WHICH MODEL YOU LOOK AT. THE ECMWF MODEL AND THE GEM
MODEL ARE MORE ALIKE. THEY BRING A WEATHER SYSTEM INTO IDAHO AND
MONTANA THURSDAY WITH A COLD FRONT INTO NORTHERN WY BY 00Z FRI. THIS
WOULD LEAD TO A CHANCE OF SHOWERS/STORMS OVER THE NORTH THURSDAY PM
AND NIGHT. DRY CENTRAL AND SOUTH. THEN ON FRIDAY ANOTHER DISTURBANCE
PUSHES THROUGH WITH COOLER AIR AND A SLIGHT CHANCE OF STORMS FOR THE
NORTH AND CENTRAL WITH THE SOUTH STAYING DRY. THE GFS MODEL DIGS A
WEATHER SYSTEM INTO THE PACIFIC NW THURSDAY AND THEN FORMS A LARGE
TROUGH OVER THE WEST FRIDAY AS IT INGESTS AND UPPER SYSTEM FROM OFF
THE CALIFORNIA. THIS SOLUTION SEEMS A BIT MUCH TO BELIEVE THAT FAR
OUT AND WILL NOT FOLLOW THIS FOR NOW...UNLESS THE ECMWF CHANGES ITS
MIND. AS FOR TEMPS...A TAD COOLER CENTRAL AND EAST MONDAY THEN
SUMMER HEAT FOR TUESDAY THROUGH THURSDAY AND THEN COOLER FRIDAY.

&&

.AVIATION.../12Z ISSUANCE/

ANY LINGERING ISOLATED -SHRA EARLY THIS MORNING SHOULD BE GONE BY
12Z. PATCHY FOG/LOW CLOUDS ARE POSSIBLE THROUGH ABOUT 15Z...MAINLY
OVER THE WESTERN VALLEYS/BASINS ESPECIALLY IN AREAS THAT RECEIVED
RAINFALL. OTHERWISE SKC TO SCT100 AND LIGHT WINDS ARE EXPECTED THIS
MORNING. ALTHOUGH DRIER AIR WILL WORK INTO THE MID LEVELS...ISOLATED
TO LOCALLY SCATTERED CONVECTION IS EXPECTED ALONG AND NORTHWEST OF A
KAFO-KPNA-KCOD LINE...WITH ISOLATED MAINLY MOUNTAIN CONVECTION
EXPECTED ELSEWHERE. CONVECTION WILL QUICKLY DISSIPATE BETWEEN 02Z
AND 04Z...WITH MAINLY SKC CONDITIONS BY 06Z SATURDAY.

&&

.FIRE WEATHER...

FIRE WEATHER CONCERNS WILL BEGIN TO INCREASE SATURDAY AND SUNDAY AS
THE REGION BEGINS TO GET CUT OFF FROM THE MONSOON MOISTURE AND DRY
WEST TO SOUTHWEST FLOW FILLS IN ACROSS THE REGION.  TODAY...A
RELATIVELY WEAK UPPER LEVEL DISTURBANCE WILL MOVE ACROSS THE WEST
AND NORTH...COMBINING WITH RESIDUAL MOISTURE AMD DIURNAL FORCING
FROM TERRAIN FEATURES TO GET ISOLATED TO WIDELY SCATTERED CHANCES
FOR THUNDERSTORMS...MAINLY ACROSS THE WESTERN AND NORTHERN
MOUNTAINS. MINIMUM RH VALUES WILL GENERALLY RUN FROM 20 TO 40
PERCENT FOR MOST LOCATIONS TODAY WITH WINDS AT OR BELOW 20 MPH
EVERYWHERE. THIS WEEKEND...DRY WESTERLIES REALLY TAKE HOLD WITH
LITTLE CHANCE FOR PRECIPITATION ANYWHERE AND LOW ELEVATION
TEMPERATURES RISING INTO THE UPPER 80S TO AROUND 90 WHILE MINIMUM RH
VALUES FALL INTO TH LOWER AND MIDDLE TEENS. WINDS ON SATURDAY WILL
ALSO PICK UP OUT OF THE WEST...WITH GUSTS RANGING TO NEAR CRITICAL
LEVELS...DEFINITELY ENHANCING FIRE DANGER...ESPECIALLY ON
SATURDAY.

&&

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

&&

$$

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



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