Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 210925
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
325 AM MDT TUE APR 21 2015

.SHORT TERM...MONDAY THROUGH WEDNESDAY NIGHT

ALL IS QUIET ON THE WEATHER FRONT THIS MORNING IN HUMBLE COUNTY
WARNING AREA OF WESTERN AND CENTRAL WYOMING TODAY. THINGS WILL GET A
BIT ACTIVE THIS AFTERNOON HOWEVER AS A WEAK SHORTWAVE MOVES THROUGH
THE FLOW AND TOUCHES OFF SOME ISOLATED TO SCATTERED THUNDERSTORMS
ACROSS AREAS WEST OF THE DIVIDE AND IN THE HIGHER ELEVATIONS.
HOWEVER...MOST AREAS SHOULD STAY DRY. IN ADDITION...STEERING FLOW IS
VERY WEAK SO THE CHANCES THE STORMS WOULD MOVE MUCH OFF OF THE
MOUNTAINS IS RELATIVELY SLIM. THESE SHOWERS SHOULD END WITH THE LOSS
OF DAYTIME HEATING WITH THE OVERNIGHT PERIOD QUIET ONCE AGAIN.
TEMPERATURES SHOULD ALSO WARM TODAY WITH MOST AREAS SEEING ABOVE
NORMAL READINGS...BUT NOT TOO OUT OF THE ORDINARY FOR THE LATTER
PORTION OF APRIL.

THE QUIET WEATHER SHOULD LAST INTO WEDNESDAY MORNING AS WELL. AS WE
HEAD INTO THE AFTERNOON THOUGH...EXPECT ANOTHER ROUND OF SHOWERS AND
THUNDERSTORMS ACROSS SIMILAR LOCATIONS AS SOME MOISTURE...ALTHOUGH
NOT A TON...GETS SHOVED NORTHWARD AHEAD OF ANOTHER CLOSED UPPER
LEVEL LOW THAT WILL BE MAKING ITS WAY INTO CALIFORNIA. THIS SHOULD
LEAD TO SOMEWHAT GREATER COVERAGE IN THUNDERSTORMS. HOWEVER...MUCH
LIKE TODAY...STEERING FLOW IS VERY LIGHT SO A LOT OF THE STORMS WILL
ONCE AGAIN HAVE TROUBLE MOVING OFF OF THE MOUNTAINS SO MANY LOWER
ELEVATIONS...ESPECIALLY EAST OF THE DIVIDE SHOULD REMAIN RAIN FREE.
EXPECT HIGH TEMPERATURES TO REMAIN FAIRLY SIMILAR TO TUESDAYS...JUST
A BIT ABOVE NORMAL. BY THURSDAY THE MOISTURE MAY BECOME A BIT DEEPER
STILL. AN ADDITION...A TROUGH MOVING IN FROM THE WEST MAY PROVIDE A
BIT MORE INSTABILITY TO BRING A BIT MORE COVERAGE IN CONVECTION.
AGAIN...NOT EVERYONE WILL SEE A STORM BUT WITH A BIT MORE STEERING
FLOW THERE WILL BE A CHANCE FOR SOME STORMS TO REACH THE LOWER
ELEVATIONS IN THE AFTERNOON AND EVENING.

.LONG TERM...FRIDAY THROUGH TUESDAY

SYNOPSIS...UNSETTLED CONDITIONS REMAIN OVER THE AREA FRIDAY AND
SATURDAY IN SPLIT FLOW WITH SCATTERED SHOWERS AND ISOLATED
AFTERNOON THUNDERSTORMS. A RIDGE OF HIGH PRESSURE WILL BUILD IN
SUNDAY AND MONDAY WITH CHANCES OF SHOWERS MAINLY CONFINED TO THE
MOUNTAINS.

DISCUSSION...GFS AND ECMWF IN GOOD OVERALL AGREEMENT ACROSS NORTHERN
AND CENTRAL ROCKIES THROUGH THE WEEKEND...AND THEN SHOW INCREASING
SPREAD THROUGH EARLY NEXT WEEK.

FRIDAY AND SATURDAY...SW LOW EJECTS OUT OF THE FOUR CORNERS REGION
INTO THE CENTRAL HIGH PLAINS ON FRIDAY AS KICKER SYSTEM DIVES OUT OF
THE GULF OF ALASKA INTO THE NW U.S.  BEST INSTABILITY...THOUGH
SLIGHT...IS FORECAST ACROSS SOUTHERN AND EASTERN WYOMING WITH
INVERTED SFC TROUGH EXPECTED TO RUN SE-NW ROUGHLY ALONG INTERSTATE
25.  ON SATURDAY...KICKER TROUGH IS EXPECTED TO SHEAR ACROSS THE
NORTHERN ROCKIES WITH THE GFS AROUND 12 HOURS FASTER THAN ECMWF
PUSHING THIS SYSTEM ACROSS THE AREA.  HOWEVER...MODELS ARE SIMILAR
WITH TIMING OF A SFC FRONT PUSHING SOUTH INTO NORTHERN WYOMING
SATURDAY AFTERNOON AND ACROSS CENTRAL/SOUTH SATURDAY EVENING.
EASTERN PORTIONS OF NATRONA AND JOHNSON COUNTY MAY SEE A FEW
STRONGER STORMS IN THE AFTERNOON WHERE THE SHEAR ENVIRONMENT LOOKS
MORE FAVORABLE AHEAD OF THE FRONT.

SUNDAY...UPPER TROUGH SHOULD BE MOSTLY EAST OF THE AREA BY SUNDAY
AFTERNOON WITH A DRIER MORE STABLE AIRMASS OVER THE CENTRAL AND
SOUTH...WHILE SOME MOISTURE IN W-NW FLOW KEEPS CHANCES OF SHOWERS
OVER THE WESTERN MTNS.

MONDAY AND TUESDAY....MUCH MORE UNCERTAINTY IN THE FORECAST FOR THIS
LATTER PERIOD.  GFS SWINGS NEXT PACIFIC TROUGH ONTO WEST COAST BY
00Z TUESDAY WHILE ECMWF STILL HAS THIS TROUGH WEST OF 140W WITH
UPPER RIDGE AMPLIFYING DOWNSTREAM ALONG THE WEST COAST.  EITHER
WAY...MONDAY LOOKS MAINLY DRY AND SEASONABLY MILD.


&&

.AVIATION.../12Z ISSUANCE/

EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES

SCATTERED SHOWERS AND ISOLATED STORMS WILL DEVELOP THIS AFTERNOON
OVER OR ALONG THE ABSAROKA AND WIND RIVER MOUNTAINS. A FEW SHOWERS
WILL ALSO OCCUR IN THE BIGHORN MOUNTAINS. ISOLATED SHOWERS MAY
OCCUR FROM NEAR A KCOD TO KLND LINE LATE THIS AFTERNOON INTO THE
EVENING HOURS. EXPECT OCCASIONAL MOUNTAIN OBSCURATION THIS AFTERNOON
INTO THE EVENING. MOST OF THE SHOWERS WILL DISSIPATE BY 06Z WED. VFR
CONDITIONS WILL PREVAIL AT THE TERMINAL SITES THROUGH THE PERIOD.
THERE MAY BE LOCAL MVFR CONDITIONS OVER AND NEAR THE MOUNTAINS.

WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES

SCATTERED SHOWERS WILL DEVELOP OVER THE WESTERN MOUNTAINS AFTER 19Z
WITH ISOLATED THUNDERSTORMS. THE ACTIVITY WILL DECREASE AFTER 03Z
WED. TERMINAL SITES MAY SEE SHOWERS AT TIMES FROM 21Z UNTIL 06Z WED.
EXPECT OCCASIONAL MOUNTAIN OBSCURATION THIS AFTERNOON INTO THE
EVENING. VFR CONDITIONS WILL PREVAIL AT THE TERMINAL SITES THROUGH
THE PERIOD. THERE MAY BE LOCAL MVFR CONDITIONS OVER AND NEAR THE
MOUNTAINS.
&&

.FIRE WEATHER...

TODAY LOOKS LIKE THE DRIEST AND MOST STABLE DAY OF THE WEEK WITH
ONLY ISOLATED AFTERNOON SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS.
OTHERWISE...THERE WILL BE A CHANCE FOR SHOWERS OFF AND
ON...ESPECIALLY AFTER WEDNESDAY BUT WITH A LOW CHANCE OF ANY WETTING
RAIN UNTIL LATE IN THE WEEK. OTHERWISE THERE ARE NO MAJOR WIND
EVENTS OR SIGNIFICANT LIGHTNING EPISODES ON THE HORIZON.
&&

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

$$

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







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