Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Graphics & Text | 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 041937
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
137 PM MDT WED MAY 4 2016

.SHORT TERM AND LONG TERM...TONIGHT THROUGH NEXT WEDNESDAY

WARM RIDGE AXIS CENTERED OVER THE AREA WILL GRADUALLY SHIFT SLOWLY
EWD INTO THURSDAY AFTERNOON ALLOWING OUR UPPER LOW TO SLOWLY MOVE
TOWARD THE SOCAL COAST. THE MAJORITY OF THE GUIDANCE TAKE THIS
LARGE UPPER LOW INTO THE DESERT SW FRIDAY NIGHT INTO SATURDAY. AT
THE SAME TIME...A NRN PLAINS SHORTWAVE WILL PUSH A COOL FRONT SWD
QUICKLY DURING THE DAY FRIDAY. SETTING UP OUR CLASSIC PATTERN OF
UPSLOPE FOR AREAS ALONG AND EAST OF THE DIVIDE COMBINED WITH UPPER
DYNAMICS FROM THE LOW OVERRUNNING THIS COLD DOME. RAIN AMOUNTS
SHOULD BE SIGNIFICANT WITH RATHER HIGH SNOW LEVELS AT LEAST
INITIALLY...THEN GRADUALLY LOWERING LATER SATURDAY INTO SATURDAY
NIGHT. SNOW LEVELS WILL LIKELY START OUT FRIDAY EVENING NEAR 10K
FEET BUT WILL SLOWLY SLOWER INTO SATURDAY AFTERNOON. GFS IS COOLER
THAN THE NAM BY AT LEAST 500 TO 1000 FEET. WILL HAVE TO WATCH THIS
CLOSELY AS TO LOWER SNOW LEVELS WILL DEFINITELY HELP WITH THE
INITIAL AMOUNT OF RUNOFF OVER THE WEEKEND. THE MORE I LOOK AT
IT...THE MORE I LEAN TOWARDS THE LOWER SNOW LEVELS. SO INSTEAD OF
THE 9500 TO 10000 FEET SATURDAY MORNING THAT THE NAM12 WOULD GIVE
US...I`D LEAN TOWARDS THE 9000 FEET OR SO THAT THE GFS20 SHOWS.
SOMETHING TO WATCH. WHAT I DON`T LIKE IS THE MUCH DRIER GFS
THOUGH. STORM TOTALS ARE GENERALLY .75 TO 1 INCH ON THE GFS WHILE
THE 12Z ECMWF IS 4+ INCHES AROUND HERE AND AT LEAST 2-3 INCHES ON
THE GEM. LEAN TOWARDS A MIDDLE GROUND STILL WITH 1 TO 2 INCHES
ACROSS THE LOWER ELEVATIONS OF CENTRAL WYO WITH CLOSER TO 2 IN THE
WRN HALF OF THE WIND RIVER BASIN AND ABOVE 2 CLOSER TO THE
FOOTHILLS FROM AROUND LANDER NWWD ALONG THE FOOTHILLS WITH 2 TO 4
INCHES ALONG THE EAST SLOPE OF THE WINDS WITH 2-3 INCHES IN THE
SRN ABSAROKAS.

MODELS STILL STRUGGLING WITH WHERE THE LOW WILL END UP BY SUNDAY
MORNING AND HOW FAST IT WILL MOVE EAST OF THE AREA. GFS IS ONCE
AGAIN SHOWING A PIECE OF THE LOW LIFTING NWD INTO SRN WYO AND
STALLING OUT INTO MONDAY MORNING BEFORE JOINING THE REST OF THE LOW
OVER NEBRASKA LATER MONDAY. THE 12Z EURO LIFTS IT INTO FAR NRN
CO/EXTREME SRN WY SUNDAY MORNING AND THE SLOWLY MOVES IT OFF TO
WRN NE BY SUNDAY EVENING. A VERY WET SOLUTION FROM THE EURO WITH
OVER 4 INCHES ACROSS THE WIND RIVER BASIN VS THE INCH OR LESS ON
THE GFS. WILL STICK WITH MY INITIAL FEELING FROM THE PAST COUPLE
DAYS AS STATED IN THE FIRST PARAGRAPH. VARYING SOLUTIONS ALSO SHOW
UP WITH THE POTENTIAL SHORTWAVE DROPPING SEWD BEHIND OUR LARGE
UPPER LOW TUESDAY OR WEDNESDAY. ECMWF HAS BEEN PRETTY CONSISTENT
WITH THIS SYSTEM DROPPING SE ACROSS US TUESDAY. THE GFS IS
TRENDING THIS WAY BUT IS ABOUT A DAY SLOWER. WILL FOCUS ON OUR BIG
RAIN AND HIGHER SNOW EVENT OVER THE WEEKEND AND STICK WITH THE
GOING FCST FOR THIS NEXT EVENT. BOTTOM LINE...VERY WARM...DRY
WEATHER COMES TO A SCREECHING HALT LATER FRIDAY THROUGH THE
WEEKEND WITH SIGNIFICANT LOWER ELEVATION RAIN WITH THE PEAK AROUND
FREMONT COUNTY AND 1 TO 2 FEET OF SNOW ABOVE 10K FEET OR SO IN THE
WINDS. AHEAD OF THE UPPER LOW...WE SEE THE POTENTIAL FOR HIGHER
BASED GUSTY THUNDERSTORMS IN THE WEST THURSDAY AFTERNOON WITH
40-50 MPH WINDS VERY POSSIBLE WITH ISOLD SVR GUSTS NOT OUT OF THE
QUESTION. ON FRIDAY WITH THE FRONT COMING DOWN...THOSE AREAS IN
CENTRAL WYOMING START TO COOL WITH GRADUALLY INCREASING SHOWER
POTENTIAL FROM SW TO NE. SOUNDINGS STILL SHOWING STRONG TO SVR
TSTM POTENTIAL IN THE SWRN AND SRN AREAS INCLUDING
KJAC...KBPI...KRKS AND POSSIBLY AS FAR NORTH AS KLND/KRIW OVER TO
KCPR. THOSE LATTER AREAS ARE TURNING COOLER BUT STILL SHOW SOME
MODEST SHEAR AND DECENT CAPES. CAPES EVEN HIGHER FURTHER SOUTH IN
WARMER AIR. SHEAR NOT SHOWING QUITE AS STRONG AS YESTERDAY BUT
AVAILABLE CAPES OF 800-1200J/KG ARE LOOKING POSSIBLE. AFTER
THAT...MORE AND MORE RAIN WITH SOME EMBEDDED THUNDERSTORMS
POSSIBLE LATER FRIDAY NIGHT THROUGH SATURDAY NIGHT.

&&

.AVIATION.../00Z ISSUANCE/

WEST OF THE CONTINENTAL DIVIDE...KJAC/KRKS/KPNA/KBPI AIRPORTS

CONDITIONS WILL REMAIN VFR THROUGH THE FORECAST PERIOD. INCREASING
SOUTH-TO-SOUTHWEST FLOW AHEAD OF THE UPPER LOW APPROACHING THE
CALIFORNIA COAST WILL SPREAD MID-LEVEL MOISTURE ACROSS WESTERN
WYOMING THURSDAY. ENOUGH MOISTURE TO GENERATE CONVECTION OVER THE
HIGHER TERRAIN AFTER 19Z/THURSDAY. HAVE INCLUDED VCSH AT KJAC AND
KBPI TO ACCOUNT FOR CONVECTION MOVING OFF THE HIGHER TERRAIN. EXPECT
SOUTH-SOUTHWEST WIND TO INCREASE BY EARLY THURSDAY AFTERNOON WITH
SPEEDS 9-15KTS. KRKS WINDS WILL BE ABOUT 5KTS HIGHER.

EAST OF THE CONTINENTAL DIVIDE...KCPR/KCOD/KRIW/KWRL/KLND AIRPORTS

CONDITIONS WILL REMAIN VFR THROUGH THE FORECAST PERIOD. LEADING
EDGE OF INCREASING MOISTURE FROM THE SOUTH-SOUTHWEST WILL REACH
CENTRAL WYOMING BY THURSDAY AFTERNOON. CONVECTION WILL GENERALLY
BE CONFINED TO THE HIGHER TERRAIN WITH VCSH ONLY NEEDED AT KCOD
THURSDAY AFTERNOON. ONLY TERMINAL WITH WIND OF SIGNIFICANCE WILL BE
KCPR. SOUTHWEST WIND AROUND 10KTS WILL HOLD STEADY OVERNIGHT. THIS
WIND WILL INCREASE AGAIN BETWEEN 14Z-16Z/THURSDAY WITH SPEEDS
14G20KTS ANTICIPATED. OTHER TERMINALS WILL SEE INCREASING SOUTH OR
EVEN SOUTHEAST FLOW DURING THE AFTERNOON WITH SPEEDS 6-10KTS.
&&

.FIRE WEATHER...

MAINLY DRY AND WARM CONDITIONS WILL CONTINUE THROUGH THURSDAY
MORNING FOR ALL AREAS. RELATIVE HUMIDITY WILL FALL INTO THE TEENS
FOR MANY LOWER ELEVATION LOCATIONS...BUT WINDS SHOULD REMAIN LIGHT
TO MODERATE. THE CHANCE OF SHOWERS WILL INCREASE IN THE WEST
THURSDAY AFTERNOON WITH A CHANCE OF THUNDERSTORMS FOR ALL AREAS ON
FRIDAY. A WETTING RAIN IS A GOOD POSSIBILITY FOR MANY AREAS FROM
FRIDAY NIGHT INTO THE WEEKEND. EXPECT MAINLY FAIR MIXING CONDITIONS
AND SMOKE DISPERSAL TODAY WITH FAIR TO GOOD SMOKE DISPERSAL THURSDAY.

&&

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

&&

$$

SHORT TERM...PS
LONG TERM...PS
AVIATION...CNJ
FIRE WEATHER...PS


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