National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS65 KRIW 030545
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1045 PM MST SUN MAR 2 2014

.SHORT TERM...TONIGHT THROUGH MONDAY

SOME PACIFIC MOISTURE IN WEST/ZONAL FLOW WILL BRING INCREASED
AREAS OF SNOW TO THE WESTERN MOUNTAINS AND VALLEYS OF WYOMING
TONIGHT. EAST OF THE CONTINENTAL DIVIDE...DOWN SLOPE WINDS ALONG
AND NEAR THE EAST SLOPES WILL CAUSE SOME WARMING IN THE FOOTHILLS
AND OVER THE WESTERN PARTS OF THE BASINS. THE COLD AIR WILL BE
MODIFIED BUT THE AMOUNT OF WARMING IN THE DEEPEST PARTS OF THE
BASINS ALONG THE RIVERS IS VERY DIFFICULT TO DETERMINE. SOME AREAS
IN THE BIG HORN BASIN AND NORTHERN WIND RIVER BASIN MAY BE MUCH
COLDER THAN FORECAST...WHILE THE WINDIER AREAS MAY CONVERSELY BE
MUCH WARMER THAN FORECAST. THE PLAINS OF EASTERN JOHNSON AND
NATRONA COUNTIES...WHERE THERE IS NO TERRAIN TO BLOCK THE
DEVELOPING SOUTHWEST FLOW MAY SEE THEM MOST DRAMATIC WARM UP WITH
TEMPERATURES WARMING 25 TO 30 DEGREES IN AN HOUR ONCE THE WINDS
MIX DOWN. MORE SNOW IN THE WEST FOR MONDAY WITH VARIABLE CLOUDS
EAST AND INCREASING BREEZY TO WINDY AREAS AND CONTINUED WARMING.
SOME OF THE WESTERN VALLEYS MAY SEE RAIN...ESPECIALLY BELOW 7500
FEET. HAVE ISSUED A SPECIAL WEATHER STATEMENT FOR THE SNOWFALL
ACROSS THE WEST TONIGHT...EXPECTING MOST AREAS TO BE BELOW WINTER
WEATHER ADVISORY CRITERIA. SNOWFALL MONDAY AND MONDAY NIGHT COMBINED
MAY REQUIRE AN ADVISORY.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

THE SNOW HOSE COMING OFF THE PACIFIC WILL CONTINUE TO FEED SNOWFALL
TO FAR WESTERN WYOMING MONDAY NIGHT THROUGH TUESDAY EVENING. SOME Q
VECTOR FORCING ASSOCIATED WITH A WEAK VORT LOBE WILL LIKELY ENHANCE
SNOWFALL SLIGHTLY ON TUESDAY ALONG WITH INSTABILITY GIVEN THE
NEGATIVE LIFTED INDICES WITH WEAK COOL AIR ADVECTION AT H7. AN
ASSOCIATED WEAK SURFACE LOW/TROUGH WILL SET UP SHOP OVER CENTRAL WY
TUE AND TUE NIGHT ALLOWING A FEW RAIN/SNOW SHOWERS TO SPILL OVER THE
DIVIDE...ESP IN SOUTHERN WY TUE EVE. A HIGH PRESSURE RIDGE WILL
ACTUALLY BUILD OVERHEAD FROM THE WEST FOR DRY WEATHER EVERYWHERE
WEDNESDAY...IF NOT BRIEFLY...AS THE FLOW BUCKLES AND A DOWNSTREAM
TROUGH DEEPENS OVER THE MIDWEST TO OUR EAST. THEN A DEEPENING
UPSTREAM SHORTWAVE TROUGH WILL APPROACH WY FROM THE WEST DURING THE
LATTER PORTION OF THE WEEK. AHEAD OF THE TROUGH...SOME ISENTROPIC
LIFT WILL GET UNDERWAY WITH SNOW REDEVELOPING IN THE WEST LATER
WEDNESDAY NIGHT. THURSDAY IS SHAPING UP TO BE THE APEX OF THIS NEXT
PRECIP EVENT WITH THE RIDGE FLATTENING AND THE AIR MASS
DESTABILIZING. THE SNOW WILL MIX WITH RAIN IN THE WEST AS MILDER AIR
STREAMS IN FROM THE WEST AS THE JET STREAM SHIFTS TO THE NORTH OF
WYOMING. ON THURSDAY NIGHT THE PRECIP WILL SPILL EAST OF THE DIVIDE
AS RIGHT REAR QUAD DYNAMICS COME INTO PLAY WITH THE AFOREMENTIONED
JET AND AN ASSOCIATED COOL FRONT SWEEPS THROUGH WITH A SURFACE LOW
TRACKING SOUTHEAST ACROSS JOHNSON COUNTY WITH EQUAL CHANCES OF
PRECIP ON BOTH SIDES OF THE DIVIDE AFTER MIDNIGHT. THEN ON FRIDAY A STRONGER
COLD FRONT AND ASSOCIATED SHORTWAVE TROUGH WILL FOLLOW ON THE FIRST
ONES HEELS AND WILL CONTINUE TO GIVE AREAS EAST AND WEST OF THE
DIVIDE AN EQUAL CHANCE OF PRECIP. FLAT HIGH PRESSURE WILL BUILD IN
FOR NEXT WEEKEND FOR A TREND TOWARD DRIER CONDITIONS. WITH THE
WESTERLY WINTER LIKE PROGRESSIVE FLOW PATTERN CONTINUING...BRISK
WEST SOUTHWEST WINDS ARE FORECAST FOR MUCH OF NEXT WEEK ALONG THE
SOUTHERN WIND CORRIDOR AND ALONG THE EAST SLOPE OF THE
DIVIDE...ESPECIALLY ON WEDNESDAY NIGHT WHEN H7 WEST WINDS WILL BE 50
KNOTS. TEMPS WILL COOL OFF SLIGHTLY BEHIND TUESDAYS WEAK WEATHER
SYSTEM...THEN WARM UP THROUGH MID WEEK WITH H7 TEMPS INCREASING TO
BETWEEN 2C AND 3C THURSDAY WHEN PLENTY OF HIGHS IN THE 50S WILL
OCCUR AT THE LOWER ELEVATIONS EAST OF THE DIVIDE. THEN A COOL DOWN
DURING AND AFTER THE PRECIP EVENT THURSDAY/FRIDAY BEFORE WARMING
BACK UP QUICKLY NEXT WEEKEND WHEN THE FLAT RIDGE MOVES IN OVER THE
AREA. THERE IS ONLY A SLIGHT CHANCE OF PRECIP IN THE NORTHERN MTNS
SUNDAY AFTERNOON AS THE FLOW BACKS TO A MORE WESTERLY TRAJECTORY OFF
THE PACIFIC BEHIND THE EXITING FLATTENING RIDGE.

&&

.AVIATION.../06Z ISSUANCE/

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

LOWER ELEVATIONS WILL BE DRY WITH VFR CONDITIONS THROUGH THE
FORECAST PERIOD WITH VARIABLE MID/HIGH LEVEL CLOUDINESS. SOME LOW
LEVEL WIND SHEAR WILL OCCUR THROUGH MID MORNING MONDAY IN THE FOOTHILLS
INCLUDING AT KCOD AND KLND TERMINALS. MOUNTAINS WILL HAVE PERIODS OF
SNOW WITH MVFR/IFR CONDITIONS...ESPECIALLY ALONG THE DIVIDE...WITH
LESS OF AN IMPACT OVER THE BIG HORN MOUNTAINS. BASINS AND VALLEYS
WILL SEE FAIRLY LIGHT WINDS THROUGH THE PERIOD WHILE THE
MOUNTAINS...THE WIND CORRIDOR FROM SOUTH PASS TO KCPR...AS WELL AS
DUBOIS WILL BE BREEZY TO WINDY AT TIMES.

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

SNOW SHOWERS WILL CONTINUE ACROSS WESTERN MOUNTAINS AND FAR WESTERN
VALLEYS AT TIMES...WITH LITTLE ACTIVITY...BUT ENOUGH FOR VCSH IN THE
UPPER GREEN RIVER BASIN AND SWEETWATER COUNTY THROUGH MUCH OF THE
TAF FORECAST PERIOD. THE SNOW COULD MIX WITH OR CHANGE TO RAIN IN
THE LOWER ELEVATIONS AT TIMES. WILL KEEP KJAC ALL SNOW FOR NOW...BUT
TEMPERATURES IN THE LOWER TO MID 30S WILL KEEP RUNWAYS MAINLY
WET...EXCEPT RIGHT AFTER A BURST OF HEAVIER SNOW. THE BEST SHOT FOR
SNOWFALL WILL OCCUR THROUGH ABOUT 16Z MONDAY...AND THEN AGAIN TONIGHT.
MOUNTAINS WILL BE OBSCURED MUCH OF THE TIME. BREEZY SOUTHERLY WINDS
ARE EXPECTED...MAINLY LATE MONDAY MORNING INTO THE AFTERNOON AT
KJAC...WITH WINDY WEST WIND DEVELOPING ACROSS SWEETWATER COUNTY.

&&

.FIRE WEATHER...

NO FIRE WEATHER CONCERNS ARE EXPECTED THROUGH THE WEEK.
LOW MIXING HEIGHTS WITH POOR SMOKE DISPERSAL EXPECTED WITH INVERSIONS
MOST AREAS. WINDIER AREAS IN THE FOOTHILLS MAY SEE LOCAL FAIR
SMOKE DISPERSAL WITH BETTER MIXING. DRY WEATHER IS EXPECTED EAST
OF THE CONTINENTAL DIVIDE WITH A GRADUAL WARMING TREND. OCCASIONAL
SNOW WILL CONTINUE ACROSS THE WEST INTO EARLY NEXT WEEK.

&&

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

&&

$$

SHORT TERM...C.BAKER
LONG TERM...LIPSON
AVIATION...WM
FIRE WEATHER...C.BAKER