Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 010556
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1152 PM MDT SUN AUG 31 2014

.SHORT TERM...TONIGHT THROUGH MONDAY (ISSUED AT 300 PM MDT)

EXPANDING UPR LVL TROF ACROSS THE CONUS W OF THE MISSISSIPPI...W/
BASE OF TROF SWINGING EWD ACROSS WY TODAY. ANOTHER EMBEDDED SW TROF
MOVING THRU THE CNTRL FA INTO THE ERN PORTIONS OF THE STATE THIS
AFTERNOON. ANOTHER EMBEDDED SW LIES IN WAIT UPSTREAM JUST OFF THE
COAST OF OR/WA...AND WILL RACE INTO WRN/NWRN WY BY MONDAY MORNING.
AT THE SFC...GENERAL HIGH P TO THE W OF THE STATE...LOW P E WITH
FRONT/BOUNDARY BISECTING THE STATE FROM E TO SW CUTTING FROM NRN
NATRONA COUNTY...TO NRN SWEETWATER COUNTY AND W INTO SRN LINCOLN
COUNTY.

TODAY... OVERALL...MUCH COOLER CONDITIONS FROM FRONTAL
PASSAGE AND/OR SIGNIFICANT UPR LVL TEMP DROP AND CLOUD COVER.
CONTINUED  RELATIVELY STRONG GUSTY W TO WSW WINDS ACROSS THE SRN FA
SOUTH OF THE FRONT/BOUNDARY MENTIONED ABOVE...WITH GUSTY N TO NW
WINDS BEHIND THE FRONT. ANOTHER WEAKER FRONT LOOK TO BE LAYING
ACROSS MT AND WILL ENTER THE NRN AND ERN PORTION OF THE FA ON
MONDAY. ISOLATED TO SCATTERED SHOWERS AND ISOLATED THUNDER  ARE
MAKING THEIR WAY ACROSS PORTIONS OF CENTRAL AND EASTERN WY THIS
AFTERNOON...AND WILL CONTINUE AN EWD TRACK...DECREASING FROM W TO E
INTO THE EVENING. STRONGER STORMS WITH SMALL HAIL AND GUSTY WINDS
WILL BE MOST PROBABLE ERN FREMONT AND ACROSS NATRONA COUNTIES
NEAR/ALONG FRONT/BOUNDARY. CAPE AND SHEAR IN THIS AREA ARE 500-700
J/KG AND 25-30 KTS RESPECTIVELY...JUST ENOUGH TO WEAKLY ORGANIZE A
STORM OR TWO.

TONIGHT AND MONDAY...MAIN TROF PASSES E AND INTO THE GREAT PLAINS...UPR
LVL NW FLOW CONTINUES...AND THE OR/WA DISTURBANCE CONTINUES TO HEAD
THIS WAY THRU THE BACKSIDE OF THE LW TROF...ARRIVING NEAR THE WRN
BORDER BETWEEN 06 AND 09Z...THEN TRANSLATING ACROSS THE FA QUICKLY
BY EARLY AFTERNOON.  THIS WILL KEEP A NEARLY CONTINUAL CHC FOR SHRA
GOING ACROSS THE NW FA THROUGH AT LEAST MID TO LATE MORNING
MONDAY...AND ACROSS THE NRN/NERN FA INTO THE AFTERNOON. WHILE THIS
UPR LVL ENERGY WILL EXTEND WELL SOUTH AND OVR MOST OF THE
CWA...RAPID DRYING OF THE ATMOSPHERE WILL OCCUR BEHIND THE PASSAGE
OF THE MAIN TROF AXIS TONIGHT AND THROUGH MONDAY MORNING FROM W TO
E...AND THERE WILL NOT BE MUCH IN THE WAY OF MOISTURE TO ACT ON. A
FEW STRONGER STORMS MAY OCCUR OVR JOHNSON COUNTY BY EARLY AFTERNOON
WHERE SOME USEFUL MOISTURE WILL STILL BE LEFTOVER...CAPE WILL BE
MARGINAL AND SHEAR WILL BE MAXIMIZED ALONG AND NORTH OF A
CLIPPER-LIKE BOUNDARY/FRONT. SNOWFALL WILL BE POSSIBLE AGAIN ACROSS
THE NORTHERN MOUNTAINS...WITH GENERAL 1 INCH ACCUMULATIONS ABOVE
9500 FEET...AND PERHAPS A FEW AREAS ABOVE 10500 FEET RECEIVING UP TO
3 INCHES. NOT EXPECTING MUCH TO STICK TO ANY ASPHALT ROADWAYS
HOWEVER.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY

MONDAY NIGHT AS THE TROUGH CONTINUE TO MOVE EAST...HIGH PRESSURE
RIDGING WILL OCCUR OVER THE PACIFIC NORTHWEST.  THE MAIN TREND WILL
BE FOR DRYING WITH BREEZY TO WINDY CONDITIONS ACROSS THE SOUTH INTO
CENTRAL AREAS.

TUESDAY AND TUESDAY NIGHT DRY HIGH PRESSURE IS EXPECTED TO DOMINATE
THE WEATHER ACROSS THE AREA WITH INCREASING WEST TO SOUTHWEST WINDS
CENTRAL AND SOUTH WITH GENERAL WARMING. TEMPERATURES SHOULD WARM.

WEDNESDAY AND WEDNESDAY NIGHT  SOME MID LEVEL CLOUDS ARE EXPECTED TO
MOVE UP FROM THE GREAT BASIN IN THE AFTERNOON...OTHERWISE THE DRY
HIGH PRESSURE IS EXPECTED TO CONTINUE TO DOMINATE THE WEATHER WITH
CONTINUED SOUTHWEST WINDS ACROSS THE CENTRAL AND SOUTH WITH THE
WARMING TREND CONTINUING.

THURSDAY AND THURSDAY NIGHT  HIGH PRESSURE WILL SHIFT EAST WITH
INCREASING SOUTHWEST FLOW ALOFT BRINGING SOME PACIFIC MOISTURE ALOFT
OVER THE AREA.  SHOWERS ARE EXPECTED TO DEVELOP WITH ISOLATED
THUNDERSTORMS IN THE AFTERNOON...MOST NUMEROUS OVER THE WESTERN AND
CENTRAL MOUNTAINS.  INCREASED CLOUD COVER  AND A COLD FRONT MOVING
SOUTH FROM MONTANA WILL BRING COOLING.  MODELS STRONGER WITH COLD
FRONT THAN YESTERDAY WITH MORE SIGNIFICANT COOLING.

FRIDAY AND FRIDAY NIGHT  SHOWERS AND ISOLATED THUNDERSTORMS ARE
EXPECTED TO INCREASE OVER THE AREA AS PACIFIC MOISTURE INCREASES IN
SOUTHWEST FLOW ALOFT.  A COLD FRONT WILL CONTINUE TO MOVE SOUTH
INTO SOUTHERN WYOMING.  AGAIN MODELS CONTINUE TO BE STRONGER WITH
THIS COLD FRONT AND ASSOCIATED COOLING BRINGING THE COLD AIR THROUGH
THE SOUTHWEST WHILE YESTERDAY THE FRONT DID NOT MIKE IT THROUGH
CENTRAL WYOMING.

SATURDAY AND SATURDAY NIGHT SOUTHWEST FLOW ALOFT WILL REMAIN IN
PLACE OVER THE AREA WITH A STREAM OF PACIFIC MOISTURE CONTINUING TO
ADVECT INTO THE AREA SUPPORTING SCATTERED SHOWERS AND SOME ISOLATED
AFTERNOON THUNDERSTORMS.  A FRONT IS EXPECTED TO REMAIN THROUGH
SOUTHERN WYOMING WITH CONTINUED COOLING.

SUNDAY SOME DRYING IS EXPECTED IN THE WEST WITH POSSIBLE WARMING.
OVERALL LOW CONFIDENCE IN FORECAST FOR SUNDAY AS THE SPREAD IN
SOLUTIONS WITH THE EXTENDED MODELS BECOMES MORE SIGNIFICANT.

&&

.AVIATION.../06Z ISSUANCE/

A LAST IN A SERIES OF UPPER LEVEL DISTURBANCES IN NW FLOW WILL RACE
SE INTO NW WYOMING THIS MORNING AND INTO THE HIGH PLAINS LATE THIS
AFTERNOON.   AREAS OF MVFR/IFR CIGS WITH SCT -SHRA...SNOW LEVELS
NEAR 9.5KFT WITH FRQT MTN OBSCURATIONS ...WILL SPREAD ACROSS
NORTHERN WYOMING FROM YELLOWSTONE NATIONAL PARK TO A VCNTY AND NORTH
OF KCOD-KBYG LINE 09Z-15Z.  MOST OF THIS ACTIVITY WILL PUSH FROM
VCNTY OF THE BIGHORN RANGE AND EASTWARD BY EARLY AFTERNOON.  SOME OF
THIS SHOWER ACTIVITY MAY REACH AS FAR AS KCPR IN THE LATE MORNING
AND AFTERNOON.  W-NW WIND AT 15-25KT AND MAINLY SKC CONDITIONS WILL
PREVAIL ACROSS THE SOUTHERN THIRD OF THE AREA IN THE AFTERNOON.

SKC CONDITIONS WITH DIMINISHING WIND...PATCHY FOG IN THE WESTERN
VALLEYS...WILL PREVAIL MONDAY NIGHT.

&&

.FIRE WEATHER...

FIRE DANGER WILL BE RELATIVELY LOW TODAY THROUGH TONIGHT. A LARGE
UPPER LEVEL TROUGH CONTINUES TO EXPAND ACROSS THE COUNTRY TODAY WITH
ANOTHER EMBEDDED DISTURBANCE MOVING THROUGH THE TROUGH AND ACROSS
WYOMING TODAY...THEN INTO THE HIGH PLAINS BY TONIGHT. ANOTHER
DISTURBANCE WILL FOLLOW BETWEEN BETWEEN MIDNIGHT AND EARLY AFTERNOON
MONDAY...AFFECTING MAINLY THE NORTHERN FORECAST ZONES. A SURFACE
FRONT/BOUNDARY LAYS ACROSS NATRONA COUNTY AND WEST INTO SOUTHERN
FREMONT COUNTY THEN NORTHERN SWEETWATER COUNTY. ISOLATED TO
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE ACROSS
CENTRAL...EASTERN AND NORTHERN WYOMING THROUGH THE AFTERNOON BEFORE
BECOMING MORE ISOLATED IN NATURE FOR MOST LOCATIONS EXCEPT FOR THE
NORTHWEST WHICH WILL CONTINUE MORE SCATTERED. SNOW LEVELS WILL HOVER
BETWEEN 9-10KFT ACROSS THE NORTH. SOUTH OF THE FRONT/BOUNDARY
MENTIONED ABOVE...WEST TO WEST SOUTHWEST WINDS CONTINUE TODAY AT
15-25 MPH WITH GUSTS 35 TO 40 MPH POSSIBLE ALONG WITH MINIMUM RH
VALUES ONLY DROPPING TO 35 PERCENT AT THE LOW END. ISOLATED ERRATIC
OUTFLOW WIND GUSTS NEAR 45KTS WILL BE POSSIBLE WITH A FEW STORMS
THIS AFTERNOON.

&&

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

$$

SHORT TERM...BRAUN
LONG TERM...C.BAKER
AVIATION...BRAUN
FIRE WEATHER...BRAUN








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