Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 160958
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
358 AM MDT SAT AUG 16 2014

.SHORT TERM...TODAY THROUGH MONDAY NIGHT

WV IMAGERY SHOWING MODEST RIDGING OVR WY W/ LG CLOSED LOW LIFTING
NEWD FROM THE PAC NW INTO SWRN CANADA. EMBEDDED SW ON THE SOUTH END
OF THE LOW IS CURRENTLY MOVING EWD THRU THE NE CORNER OF THE STATE.
MUCH DRIER AIR LOCATED TO THE SW OF THE FA INTO THE CNTRL GREAT
BASIN MOVING THIS WAY AS MAIN UPR HI...CENTERED FAR SOUTH OVR THE
DESERT SW...CONTINUES TO SLOWLY MIGRATE WWD. AT THE SFC...GENERAL
DIFFUSE HI P STILL ACROSS THE ROCKY MOUNTAIN STATES.

TODAY...TRANSITION TO UPR ZONAL FLOW AS THE FA CONTINUES TO DRY OUT
AND WINDS BECOME QUITE UNIDIRECTIONAL VERTICALLY OUT OF THE W. THIS
WIND PROFILE WITH EXTREME DRY LAPSE RATES INCREASING TO BETWEEN 11
TO 13 BY THE AFTERNOON...WILL EASILY BRING DOWN SLIGHTLY STRONGER
WINDS FROM ALOFT CREATING QUITE GUSTY CONDITIONS ACROSS THE
MOUNTAINS AND THE SRN ZONES AS WINDS INCREASE OUT OF THE W. THIS
ALONG WITH RH VALUES BOTTOMING OUT IN THE LOWER TEENS WILL CREATE A
MODERATE RED FAG DAY ACROSS MAINLY SWEETWATER COUNTY. ATTM...SRN
LINCOLN COUNTY LOOKS IT WILL REMAIN AOA CRITICAL LVLS...SO WILL NOT
INCLUDE LINCOLN AT THIS TIME. ADDITIONALLY...THERE WILL NOT BE MUCH
OF A CHC FOR PRECIP ANYWHERE...BUT W/ ONLY THE SMALLEST OF CHANCES
ACROSS THE FAR NRN MOUNTAINS.

SUNDAY AND MONDAY...ZONAL FLOW CONTINUES SUNDAY WITH A MINOR
EMBEDDED SW BEING DRAGGED THRU THE FA BY AFTERNOON. THIS WILL ONLY
SLIGHTLY INCREASE CONVECTIVE PRECIP CHCS AS THE ATMOSPHERE WILL BE
QUITE DRY EVERYWHERE WITH PWS LARGELY AOB 0.50. MDLS DO SHOW A VERY
LOW INCREASE IN MID LVL MOISTURE...BUT MOSTLY NOT ENOUGH TO PRODUCE
MUCH OF ANYTHING OUTSIDE OF THE MOUNTAINS AND EVEN THEN QPF VALUES
WILL BE NEXT TO NOTHING. MONDAY...TRANSITION TO UPR DIRTY RIDGING
BEGINS WITH A MODEST ATTEMPT AT THE MONSOON TRYING TO RETURN. SO
SOMEWHAT INCREASED LOW END PRECIP CHCS BY MONDAY AFTERNOON. WITH LOW
PRESSURE BUILDING INTO THE S/SW...LL FLOW WILL BE OUT OF THE N/NE
ACROSS MUCH OF THE AREA WHILE THE UPR FLOW REMAINS OUT OF THE WEST
AND INCREASING...SO DEEP SHEAR VALUES WILL INCREASE TO ABOVE 30-35
KTS. HOWEVER DEEP MOISTURE WILL NOT BE PRESENT YET...PROBABLY
HOLDING OFF FOR AT LEAST ONE MORE DAY. BUT...STORMS WILL TRY TO
ORGANIZE TO SOME EXTENT...MOST LIKELY ONLY PRODUCING STRONG WIND
GUSTS WITH MOSTLY SMALL HAIL.

.LONG TERM...TUESDAY THROUGH SATURDAY

TUESDAY WILL SEE SOME MID AND UPPER LEVEL MOISTURE MOVE ACROSS THE
AREA. THIS WILL LEAD TO HIGH BASED SHOWERS AND STORMS OVER MUCH OF
THE REGION IN THE AFTERNOON AND EVENING. SOUTHWEST FLOW ALOFT FOR
WEDNESDAY AHEAD OF A WEATHER SYSTEM MOVING THROUGH THE PACIFIC NW
PER THE ECMWF MODEL. THE GFS IS SLOWER WITH THIS SYSTEM BUT KEEPS SW
FLOW ALOFT OVER THE AREA. WILL KEEP ISOLATED SHOWERS AND STORMS IN
MOST MOUNTAINS AND FOOTHILLS AS THERE LOOKS TO BE MOISTURE AROUND
FOR SOME CONVECTION. THE 00Z ECMWF AND 00Z GFS MODELS ARE DIFFERENT
FROM THURSDAY THROUGH SATURDAY. THE GFS GOES BACK TO DIGGING A
TROUGH OVER THE PACIFIC NW AND THEN SENDING IMPULSES THROUGH A SW
FLOW ALOFT THAT IMPACT MAINLY THE WEST AND NORTH. GFS ALSO TAKES AN
UPPER LOW FROM SOUTHERN CALIFORNIA AND EJECTS IT NORTHEAST AND OPENS
IT UP FRIDAY INTO SATURDAY. THE ECMWF MODEL KEEPS THE FLOW
PROGRESSIVE THURS THROUGH SATURDAY. IT HAS A FAIRLY DRY PATTERN FOR
THURS AND FRI WITH ISOLATED SHOWERS AND STORMS FOR THE NW AND FAR
NORTH. THEN THE ECMWF BRINGS IN A WEATHER SYSTEM FOR NEXT SATURDAY.
THAT TIMING MAY BE IN QUESTION. THE GEM MODEL IS CLOSER TO THE ECMWF
THAN THE GFS BUT LACKS THE WEATHER SYSTEM NEXT SATURDAY. HAVE OPTED
TO SIDE WITH THE ECMWF MODEL FOR THURS AND FRI...THEN LOW PRECIP
CHANCE FOR NEXT SATURDAY. FOR HIGH TEMPS...WARM TO HOT TUESDAY. WENT
A FEW DEGREES COOLER WED DUE TO MORE CLOUDS AROUND AND SLIGHTLY
COOLER 700MB TEMPS. ECMWF BRINGS A COOL FRONT INTO NORTHERN WY WED
NIGHT LEADING TO SLIGHTLY COOLER HIGHS THURSDAY IN THE NORTH. HIGHS
IN THE CENTRAL AND SOUTH THURSDAY WILL BE AT OR SLIGHTLY WARMER
THAN WED HIGHS. STILL SEASONALLY WARM ON FRIDAY...THEN COOLER
SATURDAY IF THE ECMWF MODEL COMES TRUE.

&&

.AVIATION.../12Z ISSUANCE/

OVERALL A VERY QUIET AVIATION DAY EXPECTED. SKC CONDITIONS IN THE
MORNING...WITH SOME HIGH BASED CUMULUS IN THE AFTERNOON...WITH A
LIGHT TO BREEZY WEST TO NORTHWEST WIND IN MOST PLACES. THE ONLY
EXCEPTIONS COULD BE SOME VERY LOCALIZED FOG...MAINLY OUT WEST...BUT
NOT ENOUGH CONFIDENCE TO EVEN INSERT VCFG AT ANY TERMINAL. ALSO VERY
ISOLATED CONVECTION COULD OCCUR OVER THE FAR NORTH.

&&

.FIRE WEATHER...

RED FLAG CONDITIONS FOR SWEETWATER COUNTY...ZONE 279...AS FIRE
WEATHER CONCERNS BEGIN TO INCREASE WHILE THE REGION GETS CUT OFF
FROM THE MONSOON MOISTURE FOR A FEW DAYS AND DEEP DRY WESTERLY FLOW
FILLS IN ACROSS THE REGION FROM THE GREAT BASIN. THESE WEST WINDS
WILL GUST 25 TO 30 MPH IN THE AFTERNOON AND MINIMUM RH VALUES WILL
DROP INTO THE LOWER TEENS TO UPPER SINGLE DIGITS WHILE HIGH TEMPS AT
THE LOWER ELEVATIONS WILL RISE INTO THE MIDDLE 80S. ELSEWHERE...FIRE
DANGER WILL CERTAINLY BE ENHANCED TODAY WITH WARMER AND DRIER
CONDITIONS EVERYWHERE. HOWEVER...THE COMBINATION OF BOTH STRONGER
WINDS AND LOW RH VALUES WILL NOT COINCIDE AS THEY DO ACROSS THE
SOUTHERN ZONES. SUNDAY...WARM...DRY...BUT PROBABLY NOT QUITE AS
WINDY/BREEZY...WEATHER CONTINUES. HOWEVER WILL HAVE TO WATCH NATRONA
COUNTY FOR POSSIBLE NEAR RED FLAG CONDITIONS.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING WYZ279.

&&

$$

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






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