Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 171734
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1134 AM MDT SUN AUG 17 2014

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT

WV IMAGERY SHOWING NEAR ZONAL FLOW ACROSS WY W/ TAIL END UPR WAVE
ASSOCIATED WITH CLOSED LOW TO THE N IN SRN CANADA...DEEPENING
DEVELOPING TROF W OVR THE PAC NW COASTAL REGION...AND UPR HIGH ON
TOP OF THE DESERT SOUTHWEST. CURRENT SFC PATTERN CONTINUES WEAK
DIFFUSE PRESSURE FIELD W/ STRONGER P FIELDS WELL N AND S OF THE
REGION.

TODAY...MOSTLY ZONAL FLOW CONTINUES TODAY WITH A MINOR EMBEDDED SW
BEING DRAGGED THRU THE NRN FA BY AFTERNOON. WINDS CONTINUE NEARLY
UNIDIRECTIONAL WITH DEPTH OUT OF THE W. THIS WIND PROFILE WITH
CONTINUED VERY HIGH DRY LAPSE RATES BETWEEN 10 AND 13 BY THE
AFTERNOON...WILL EASILY BRING DOWN STRONGER WINDS FROM ALOFT
CREATING QUITE GUSTY WRLY WIND CONDITIONS ACROSS THE MOUNTAINS IN
ADDITION TO THE CNTRL AND SRN ZONES. THIS ALONG WITH RH VALUES
BOTTOMING OUT IN THE LOWER TEENS WILL CREATE A MODERATE RED FAG DAY
ACROSS PORTIONS OF FREMONT AND SWEETWATER COUNTIES AND MOST OF
NATRONA COUNTY. ADDITIONALLY...THERE WILL NOT BE MUCH OF A CHC FOR
PRECIP ANYWHERE...BUT ONLY THE SMALLEST OF CHANCES ACROSS/NEAR THE
FAR NRN MOUNTAINS AND PERHAPS OVER PARTS OF THE EXTREME SOUTH WHERE
THERE IS SLIGHTLY BETTER MOISTURE AND A FEW STORMS MAY MAKE IT OFF
THE HIGHER TERRAIN OF NRN UT. OTHERWISE...THE ATMOSPHERE WILL BE
MOSTLY VERY DRY WITH PWS LARGELY AOB 0.50.

MONDAY...TRANSITION TO UPR DIRTY RIDGING WITH WY UNDER INCREASINGLY
NW FLOW WITH A BEGINNING ATTEMPT AT MONSOON MOISTURE TRYING TO
RETURN NWD. SO INCREASED LOW END PRECIP CHCS...RELATIVE TO THIS
WEEKEND...BY THE AFTERNOON. WITH LOW PRESSURE BUILDING INTO THE
S/SW...LL FLOW WILL BE UPSLOPE AND OUT OF THE N/NE ACROSS MUCH OF
THE AREA WHILE THE UPR FLOW REMAINS OUT OF THE WEST AND ON THE
INCREASE. DEEP SHEAR VALUES WILL ALSO INCREASE TO ABOVE 30-35 KTS IN
AREAS ACROSS THE NRN ZONES. HOWEVER DEEP MOISTURE WILL NOT BE
PRESENT YET...HOLDING OFF UNTIL TUE. HOWEVER...STORMS WILL TRY TO
WEAKLY ORGANIZE TO SOME EXTENT...MOST LIKELY PRODUCING STRONG WIND
GUSTS...WITH SMALL HAIL IN STORMS TO THE NORTH.

TUESDAY...UPR RIDGING OVR THE FA WILL GET BUSTED THRU THE DAY WITH
THE ARRIVAL OF A RELATIVELY STRONG UPR WAVE BEING SQUEEZED OUT THRU
THE INTERACTION OF THE PLUNGING WRN CONUS LOW P TROF AND THE UPR
HIGH OVR THE SRN ROCKIES...BEING DIRECTED INTO WY. THE SFC WILL
RESPOND W AND DEVELOPING/EVOLVING SFC LOW ENTERING THE STATE FROM
THE SW WITH A SFC BOUNDARY/TROF EXTENDING FROM THE LOW IN THE SW UP
THRU NERN WY. THE POSITIONING OF ALL THESE UPR AND LWR PRESSURE
FIELDS WILL ALSO DIRECT MONSOONAL MOISTURE BACK INTO THE STATE. ALL
BECOMES MAXIMIZED BY LATE AFTERNOON AND THRU THE OVERNIGHT PERIOD
WITH PRECIP BECOMING LIKELY. A FEW STRONG STORMS MAY BE FOUND TUE
AFTERNOON OVR THE ERN COUNTIES THAT CAN TAKE ADVANTAGE OF MAX
WARMING AHEAD OF THE CLOUDS...INCREASING MOISTURE...E TO SE FLOW
INTO THE AREA AND REASONABLE DEEP SHEAR. THESE STORMS COULD PRODUCE
STRONG WINDS AND MARGINAL SVR HAIL EARLY. THRU THE EVENING AND
OVERNIGHT...ATMOSPHERE BECOMES INCREASINGLY TROPICAL WITH PERIODS OF
HEAVY RAIN AND MORE ISOLATED THUNDER...ESPECIALLY ACROSS THE WRN TO
CNTRL ZONES. A FLASH FLOOD WATCH MAY NEED TO BE ISSUED FOR PORTIONS
OF THE FA FOR TUE THRU WED MORNING. WILL CONTINUE TO MONITOR FOR
THIS POSSIBILITY.

.LONG TERM...WEDNESDAY THROUGH SUNDAY

LONG RANGE MODELS ARE IN BETTER AGREEMENT WITH THEIR 00Z RUNS FOR
WED THROUGH NEXT SUNDAY. WEDNESDAY LOOKS WARM AND BREEZY WITH A
CHANCE OF SHOWERS AND STORMS OVER THE WEST AND NORTH...ISOLATED
ACTIVITY CENTRAL AND SOUTH. A COLD FRONT WILL PUSH INTO NORTHERN WY
WED NIGHT WITH SHOWERS AND ISOLATED STORMS POSSIBLE UP NORTH. THE
WEATHER PATTERN TURNS A LITTLE UNSETTLED THURSDAY THROUGH SATURDAY
AS A TROUGH DEVELOPS OVER THE NORTHERN U.S. FROM THE PACIFIC NW TO
NEAR THE GREAT LAKES. THE GFS/ECMWF/GEM MODELS ALL HAVE TIMING
DIFFERENCES WITH WEATHER DISTURBANCES IN THIS FLOW PATTERN. THERE
LOOKS TO BE A SYSTEM PASSING THROUGH FRIDAY AFTERNOON INTO FRIDAY
NIGHT AND THEN A SECOND ONE SATURDAY NIGHT INTO NEXT SUNDAY. THE
OTHER DIFFERENCE IS THE AMOUNT OF COLD AIR THAT WOULD COME DOWN
WITH THE SYSTEMS. THE ECMWF IS COLDER WITH 700MB TEMPS THAN THE
GFS. WILL BLEND THE TWO AND USE THAT FOR FORECASTING HIGH TEMPS.
AT THIS POINT A DAILY CHANCE OF SHOWERS AND STORMS OVER AND NEAR
THE MOUNTAINS AND THE NORTH FOR THURSDAY THROUGH SATURDAY. WILL
ADD A CHANCE OF SHOWERS AND ISOLATED STORMS TO MOST LOWER
ELEVATIONS SATURDAY PM AND NIGHT WITH THE SECOND SYSTEM. WILL KEEP
ISOLATED SHOWERS/STORMS IN THE MOUNTAINS AND ADJACENT FOOTHILLS
FOR NEXT SUNDAY. EXPECT BREEZY TO LOCALLY WINDY CONDITIONS THURS
THROUGH NEXT SUNDAY AS THIS WEATHER PATTERN WOULD FAVOR WY WIND.
AS FOR TEMPS...THURSDAY WILL BE A LITTLE COOLER...THEN A GRADUAL
COOLING TREND FRIDAY AND SATURDAY. NEXT SUNDAY MAY SEE HIGHS MORE
LIKE MID SEPTEMBER THAN MID TO LATE AUGUST...A PREVIEW OF FALL?

&&

.AVIATION.../18Z ISSUANCE/

GENERALLY VFR CONDITIONS EXPECTED TODAY UNDER A CONTINUED AREA OF
HIGH PRESSURE. HOWEVER SOME ISOLATED ACTIVITY MAY BE FOUND ACROSS
PORTIONS OF NORTHERN WYOMING..MAINLY OVER THE MOUNTAINS. SOME
GUSTY WIND WILL APPEAR ACROSS KRIW...KLND...KRKS...AND KCPR
TODAY...MAINLY AFTER 19Z. WIND SHOULD AGAIN WEAKEN DURING THE
EVENING HOURS...WITH BENIGN CONDITIONS OVERNIGHT. CLOUD COVER WILL
BUILD OVER THE CENTRAL AND WESTERN MOUNTAINS AFTER 12Z MONDAY AS A
PUSH OF MOISTURE BEGINS TO INFLUENCE THE AREA.

&&

.FIRE WEATHER...

RED FLAG CONDITIONS FOR ZONES 279...280...283...289...AND 300 AS
FIRE WEATHER CONCERNS INCREASE ONCE AGAIN WITH DRY WESTERLY FLOW
ACROSS THE REGION. 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 TO NEAR 90. ELSEWHERE...FIRE DANGER WILL
CONTINUE ENHANCED WITH WARM AND DRY CONDITIONS NEARLY EVERYWHERE.
HOWEVER...THE COMBINATION OF BOTH STRONGER WINDS AND LOW RH VALUES
WILL NOT COINCIDE AS THEY DO ACROSS THE CENTRAL AND SOUTHERN ZONES.
MONDAY WILL SEE IMPROVING CONDITIONS REGION WIDE AS MONSOONAL
MOISTURE BEGINS TO HEAD BACK INTO THE FORECAST AREA. THE SOUTHERN
ZONES WILL REMAIN QUITE DRY...HOWEVER WINDS WILL BEGIN TO WEAKEN.
TUESDAY...MOISTURE CONTINUES TO SLOWLY INFILTRATE THE STATE WITH
INCREASING RAINFALL STATEWIDE BY EVENING.


&&

.RIW WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING
WYZ279-280-283-289-300.

&&

$$

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




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