Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 280855
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
255 AM MDT SAT MAR 28 2015

.SHORT TERM...SATURDAY THROUGH MONDAY NIGHT

SATURDAY STILL LOOKS TO BE THE MOST ACTIVE OF THE NEXT FEW DAYS. THE
CULPRITS ARE A VIGOROUS TROUGH AS WELL AS AN ASSOCIATED COLD FRONT
CURRENTLY LOCATED OVER WASHINGTON AND OREGON THAT WILL RACE ACROSS
THE AREA THIS AFTERNOON AND TONIGHT. THERE IS SOME INSTABILITY AS IT
MOVES ACROSS. HOWEVER...IT IS LACKING DEEP MOISTURE WITH MOST OF
THAT MOVING ACROSS NORTHERN MONTANA AND SOUTHERN CANADA. AS A
RESULT...WE ANTICIPATE ONLY A FEW SHOWERS ACROSS NORTHERN PORTIONS
OF WYOMING THIS AFTERNOON AND EVENING.

HOWEVER...THE BIG STORY WILL BE THE WIND AS HATS AND TOUPEES WILL BE
FLYING AROUND THIS AFTERNOON IF NOT SECURED. THERE ARE 3 FACTORS
THAT WILL COME TOGETHER FOR A WINDY DAY ACROSS MUCH OF THE AREA. THE
FIRST IS THE TIGHT PRESSURE GRADIENT AS LOW PRESSURE DEVELOPS JUST
TO THE NORTH OF THE AREA. THE SECOND IS INCREASING 700 MILLIBAR
WINDS WITH VELOCITIES UP TO 50 TO 60 KNOTS IN MANY AREAS. WITH GOOD
MIXING EXPECTED WITH THE FRONTAL PASSAGE THESE WILL LIKELY MIX TO
THE SURFACE. IN ADDITION...THE AREA WILL BE IN THE FAVORED RIGHT
FRONT QUADRANT OF A 90-95 KNOT JET STREAK THIS AFTERNOON THAT WILL
ENHANCE DOWNWARD MOMENTUM. WITH THESE CONDITIONS...WE WILL UPGRADE
THE HIGH WIND WATCH TO A WARNING WITH THE ISSUANCE OF THE PACKAGE
THIS MORNING. THE MOST FAVORED AREA IS ACROSS NORTHERN JOHNSON
COUNTY WHICH IS FAVORED WITH NORTHWESTERLY FLOW AFTER FRONTAL
PASSAGES. ELSEWHERE...WINDS SHOULD FALL SHORT ALTHOUGH STRONG GUSTS
ARE POSSIBLE IN AREAS LIKE THE CODY FOOTHILLS AND EVEN THE WIND
RIVER BASIN. WITH THE DOWNSLOPING FLOW IT WILL ALSO BE A VERY WARM
DAY WITH RECORD HIGH TEMPERATURES A DECENT POSSIBILITY FOR MANY
AREAS. THE RED FLAG WARNING ALSO LOOKS GOOD AND WILL BE CONTINUED AS
IS. THE TIME OF THE STRONGEST WINDS SHOULD LATE THIS AFTERNOON
THROUGH THIS EVENING BEFORE THE FORCING AND PRESSURE GRADIENT
DECREASE.

MAINLY QUIET WEATHER SHOULD RETURN FOR SUNDAY AND MONDAY AS HIGH
PRESSURE AND WEAK RIDGING BUILD BACK OVER THE COWBOY STATE. THERE
COULD STILL BE LOCALLY BREEZY CONDITIONS IN FAVORED AREAS BUT
NOTHING LIKE SATURDAY AFTERNOON. TEMPERATURES WILL ALSO COOL DOWN
SOMEWHAT BEHIND THE FRONT...BUT STILL REMAIN ABOVE NORMAL FOR LATE
MARCH.

.LONG TERM...TUESDAY THROUGH SATURDAY

TUESDAY LOOKS BREEZY TO WINDY AND WARM AHEAD OF THE NEXT WEATHER
SYSTEM. ISOLATED SHOWERS MAY DEVELOP IN FAR WEST WY MID TO LATE
AFTERNOON. AS THE FRONT BLOWS THROUGH WY TUE NIGHT SOME SHOWERS AND
ISOLATED STORMS WILL OCCUR MAINLY OVER THE NORTH AND CENTRAL WITH
ISOLATED ACTIVITY OVER THE SOUTH. EXPECT IT TO BE BREEZY TO WINDY
TUESDAY NIGHT AFTER THE FRONTAL PASSAGE. THE ECMWF MODEL IS A LITTLE
SLOWER WITH THIS FRONTAL PASSAGE. THE GFS KEEPS THE WEATHER
UNSETTLED ACROSS THE NORTH HALF OF THE STATE WEDNESDAY INTO WED
NIGHT WITH SOME SHOWERS AND ISOLATED STORMS. FOR NOW THE ACTIVITY
WOULD BE ALONG AND NORTH OF A LINE FROM JACKSON TO MIDWEST. THE
ECMWF MODEL IS A LITTLE DRIER OVER THE NORTH WED AND WED NIGHT BUT
DOES KEEP NW WY WITH THE BEST CHANCE OF SHOWERS. THE GFS KEEPS
ISOLATED SHOWERS IN THE FORECAST THURSDAY WITH A WEATHER DISTURBANCE
MOVING THROUGH THE AREA. THE ECMWF MODEL HAS MORE OF A DIGGING
TROUGH INTO THE GREAT BASIN THURS INTO THURS NIGHT. THIS LEADS TO A
WETTER SCENARIO OVER THE REGION. HAVE USED A BLEND OF THE SOLUTIONS
AND HAVE A CHANCE OF SHOWERS FOR NOW. THE GFS HAS A WEST FLOW ALOFT
FOR FRIDAY WITH DRY CONDITIONS. THE ECMWF MODEL KEEPS A NW FLOW OVER
THE AREA AND LINGERING ISOLATED SHOWERS. HAVE OPTED TO KEEP IT DRY
AND ONLY ISOLATED SHOWERS OVER THE NW CORNER OF WY. THEN NEXT
SATURDAY THE GFS HAS A WEST TO SOUTHWEST FLOW ALOFT WITH ISOLATED
SHOWERS/STORMS FOR PLACES WEST OF THE DIVIDE. THE ECMWF IS DRY WITH
A BIT OF AN UPPER RIDGE OVER THE REGION. WILL GO WITH ISOLATED
SHOWERS FAR WEST NEXT SATURDAY. AFTER THE WARM AND WELL ABOVE NORMAL
TEMPS TUESDAY...HIGH TEMPS WILL BE COOLER AND MORE TOWARD SEASONAL
VALUES FOR WED THROUGH FRIDAY. THEN A LITTLE WARMER NEXT SATURDAY.

&&

.AVIATION.../12Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH 12Z SUNDAY.  A STRONG BUT MAINLY
DRY COLD FRONT WILL PUSH ACROSS THE AREA THIS AFTERNOON.  A LINE
OF SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO IS EXPECTED TO DEVELOP
AHEAD OF THE FRONT...MOVING RAPIDLY EAST VICINITY AND NORTH OF A
KCOD-KGCC LINE DURING THE AFTERNOON.  THESE SHOWERS ARE EXPECTED TO
BE HIGH-BASED WITH CEILINGS FL120-140...WITH SOME HIGHER MOUNTAIN
OBSCURATIONS ACROSS THE ABSAROKA AND BIGHORN RANGES. STRONG SURFACE WEST
TO NORTHWEST WINDS 25-40 KNOTS WILL BE THE MAIN HAZARD BEHIND THE FRONT
18Z SAT TO AROUND 02Z SUNDAY.  THE STRONGEST WINDS ARE EXPECTED
VICINITY AND NORTH OF INTERSTATE 90.  WINDS WILL GRADUALLY DIMINISH IN
MOST AREAS WITH SUNSET THROUGH THE EVENING...BECOMING LIGHT IN MOST
AREAS AFTER 06Z SUNDAY AS SURFACE HIGH PRESSURE BUILDS IN FROM THE
WEST.

&&

.FIRE WEATHER...

A COLD FRONT AND ASSOCIATED UPPER LEVEL DISTURBANCE WILL BRING A
COMBINATION OF GUSTY TO HIGH WIND...LOW RELATIVE HUMIDITY AND WARM
TEMPERATURES. AS A RESULT EXPECT FIRE DANGER TO INCREASE ACROSS MANY
AREAS WITH A LACK OF SNOW COVER. IN ZONES 283...281 AND 280 WHERE
FUELS ARE CRITICAL THE RED FLAG WARNING WILL BE CONTINUED THROUGH
THIS EVENING. FIRE CONDITIONS SHOULD IMPROVE SUNDAY AND MONDAY WITH
COOLER TEMPERATURES AND LESS WIND.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THIS EVENING
WYZ280-281-283.

HIGH WIND WARNING FROM 3 PM THIS AFTERNOON TO MIDNIGHT MDT
TONIGHT WYZ010-011.

&&

$$

SHORT TERM...HATTINGS
LONG TERM...AR
AVIATION...AEM
FIRE WEATHER...HATTINGS






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