Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 200531
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1131 PM MDT SAT APR 19 2014

.SHORT TERM...TONIGHT THROUGH TUESDAY (ISSUED AT 156 PM MDT)

WEAK SHORTWAVE MOVED INTO THE SW THIS MORNING WITH ACCAS AND
SPRINKLES. THIS AREA HAS NOW TURNED INTO LIGHT SHOWERS AND IS
MERGING WITH OUR MOISTURE...LEFTOVER FRONTAL BOUNDARY AND DAYTIME
HEATING TO PRODUCING SOME BUILDING CUMULUS OVER SWEETWATER COUNTY.
IDEA OF MAINLY ISOLATED SHOWERS AND A COUPLE THUNDERSTORMS IS
LOOKING GOOD WITH A FEW MORE OVER THE MOUNTAINS. COUPLE LIGHTNING
STRIKES JUST SOUTH OF THE BORDER SO FAR. NEXT SYSTEM MOVES EWD
AWAY FROM THE UPPER LOW OFF THE B.C. COAST WHICH PUSHES A COLD
FRONT SE ACROSS THE AREA ON EASTER. THE FRONT MAY INTERACT WITH
THE LEFTOVER MOISTURE FROM TODAY`S SYSTEM OVER OUR FAR SERN ZONES
TO PROVIDE ANOTHER DAY OF MAINLY ISOLATED SHOWERS AND PERHAPS A
THUNDERSTORM OR TWO. INSTABILITY LOOKS VERY LIMITED ON
FORECAST/INTERPOLATED SOUNDINGS. OTHERWISE...ANOTHER MILD DAY
WITH TEMPERATURES GENERALLY 60S EAST OF THE DIVIDE AND 50S TO
LOWER 60S WEST. THE MOUNTAINS WILL BE IN THE 40S AND 50S. RIDGE
AXIS MOVES OVERHEAD ON MONDAY WITH SLIGHTLY WARMER TEMPERATURES
YET. COULD BE A FEW SHOWERS TRYING TO DEVELOP OVER THE FAR WEST BY
MONDAY EVENING AS SOME MOISTURE FROM THE ERN FRINGES OF OUR BIG
MIDWEEK SYSTEM WORKS ON A WARM TEMPERATURES MONDAY.
OTHERWISE...MONDAY LOOKS DRY AND MILD TO WARM. TUESDAY WE STILL
OUR BIG NEGATIVELY TILTED UPPER LOW MOVE INTO THE GREAT BASIN WITH
RAPIDLY FALLING PRESSURES AS A SURFACE LOW FORMS OVER MONTANA.
STRONG SLY FLOW WHICH WILL DEVELOP MONDAY NIGHT WILL CONTINUE TO
STRENGTHEN THROUGH THE DAY TUESDAY LEADING TO A WINDY TO VERY
WINDY DAY FOR MOST EVERYONE. COLD FRONT NEAR THE FAR WEST LATE IN
THE DAY WITH A LINE OF SHOWERS AND THUNDERSTORMS QUITE LIKELY OUT
WEST. A FEW OF THESE COULD BE QUITE STRONG EVEN IF IT`S JUST
SHOWERS AND OR THUNDERSTORMS MOVING NWD AND ADDING TO THE AMBIENT
STRONG SLY FLOW PRODUCING VERY STRONG SLY WINDS. EAST OF THE
DIVIDE...DAYTIME HEATING MAY BE ENOUGH FOR ISOLATED SHOWERS AND
THUNDERSTORMS WITH SOME RETURN FLOW MOISTURE AND HIGHER CAPES
POSSIBLE IN JOHNSON COUNTY. OTHERWISE...WARM AND WINDY WITH PCPN
BECOMING FAIRLY WIDESPREAD OUT WEST. SNOW LEVELS WILL BE ABOVE 10K
FEET DURING THE DAY ADDING TO THE RISK OF SOME MODERATE TO LOCALLY
HEAVY RAIN ON DEEP SNOWPACK.

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY

A VIGOROUS SHORTWAVE TRACKING NORTHEAST AROUND THE BASE OF THE DEEP
TROUGH THAT WILL BE SITUATED ALONG THE CANADIAN/PACIFIC NORTHWEST
COAST TUE NT WILL PRODUCE NUMEROUS RAIN AND SNOW SHOWERS IN THE FAR
WEST TUESDAY NIGHT WITH 2 TO 3 INCHES OF ACCUMULATING SNOW AFTER
MIDNIGHT IN THE FAR WEST. SOME ISOLATED THUNDER ALSO POSSIBLE.
PRECIPITATION WILL SPILL OVER TO AREAS EAST OF THE DIVIDE LATER
TUESDAY NIGHT AND INTO WEDNESDAY. WEDNESDAY WILL FEATURE PRECIP
MAINLY IN THE FORM OF RAIN EXCEPT MOSTLY SNOW IN THE MOUNTAINS. BY
WEDNESDAY...THE AFOREMENTIONED TROUGH WILL CLOSE INTO AN ALMOST
VERTICALLY STACKED LOW OVER MONTANA AS IT TRACKS EAST. HIGH TEMPS
WED SHOULD RUN ABOUT 10 TO 20 DEGREES COOLER COMPARED TO TUE.THERE
WILL BE MORE PRECIP ACROSS THE NORTH HALF OF THE CWA WEDNESDAY NIGHT
CLOSER TO THE TRACK OF THE LOW. DURING THE COURSE OF THE NIGHT
WEDNESDAY NIGHT...H7 TEMPS WILL DROP TO -10C WEST OF THE DIVIDE AND
-8C EAST SO THAT BY 06Z THU...MOST OF WHAT PRECIP OCCURS WILL BE IN
THE FORM OF SNOWFALL. BY WEDNESDAY NIGHT...WITH ENOUGH COLD AIR
ALOFT DESTABILIZING THE ATMOSPHERE...EXPECT CONVECTIVE SNOW BANDS TO
FORM OFF SOUTH PASS...THE OWL CREEK/BRIDGER MTNS AND THE BIG HORN
MTNS IN THE FAVORABLE NORTHWEST FLOW...WITH THESE SNOW BANDS LIKELY
EXTENDING INTO THE LOWER ELEVATIONS OF EASTERN FREMONT...NATRONA AND
JOHNSON COUNTIES AS WELL AS GREATER CASPER. THE ECMWF IS SLOWER THAN
THE GFS WITH THIS TROUGH SO KEPT THE TIMING OF THE PRECIP THE SAME
WHICH IS A BLEND OF THE SPEED OF THE TWO MODELS. SNOWFALL WILL TAPER
OFF THURSDAY MORNING. EXPECT RATHER BENIGN CONDITIONS THU AFT
THROUGH FRIDAY WITH SLIGHTLY ABOVE NORMAL TEMPS. THEN ON SATURDAY
WILL KEEP THE LOW POPS IN THE FAR WEST WITH THE APPROACH OF THE NEXT
UPSTREAM TROUGH WITH THE EURO AGAIN FASTER THAN THE GFS SO WILL KEEP
THE TIMING OF THE ASCT PRECIP THE SAME WITH THE BLEND OF THE TWO
MODELS. TEMPS WILL WARM SOMEWHAT SATURDAY.

&&

.AVIATION.../06Z ISSUANCE/

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

VFR CONDITIONS WILL OCCUR TODAY AND TONIGHT. ISOLATED SHOWERS ARE
POSSIBLE ACROSS SOUTHERN NATRONA COUNTY FROM 21Z SUNDAY UNTIL 02Z
MONDAY. THE SHOWERS ARE NOT FORECAST TO HIT THE KCPR AIRPORT. A COLD
FRONT WILL PUSH THROUGH NORTHERN WY FROM 15Z TO 19Z AND PUSH SOUTH
INTO CENTRAL WY AROUND 00Z MONDAY. A WIND SHIFT TO THE NORTH WILL
BE THE MAIN IMPACT.

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

VFR CONDITIONS WILL OCCUR TODAY AND TONIGHT. ISOLATED SHOWERS WILL
BE POSSIBLE OVER THE NW WY MOUNTAINS UNTIL 18Z. ISOLATED SHOWERS AND
THUNDERSTORMS ARE POSSIBLE ACROSS SOUTHERN WY FROM 19Z SUNDAY UNTIL
02Z MONDAY. THIS ACTIVITY MAY IMPACT THE KRKS AIRPORT DURING THIS
TIMEFRAME.

&&

.FIRE WEATHER...

IT WILL BE MILD TO WARM AND DRY THE REMAINDER OF THE WEEKEND AND
IN MOST AREAS THROUGH MONDAY. THERE WILL BE BREEZY TO WINDY AREAS
AT TIMES AND A COLD FRONT WILL SHIFT WINDS TO THE NORTH ACROSS THE
NORTH AND EAST PART OF THE DISTRICT ON SUNDAY WHILE WEST TO
NORTHWEST WINDS CONTINUE ELSEWHERE. WINDS WILL STRENGTHEN
CONSIDERABLY MONDAY NIGHT AND TUESDAY AHEAD OF A SIGNIFICANT STORM
SYSTEM THAT WILL MOVE EAST ACROSS THE AREA TUESDAY THROUGH
WEDNESDAY. STRONG TO VERY STRONG SOUTHERLY WINDS ARE EXPECTED ON
TUESDAY WITH SHOWERS AND POSSIBLE THUNDERSTORMS DEVELOPING OUT
WEST AND ISOLATED SHOWERS AND THUNDERSTORMS EAST OF THE DIVIDE.

&&

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

&&

$$

SHORT TERM...SKRBAC
LONG TERM...LIPSON
AVIATION...AR
FIRE WEATHER...SKRBAC









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