Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 010440
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1040 PM MDT THU APR 30 2015

UPDATED FOR 06Z AVIATION DISCUSSION.

.SHORT TERM...TONIGHT THROUGH FRIDAY (ISSUED AT 216 PM MDT)

A COLD FRONT HAS MOVED SOUTH THROUGH THE NORTHERN THREE QUARTERS OF
WYOMING AND WILL PUSH ON SOUTH INTO NORTHERN COLORADO BY 06Z.
AN UPPER LEVEL LOW PRESSURE TROUGH HAS MOVED THROUGH THE NORTHWEST
CORNER OF WYOMING AND WILL SWEEP SOUTH AND EAST THROUGH THE STATE
THROUGH 06Z. AHEAD OF THE UPPER LEVEL TROUGH...ALONG AND WITHIN 60
MILES NORTH OF THE COLD FRONT...SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS WITH SMALL HAIL AND STRONG GUSTY WINDS UP TO 45KTS
WILL BE A THREAT THROUGH 06Z. AFTER 06Z A FEW SHOWERS WILL LINGER
OVER THE EAST AND SOUTH BEFORE DISSIPATING.  CLEARING WILL THEN
CONTINUE THROUGH FRIDAY. A FEW SHOWERS AND THUNDERSTORMS MAY BRUSH
THE SOUTHERN THIRD OF SWEETWATER COUNTY FRIDAY AFTERNOON.
TEMPERATURES WILL COOL BEHIND THE COLD FRONT WITH THE COLDEST
TEMPERATURES AROUND SUNRISE FRIDAY MORNING. MOST MOUNTAIN AREAS WILL
SEE FREEZING TEMPERATURES ALONG WITH THE WESTERN VALLEYS.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY

ZONAL FLOW OVER THE AREA BEGINS THE FORECAST PERIOD..WITH GENERALLY
DRY AND WARM CONDITIONS ACROSS THE FORECAST AREA. THESE BENIGN
CONDITIONS WANE SATURDAY AFTERNOON AND EVENING AS A PUSH OF MOISTURE
MOVES ACROSS WESTERN WYOMING. THIS MOISTURE SURGE WILL GENERALLY
BRING SHOWERS ACROSS SOUTHERN AND WESTERN WYOMING...THOUGH A FEW
SHOWERS MAY MOVE EAST OF THE CONTINENTAL DIVIDE DURING THE OVERNIGHT
HOURS. TEMPERATURES WILL ALSO START A GENERAL COOLING TREND...THOUGH
WILL STILL BE SEASONALLY MILD.

THE PERIODIC PUSHES OF MOISTURE CONTINUE SUNDAY AFTERNOON AND
EVENING. COVERAGE INCREASES WITH THE PUSH...WITH SHOWERS BEGINNING
OVER MUCH OF THE FORECAST AREA. SHOWER COVERAGE INCREASES EACH
AFTERNOON WITH THE CONTINUED PUSHES OF MOISTURE...WITH SHOWERS AND
THUNDERSTORMS CONTINUING INTO THE EVENING AND OVERNIGHT HOURS.

THIS PATTERN WILL CONTINUE THROUGH THURSDAY ACROSS THE AREA. AN
APPROACHING AREA OF LOW PRESSURE MAY FURTHER INCREASE COVERAGE OF
SHOWER ACTIVITY WEDNESDAY AND INTO THURSDAY...THOUGH MODELS VARY ON
THE PLACEMENT AND STRENGTH OF THE AREA OF LOW PRESSURE. THE AREA OF
LOW PRESSURE CONTINUES TO MOVE TOWARDS WYOMING ON THURSDAY...WITH
SHOWERS CONTINUING ALONG WITH COOLING TEMPERATURES.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL OVERNIGHT AND THROUGH FRIDAY NIGHT.
ISOLATED SHOWERS OR STORMS WILL OCCUR ALONG THE FAR SOUTH BORDER
WITH UTAH AND COLORADO FROM 21Z FRIDAY THROUGH 06Z SATURDAY.

&&

.FIRE WEATHER...

A COLD FRONT HAS MOVED SOUTH THROUGH THE NORTHERN THREE QUARTERS OF
WYOMING AND WILL PUSH ON SOUTH INTO NORTHERN COLORADO BY 06Z.
AN UPPER LEVEL LOW PRESSURE TROUGH HAS MOVED THROUGH THE NORTHWEST
CORNER OF WYOMING AND WILL SWEEP SOUTH AND EAST THROUGH THE STATE
THROUGH 06Z. AHEAD OF THE UPPER LEVEL TROUGH...ALONG AND WITHIN 60
MILES NORTH OF THE COLD FRONT...SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS WITH SMALL HAIL AND STRONG GUSTY WINDS UP TO 45KTS
WILL BE A THREAT THROUGH 06Z. AFTER 06Z A FEW SHOWERS WILL LINGER
OVER THE EAST AND SOUTH BEFORE DISSIPATING.  CLEARING WILL THEN
CONTINUE THROUGH FRIDAY. A FEW SHOWERS AND THUNDERSTORMS MAY BRUSH
THE SOUTHERN THIRD OF SWEETWATER COUNTY FRIDAY AFTERNOON.
TEMPERATURES WILL COOL BEHIND THE COLD FRONT WITH THE COLDEST
TEMPERATURES AROUND SUNRISE FRIDAY MORNING. MOST MOUNTAIN AREAS WILL
SEE FREEZING TEMPERATURES ALONG WITH THE WESTERN VALLEYS.  FAVORABLE
RELATIVE HUMIDITY IS EXPECTED THROUGH THE MORNING...THEN RATHER LOW
RELATIVE HUMIDITY IS EXPECTED FRIDAY AFTERNOON. MIXING HEIGHTS WILL
REBOUND DURING THE DAY WITH GENERALLY GOOD OR BETTER SMOKE DISPERSAL
FRIDAY AFTERNOON.

&&

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

&&

$$

SHORT TERM...C.BAKER
LONG TERM...BRANHAM
AVIATION...AR
FIRE WEATHER...C.BAKER










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