Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 181700
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1100 AM MDT SAT OCT 18 2014

.SHORT TERM...SATURDAY THROUGH MONDAY NIGHT

THE WEATHER PATTERN FOR THE NEXT FEW DAYS CAN BE DESCRIBED IN A
SERIES OF THE LAST LETTER OF THE ALPHABET....ZZZZZZZZZZZZ. IN OTHER
WORDS...THINGS CONTINUE TO LOOK FAIRLY UNEVENTFUL THROUGH THE
WEEKEND. THE LONGWAVE PATTERN SHOWS AN UPPER LEVEL LOW AND TROUGH
DIGGING IN THE EASTERN UNITED STATES AND A TROUGH ACROSS THE WEST
COAST AS WELL. THIS MEANS A RIDGE PUMPING UP ACROSS THE CENTRAL
PLAINS AND MAINLY SOUTHWEST FLOW ACROSS WYOMING. THIS ALSO MEANS A
MILD AND MAINLY DRY PATTERN FOR THE NEXT FEW DAYS. A COUPLE OF
SHORTWAVES WILL MOVE THROUGH THE FLOW THE NEXT COUPLE OF DAYS BUT
WITH A DRY ATMOSPHERE THESE WILL ONLY BRING A FEW PERIODS OF
INCREASED MID TO HIGH LEVEL CLOUDS AT TIMES. THE ONE EXCEPTION MAY
BE EARLY THIS MORNING WITH A FEW SPRINKLES IN YELLOWSTONE WITH THE
FIRST SHORTWAVE BUT THAT WOULD BE IT. WITH THE SOUTHWEST
FLOW...EXPECT TEMPERATURES TO WARM ABOUT 5 TO 10 DEGREES WARMER
THAN ON FRIDAY. THESE MILD TEMPERATURES WILL CONTINUE THROUGH
SUNDAY WITH THE WARMEST DAY EXPECTED ON MONDAY. ONE SMALL WRINKLE
IS SHOWN ON THE NAM AS AN APPROACHING TROUGH TAPS INTO A LITTLE
MORE MOISTURE AND PRODUCES SOME SHOWERS ACROSS WESTERN WYOMING
LATE MONDAY NIGHT. THE GFS IS SLOWER AND HOLDS OFF PRECIPITATION
UNTIL TUESDAY. SINCE THIS IS THE FIRST TIME SHOWING THIS...WE WILL
MAINTAIN THE MAINLY DRY FORECAST THROUGH MONDAY NIGHT.


.LONG TERM...TUESDAY THROUGH SATURDAY

SYNOPSIS...A COLD FRONT WILL PUSH ACROSS THE AREA ON TUESDAY WITH A
CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW SHOWERS IN THE WEST...BREEZY
TO WINDY AND MILD CONDITIONS EAST OF THE DIVIDE.  COOLER CONDITIONS
WILL FOLLOW ON WEDNESDAY WITH SOME RAIN SHOWERS LINGERING ACROSS THE
SOUTH. A RIDGE OF HIGH PRESSURE WILL BRING DRY AND UNSEASONABLY MILD
CONDITIONS THURSDAY THROUGH NEXT WEEKEND.


DISCUSSION...UPPER TROUGH ACROSS THE EASTERN PACIFIC BETWEEN
160W-150W EARLY THIS MORNING IS FORECAST TO PUSH ONTO THE WEST COAST
LATE MONDAY AND SHEAR NE ACROSS NW WYOMING ON TUESDAY INTO
DOWNSTREAM RIDGE OVER THE PLAINS.  ASSOCIATED COLD FRONT IS FORECAST
TO PUSH INTO THE WEST TUESDAY MORNING AND ACROSS CENTRAL WYOMING
TUESDAY AFTERNOON.  H7 WESTERLY FLOW AT AROUND 30KTS WILL KEEP MOST
OF THE PRECIPITATION WITH THIS SYSTEM WEST OF THE DIVIDE WITH
DOWNSLOPE FLOW RESULTING IN MAINLY DRY...BREEZY/WINDY AND MILD
CONDITIONS EAST OF THE DIVIDE.  THE EXCEPTION WILL BE ACROSS THE FAR
NORTH OR VCNTY AND NORTH OF A KCOD-KBYG LINE WHERE STRONGER POSITIVE
VORTICITY ADVECTION WILL LIKELY RESULT IN SOME SHOWER ACTIVITY.

A TRAILING SHORTWAVE IS FORECAST TO PUSH EAST ACROSS THE GREAT BASIN
TUESDAY NIGHT AND ACROSS THE CENTRAL ROCKIES ON WEDNESDAY.  THE BEST
CHANCES OF SHOWERS WITH THIS SYSTEM WILL BE ALONG AND SOUTH OF
INTERSTATE 80 WEDNESDAY MORNING...WHILE DRIER AIR PUSHES INTO THE
NW.  THE "COOLER" TEMPERATURES BEHIND THE COLD FRONT ON WEDNESDAY
WILL STILL BE 5-8F ABOVE NORMAL FOR MOST AREAS.

THIS WILL BE FOLLOWED BY TEMPERATURES SOME 10-15F ABOVE AVERAGE
THURSDAY THROUGH SATURDAY AS A RIDGE OF HIGH PRESSURE SETS IN OVER
THE ROCKIES...FLANKED BY UPPER TROUGHS OFF THE COASTS.  THIS BLOCKY
PATTERN SHOULD HOLD THROUGH THE WEEKEND WITH MEDIUM-RANGE MODELS
TRENDING SLOWER WITH ANY PROGRESSION OF TROUGH OFF THE WEST COAST.
THUS...ANY CHANCES OF PRECIPITATION DO NOT ENTER THE PICTURE AGAIN
UNTIL MONDAY OCT 27TH OR LATER.

&&

.AVIATION.../18Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH 18Z SUNDAY. AN UPPER DISTURBANCE
WILL PRODUCE SCT/FEW MID TO HIGH LEVEL CLOUDS TODAY/TONIGHT WITH
CLEAR SKIES EVERYWHERE SUNDAY. OTHERWISE...LIGHT WIND AT 10KTS OR
LESS WILL BE COMMON FOR MOST TERMINALS AND SURROUNDING AREAS.

&&

.FIRE WEATHER...

MAINLY DRY AND TRANQUIL WEATHER WILL CONTINUE INTO THE WEEKEND AND
INTO MONDAY. A COUPLE OF UPPER LEVEL DISTURBANCES MOVING THROUGH
THE AREA WILL BRING SOME MID TO HIGH LEVEL CLOUDS AT TIMES ALONG
WITH OCCASIONAL BREEZY CONDITIONS. HOWEVER...FIRE DANGER IS
EXPECTED TO REMAIN RELATIVELY LOW.

&&

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

$$

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












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