Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 302210
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
310 PM MST FRI JAN 30 2015

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 250 PM MST FRI JAN 30 2015

MODELS IN GOOD AGREEMENT THROUGH THIS WEEKEND SHOWING THE OVERALL
WEATHER PATTERN TRANSITIONING TOWARDS NORTH TO NORTHWEST FLOW AND
COLDER TEMPERATURES. CURRENT WATERVAPOR SATELLITE LOOP SHOWS THE
BROAD UPPER LEVEL LOW...WHICH IS RESPONSIBLE FOR BREAKING DOWN THE
STRONG UPPER LEVEL RIDGE ALONG THE WEST COAST EARLIER THIS
WEEK...OVER SOUTHERN CALIFORNIA THIS AFTERNOON. THIS LOW WILL
INITIALLY DRIFT EASTWARD TONIGHT...HOWEVER...SATELLITE IMAGERY
SHOWS A SHORTWAVE MOVING ACROSS BRITISH COLUMBIA AND DIGGING
SOUTHEAST INTO MONTANA LATE TONIGHT AND INTO EARLY SATURDAY. THIS
FEATURE WILL BE ASSOCIATED WITH A COLD FRONT WITH A MODIFIED
ARCTIC AIRMASS PUSHING INTO THE NORTHERN PLAINS. THIS WILL RESULT
IN THE BROAD UPPER LEVEL LOW OVER THE DESERT SOUTHWEST TO BEGIN
DIGGING SOUTH AND SOUTHEAST INTO MEXICO ON SATURDAY...MAINLY
MISSING MOST OF SOUTHEAST WYOMING AND WESTERN NEBRASKA. CAN NOT
RULE OUT SOME LIGHT SNOW ALONG AND SOUTH OF I80 HOWEVER...SO KEPT
POP BETWEEN 15 TO 30 PERCENT FROM RAWLINS TO CHEYENNE TONIGHT AND
EARLY SATURDAY. THE HIGH PLAINS MAY GET CLIPPED BY THE REAR
ENTRANCE REGION OF A STRENGTHENING JET ALOFT...BUT PRECIPITATION
WILL LIKELY BE MIXED WITH RAIN DURING THE DAY. REMOVED THE
POTENTIAL FOR FOG TONIGHT AND EARLY SATURDAY SINCE THE UPPER LEVEL
LOW WILL BE TOO FAR SOUTH AND LLVL WINDS WILL BE LIGHT NORTHERLY.
THE BEST CHANCE FOR SOME LOWER VISIBILITIES WILL BE THE CHEYENNE
RIDGE FROM KIMBALL TO SIDNEY...AND MAYBE THE LOWER ELEVATIONS OF
CARBON COUNTY IF WINDS BECOME LIGHT FOR A TIME BEFORE SHIFTING
INTO THE NORTHEAST. IN ADDITION...MID TO HIGH CLOUDS WILL BE
PROBLEMATIC FOR LLVL FOG DEVELOPMENT...SO MAY JUST SEE LOW CLOUDS
ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. KEPT LOW
TEMPERATURES ABOVE MODEL GUIDANCE DUE TO THIS CLOUD COVER.
TEMPERATURES WILL BE NEAR NORMAL FOR SATURDAY...WITH HIGHS IN THE
UPPER 30S TO MID 40S. WITH THE EXCEPTION OF THE EXITING JET
ALOFT...WEATHER SHOULD BE RELATIVELY DRY OUTSIDE THE MOUNTAINS
WITH MINIMAL SNOW ACCUMULATIONS.

BY SATURDAY NIGHT THROUGH SUNDAY NIGHT...THE COLD FRONT PUSHES
ACROSS THE AREA WITH THE COLDEST AIR ACROSS THE HIGH PLAINS. THIS
MAY BE THE BEST CHANCE FOR MOST AREAS TO SEE A LITTLE BIT OF LIGHT
SNOW ACCORDING TO THE SHORT TERM ENSEMBLES. INCREASED POP BETWEEN
20 TO 35 PERCENT ACROSS MOST OF THE AREA...ESPECIALLY ALONG AND
EAST OF THE LARAMIE RANGE. TEMPERATURES WILL BE BELOW NORMAL ON
SUNDAY BUT DRIER AIR WILL PUSH INTO THE AREA DURING THE AFTERNOON
AS THE TROUGH QUICKLY DIGS SOUTHEAST ACROSS THE CENTRAL PLAINS.
MODELS SHOW THE POTENTIAL FOR STRONG WINDS ACROSS SOUTHEAST
WYOMING BY LATE SUNDAY NIGHT AS A LLVL GRADIENT INCREASES ALONG
THE LARAMIE RANGE.

.LONG TERM...(MONDAY THROUGH NEXT FRIDAY)
ISSUED AT 250 PM MST FRI JAN 30 2015

MONDAY WILL START OUT BREEZY WITH WINDS ACROSS THE NORMALLY WINDIER
LOCATIONS ALONG AND WEST OF THE LARAMIE RANGE GUSTING 35 TO 45 MPH
OUT OF THE WEST IN THE MORNING AS A SHORTWAVE MOVES SOUTHEAST ACROSS
WYOMING.  THE SHORTWAVE MOVES QUICKLY OUT TO THE EAST BY MONDAY
AFTERNOON...BUT WITH THE MID/UPPER FLOW PERSISTING OUT OF THE
NORTHWEST SHOULD SEE ADDITIONAL WEAK SHORTWAVES MOVE DOWN ACROSS THE
AREA TUESDAY THROUGH THURSDAY.  WE MAY GET A PERIOD AGAIN TUESDAY
WITH SLIGHTLY INCREASED WINDS GUSTING 30-40 MPH.  KEPT CHANCES OF
SNOW GOING IN THE HIGHER TERRAIN ACROSS PORTIONS OF CARBON...ALBANY
AND WESTERN LARAMIE COUNTIES MONDAY INTO TUESDAY...BUT SNOWFALL
TOTALS SHOULD REMAIN FAIRLY LIGHT.  BY TUESDAY NIGHT...A FAIRLY
ROBUST UPPER DISTURBANCE WILL CARVE OUT AN UPPER TROUGH OVER THE
DAKOTAS AND MINNESOTA...GIVING THE ARCTIC AIRMASS LOCKED TO OUR
NORTH A QUICK SHOVE SOUTHWARD BY WEDNESDAY MORNING.  THE COLD FRONT
ON THE WESTERN EDGE OF THAT AIRMASS WILL MOVE INTO THE EASTERN HALF
OF OUR FORECAST AREA TUESDAY NIGHT BEFORE HANGING UP IN THE
MOUNTAINS.  SOME OF THE GUIDANCE CAME UP ON LOW TEMPERATURES
WEDNESDAY MORNING CONTRARY TO THE PHYSICAL GUIDANCE OF THE GFS AND
ECMWF WHICH SHOWS SHALLOW COLDER AIRMASS WORKING IN FROM THE
NORTHEAST.  FOR THIS PACKAGE WE OPTED TO STAY CLOSER TO OUR PREVIOUS
MIDNIGHT SHIFT FORECAST UNTIL GUIDANCE TRENDS BECOME MORE
CONSISTENT...KEEPING LOWS IN THE TEENS EAST OF THE LARAMIE RANGE
WEDNESDAY AND THURSDAY MORNINGS. WE ALSO KEPT SLIGHT CHANCE TO
CHANCE POPS FOR SHOWERS (SNOW WEST AND A MIX EAST) GOING ACROSS THE
AREA ON WEDNESDAY IN ASSOCIATION WITH THE SURFACE BOUNDARY AND A
PASSING UPPER DISTURBANCE.   LOOKING FARTHER OUT...UPPER RIDGING
WILL WORK IN FROM THE WEST THURSDAY INTO FRIDAY.  WE SHOULD SEE
DECREASED POPS AND A BIT OF A WARMUP LATE THURSDAY INTO FRIDAY WITH
TEMPERATURES OUT WEST ON FRIDAY IN THE 40S (EXCEPT 30S IN THE
MOUNTAINS) AND 50S OUT EAST ON THE PLAINS.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1114 AM MST FRI JAN 30 2015

CURRENTLY GETTING MVFR CATEGORY OBSERVED AT RAWLINS WY WHERE LIGHT
SNOW SHOWERS ARE PRODUCING VISIBILITIES DOWN TO 2SM...BUT THAT
SHOULD NOT BE A PREVAILING CONDITION THROUGH THE AFTERNOON WITH MVFR
CEILINGS BKN 2000FT AGL EXPECTED. OTHERWISE REST OF FORECAST AREA
EXPECTED TO SEE VFR CONDITIONS THROUGH THE EVENING WITH LOWERING
CEILINGS TO MVFR ACROSS THE ALLIANCE AND SIDNEY NE AREAS LATER
TONIGHT WITH LIGHT SOUTHERLY FLOW. MAY GET SOME PATCHY FOG IN SPOTS
TONIGHT (PARTICULARLY WHERE ANY LIGHT UPSLOW DEVELOPS). WILL ALSO
SEE A CHANCE OF LIGHT SNOW WITH MVFR CATEGORY CONDITIONS POSSIBLE
RAWLINS AND LARAMIE CLOSER TO WHERE ORAGRAPHICALLY INDUCED SNOW
SHOWERS IN THE MOUNTAINS ARE EXPECTED...BUT OTHERWISE NO MAJOR
CONCERNS THROUGH TOMORROW MORNING AND WE DONT EXPECT TO SEE
PREVAILING REDUCED VISIBILITIES DUE TO SNOW FOR THOSE LOCATIONS
THROUGH MORNING. THE HIGHER SNOW CHANCES THROUGH MORNING ARE
EXPECTED TO BE TO OUR SOUTH IN THE COLORADO MOUNTAINS.

&&

.FIRE WEATHER...
ISSUED AT 150 PM MST FRI JAN 30 2015

NO FIRE WEATHER CONCERNS ANTICIPATED. RECENT MILD SPRING-LIKE
CONDITIONS WILL END BY THIS WEEKEND AS AN ARCTIC COLD FRONT MOVES
SOUTHWARD ACROSS THE AREA BY SATURDAY. COOL TEMPERATURES...HIGH
RELATIVE HUMIDITIES...AND A CHANCE OF LIGHT PRECIPITATION ARE
EXPECTED INTO EARLY NEXT WEEK. ANOTHER STRONG COLD FRONT MAY
IMPACT THE REGION ON WEDNESDAY...BRINGING WIDESPREAD SNOWFALL TO
SOUTHEAST WYOMING AND PORTIONS OF WESTERN NEBRASKA.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&

$$

SHORT TERM...TJT
LONG TERM...JG
AVIATION...JG
FIRE WEATHER...TJT



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