Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 181636
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1036 AM MDT FRI APR 18 2014

.UPDATE...
ISSUED AT 1016 AM MDT FRI APR 18 2014

CLOUD COVER BECOMING THICKER A BIT FASTER THAN ANTICIPATED THIS
MORNING...OTHERWISE FORECAST MOSTLY IN GOOD SHAPE. WITH THE
THICKER CLOUDS...SHAVED A FEW DEGREES OFF A FEW SITES BUT WITH
WESTERLY WINDS AND DRY AIR ALOFT...PREVIOUS FORECAST SHOULD BE
CLOSE. CAN NOT RULE OUT SOME CONVECTION THIS AFTERNOON WITH STEEP
LAPSE RATES IN PLACE...BUT GENERAL LACK OF MOISTURE AND HIGH
CLOUDS MAY INHIBIT ANY CONVECTION OUTSIDE OF THE MOUNTAINS UNTIL
THE MAIN TROUGH MOVES IN THIS EVENING.


&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 349 AM MDT FRI APR 18 2014

FORECAST CHALLENGES DEAL WITH TEMPERATURES TODAY FOLLOWED BY
SHOWER CHANCES THIS WEEKEND.

CURRENTLY...SURFACE LOW PRESSURE CURRENTLY OVER SOUTHERN IDAHO
WITH A 1017MB SURFACE HIGH OVER NORTH CENTRAL COLORADO. WINDS HAVE
STAYED UP SO FAR...WHICH IS KEEPING TEMPERATURES PRETTY WARM.
SEEING 1 AM TEMPERATURES IN THE UPPER 30S AND LOW 40S FOR MANY
LOCATIONS.

FOR TODAY...SURFACE LOW TRACKS ACROSS SOUTHERN MONTANA AND
NORTHERN WYOMING THROUGH THE DAY. GFS 700MB WINDS PICK UP TO
40KTS...SO LOOKS LIKE WE ARE IN FOR A RATHER WINDY DAY. GFS 700MB
TEMPERATURES ALSO CLIMB TO +8C. STILL THINK MOS GUIDANCE IS LOW ON
FORECAST HIGHS TODAY WITH THESE STRONG DOWNSLOPING WINDS. ADDED
3-4 DEGREES TO THE MOS GUIDANCE FOR HIGHS. LOOKING AT PROBABLY THE
WARMEST DAY THIS SEASON SO FAR WITH 80S COMMON IN THE PANHANDLE
AND 70S ACROSS SOUTHEAST WYOMING.

ONE FINAL ITEM FOR TODAY AND TONIGHT WOULD BE THUNDERSTORM CHANCES
WITH THE FRONT. NAM LIFTED INDICES OF -2 TO -3C LATE THIS
AFTERNOON AND EARLY EVENING. NAM AND GFS PAINTING SOME LIGHT QPF
OVER CONVERSE AND NIOBRARA COUNTIES AND EVEN THE NORTHERN
PANHANDLE UP NEAR CHADRON. WENT AHEAD AND UPPED POPS TO CHANCE
CATEGORY FOR EARLY THIS EVENING.

FRONT LOOKS TO MOVE THROUGH EARLY SATURDAY MORNING WITH WINDS
SHIFTING EASTERLY. GFS SHOWING SOME POOLING OF LOW LEVEL MOISTURE
OVER WESTERN NEBRASKA WITH THESE EASTERLY WINDS WITH 850MB RH
AROUND 95 PERCENT JUST EAST OF OUR CWFA. WILL NEED TO WATCH WHERE
THIS LOW LEVEL FINALLY ENDS UP PULLING...WOULD THINK IT WOULD MAKE
IT INTO THE PANHANDLE WITH THOSE TYPE OF WINDS. WILL CONTINUE TO MONITOR.

MODELS HITTING OUR WESTERN ZONES PRETTY GOOD SATURDAY AFTERNOON
AND EVENING WITH DECENT RAINFALL. A FAIRLY POTENT SHORTWAVE TRACKS
ACROSS NORTHERN COLORADO SATURDAY AFTERNOON...THEN INTO CENTRAL
NEBRASKA SATURDAY EVENING. ALL THREE MODELS ARE IN GOOD AGREEMENT
WITH LOCATIONS. THE NAM MOST BULLISH ON QPF WITH CLOSE TO 4/10THS
QPF NEAR LARAMIE. UPPED POPS A LITTLE MORE WITH THIS GOOD
AGREEMENT IN GUIDANCE.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)

ISSUED AT 349 AM MDT FRI APR 18 2014

MODELS ARE FAIRLY SIMILAR WITH THE SYNOPTIC PATTERN THRU THE EARLY
PART OF THE WEEK...BUT THEN DIVERGE QUITE A BIT FOR WEDNESDAY AND
BEYOND. A SHORTWAVE RIDGE WILL MOVE OVERHEAD MONDAY AND MONDAY NIGHT
WITH SFC HIGH PRESSURE MOVING EAST ACROSS THE REGION. TEMPS WILL BE
SLIGHTLY COOLER WITH THE THERMAL RIDGE AND THUS WARMEST TEMPS
LAGGING JUST WEST OF THE MAIN RIDGE AXIS...WITH SOUTHEASTERLY SFC
FLOW ADVECTING LLVL MOISTURE UP ALONG THE LARAMIE RANGE. COULD SEE A
TSTORM OR TWO DEVELOP MONDAY AFTERNOON ALONG THE LARAMIE RANGE AS A
RESULT...BUT CHANCES ARE LOW. A STRONG UPPER TROUGH WILL MOVE
ONSHORE INTO CALI MONDAY NIGHT AND WILL MOVE ACROSS THE GREAT BASIN
TUESDAY. UPPER LEVEL ENERGY EJECTING OUT AHEAD OF THE TROUGH IN
SOUTHWEST FLOW WILL BRING A SLIGHT CHANCE FOR OROGRAPHIC STORMS
AGAIN TUESDAY AFTERNOON...WITH THE MORE AGGRESSIVE GFS ALSO
DEVELOPING STRONGER CONVECTION ACROSS THE NEBRASKA PLAINS TUESDAY
EVENING. WILL KEEP A SLIGHT CHANCE FOR TSTORMS IN THESE AREAS
THROUGH TUESDAY EVENING TO ACCOUNT FOR MODEL DIFFERENCES...AS THE
ECMWF IS SHOWING LESS ENERGY MOVING OVERHEAD IN ADDITION TO MARGINAL
MOISTURE. THE GFS THEN DEVELOPS A CLOSED LOW TUESDAY NIGHT WHILE THE
ECMWF KEEPS AN OPEN WAVE TROUGH. THE CANADIAN MODEL LOOKS TO BE
SOMEWHERE IN THE MIDDLE. FOR WEDNESDAY...LOOKING AT CONTINUED LOW
CHANCES FOR RAIN...WITH THE BIGGER ISSUE LOOKING TO BE WINDY
CONDITIONS DEVELOPING BEHIND THE PACIFIC FRONT THAT IS PROGGED TO
MOVE THROUGH THE CWA WEDNESDAY MORNING. THE MORE PROGRESSIVE EC
TROUGH WILL THEN MOVE INTO THE CENTRAL PLAINS AND MIDWEST WEDNESDAY
NIGHT THROUGH THURSDAY NIGHT WHILE THE GFS MAINTAINS A STRONG STORM
SYSTEM OVER THE ROCKIES AND CENTRAL PLAINS. WILL KEEP A SLIGHT
CHANCE FOR RAIN AND NIGHTTIME SNOW SHOWERS MAINLY IN THE MOUNTAINS
AND NORTHERN ZONES BUT OVERALL CONFIDENCE IS LOW DUE TO THESE
SIGNIFICANT MODEL DIFFERENCES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 558 AM MDT FRI APR 18 2014

VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. THERE IS A SLIGHT
CHANCE FOR TSTORMS THIS EVENING MAINLY AT KCDR AS A COLD FRONT
BEGINS TO DROP SOUTH THROUGH THE REGION. OTHERWISE...THE MAIN
ISSUE WILL BE GUSTY SOUTHWEST WINDS DEVELOPING LATE THIS MORNING
AND CONTINUING THROUGH THIS EVENING UNTIL COLD FRONTAL PASSAGE.
GUSTS OF 25 TO 40 KTS ARE EXPECTED AT ALL TERMINALS...WITH THE
HIGHEST WINDS AT KRWL. THE COLD WILL STEADILY MOVE FROM NORTH TO
SOUTH ACROSS THE EASTERN PLAINS BETWEEN 05 AND 10Z TONIGHT.


&&

.FIRE WEATHER...
ISSUED AT 349 AM MDT FRI APR 18 2014

ELEVATED FIRE WEATHER CONCERNS TODAY AS A LOW PRESSURE AREA MOVES
THROUGH MONTANA. WINDS REALLY BEGIN TO PICK UP TOWARDS NOON TIME
TODAY AHEAD OF THE LOW PRESSURE SYSTEM. WITH TEMPERATURES IN THE
70S ACROSS SOUTHEAST WYOMING AND 80S IN THE PANHANDLE...AFTERNOON
HUMIDITIES WILL FALL INTO THE MID TO UPPER TEENS TODAY. FRONT
ASSOCIATED WITH THE LOW PRESSURE MOVES INTO SOUTHEAST WYOMING LATE
TONIGHT...WITH WINDS SHIFTING TO THE NORTHEAST AND TEMPERATURES
COOLING DOWN SOME. INCREASING CHANCES FOR WETTING RAINS AND
MOUNTAIN SNOW SATURDAY NIGHT INTO SUNDAY FOR AREAS ALONG AND WEST
OF THE LARAMIE RANGE AS LOW PRESSURE TRACKS ACROSS NORTHERN
COLORADO.

&&

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

$$

UPDATE...SML
SHORT TERM...CLAYCOMB
LONG TERM...RJM
AVIATION...RJM
FIRE WEATHER...CLAYCOMB






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