Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 291005
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
405 AM MDT WED OCT 29 2014

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT...
PROGRESSIVE NW FLOW EARLY IN THE PERIOD WILL BECOME ANTICYCLONIC AS
A RIDGE AXIS AMPLIFIES ACROSS THE INTERMOUNTAIN WEST BY THE END OF
THE WEEK. THE PRIMARY FORECAST CHALLENGE CENTERS AROUND THE POTENTIAL
FOR A LOCALIZED HIGH WIND EVENT LATER TODAY. OTHERWISE...WEATHER
IMPACTS WILL BE MINIMAL THRU THE END OF THE WEEK.

A CLEAR START TO THE DAY AS MID/HIGH-LEVEL CLOUDS ASSOCIATED WITH
SHORTWAVE ENERGY SPILL SOUTHEAST INTO THE COWBOY STATE FROM MONTANA.
AT THE SFC...A WELL-DEFINED LEE SIDE SFC TROF HAS AMPLIFIED
SIGNIFICANTLY OVER THE PAST 6 HOURS OR SO. MODELS ARE CONSISTENT IN
SHIFTING THIS LEE SIDE PRESSURE TROF EAST TODAY. LLVL
HEIGHT/PRESSURE GRADIENTS WILL TIGHTEN AS A RESULT...WHICH WILL KICK
UP WINDS ACROSS MUCH OF SOUTHEAST WYOMING. MOST LOWER ELEVATIONS
WILL SEE BREEZY WINDS...WITH AFTERNOON GUSTS OF 25-35 MPH. THE
EXCEPTION WILL BE IN AND AROUND THE MOUNTAINS AND THRU THE WIND
CORRIDOR WHERE GUSTS OF 40-50 MPH WILL BE POSSIBLE. THE GFS IS THE
MOST AGGRESSIVE WITH WINDS PROGGING H7 WINDS OF AROUND 50 KNOTS OVR
THE SRN LARAMIE RANGE ALONG WITH A LARGE AREA OF SUBSIDENCE
BEHIND THE SHORTWAVE. THIS SEEMS TOO HIGH CONSIDERING THE OTHER
00Z DETERMINISTIC MODELS PEAK AT AROUND 40 KNOTS. AN EXAMINATION
OF THE H85/H7 KCAG-KCPR GRADIENTS SHOW 45-50 METERS WILL BE ABOUT
IT. THESE WILL PEAK AROUND MIDDAY. SO...WILL HOLD OFF ON ANY
HIGHLIGHT FOR NOW...EVEN THOUGH KARL AND KBRX MAY GET CLOSE. WILL
LIKELY SEE LEE WAVE CLOUD DEVELOPMENT NR THE FRONT RANGE TODAY AS
THE NOSE OF AN ANTICYCLONIC JET PASSES OVERHEAD. HIGHS WILL CLIMB
INTO THE 60S EAST OF THE LARAMIE RANGE...WITH 70S WEST.

SHORTWAVE ENERGY DEPARTS ON THURSDAY LEAVING NORTHWEST FLOW IN
PLACE. ALTHOUGH...HEIGHTS WILL BUILD LATE IN THE DAY AS UPSTREAM
RIDGING APPROACHES. WILL SEE A BIT OF BACK DOOR FRONT SNEAK IN TO
AREAS EAST OF THE LARAMIE RANGE ON THURSDAY...HOLDING HIGHS BACK TO
AROUND 60 MOST AREAS. THURSDAY WILL COMPRISE OF FAR LESS WIND
TOO...AT GENERALLY 5-10 MPH. THE RIDGE AXIS WILL BE FIRMLY IN
CONTROL FOR FRIDAY ALTHOUGH WINDS WILL INCREASE DURING THE AFTERNOON
HOURS AS THE NEXT LEE-SIDE PRESSURE TROUGH BEGINS TO DEVELOP. FRIDAY
LOOKS COOL AGAIN AS THE AIR MASS BEHIND THE BACK DOOR COLD FRONT IS
SLOW TO DEPART. HIGHS WILL ONLY REACH THE 50S.

.LONG TERM...(SATURDAY THROUGH TUESDAY)
ISSUED AT 345 AM MDT WED OCT 29 2014

LONG RANGE MODELS ARE STRUGGLING WITH THE OVERALL PATTERN AND IN
GENERALLY POOR AGREEMENT THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. THE MAIN FORECAST CHALLENGE IS SPLIT FLOW OVER THE AREA AS
PACIFIC STORM SYSTEMS INTERACT WITH THE RELATIVELY STRONG UPPER
LEVEL RIDGE OVER THE GREAT PLAINS. THE SOUTHERN BRANCH OF THE JET
WILL BECOME MORE ACTIVE INTO NEXT WEEKEND AS THE RIDGE OVER THE
PLAINS WILL SLOWLY WEAKEN...BUT STILL INFLUENCE. MODELS INDICATE
SOUTHEAST WYOMING AND WESTERN NEBRASKA IN THE MIDDLE OF THIS
TRANSITION. THE GFS AND ECMWF ARE IN RELATIVELY GOOD AGREEMENT
WITH REGARDS TO THE PACIFIC STORM SYSTEM PUSHING ONSHORE AND
GRADUALLY MOVING ACROSS THE GREAT BASIN REGION AND INTO THE ROCKY
MOUNTAINS BY SUNDAY. BOTH MODELS SHOW THE NORTHERN BRANCH A LITTLE
MORE ACTIVE AS THE SYSTEM TAKES MORE OF A NORTHWARD TRACK ACROSS
NORTHERN WYOMING AND MONTANA...WITH SOME RAIN/SNOW ACROSS THE
FORECAST AREA BUT GENERALLY LIGHT AMOUNTS. THE GEM AND A FEW
ENSEMBLE RUNS SHOW A MORE SOUTHERN TRACK...AS THE 500MB LOW PUSHES
NORTHEAST ACROSS EASTERN COLORADO. 00Z GEM SHOWS THE HIGHEST QPF
BY FAR AND IS CONSIDERED AN OUTLIER. INCREASED POP BETWEEN 15 TO
25 PERCENT FOR NOW...AND CLOSER TO 50 PERCENT ACROSS THE
MOUNTAINS. KEPT POP ON THE LOW SIDE DUE TO TIMING DIFFERENCES AND
CONSIDERABLE DISAGREEMENT IN EVOLUTION OF THE STORM AS IT MOVES
INTO THE PLAINS. HOWEVER...MODERATE TO HIGH CONFIDENCE THAT SOME
MUCH COOLER AIR WILL SPREAD ACROSS THE AREA FROM THE WEST WITH
HIGHS IN THE 40S EXPECTED BY SUNDAY AND MONDAY AFTER THE COLD
FRONT MOVES THROUGH THE AREA. GUSTY WINDS ARE EXPECTED BEGINNING
LATE SATURDAY NIGHT AND CONTINUING THROUGH SUNDAY AS THE FRONT
PUSHES THROUGH THE AREA. THERE IS THE POTENTIAL FOR HIGH WINDS
ACROSS THE WIND PRONE AREAS OF SOUTHEAST WYOMING BY SUNDAY
MORNING.

THE UPPER LEVEL TROUGH WILL PUSH EAST OF THE REGION EARLY NEXT
WEEK RESULTING IN BROAD NORTHWEST FLOW AND COOL TEMPERATURES. HIGH
TEMPERATURES WILL REMAIN SLIGHTLY BELOW NORMAL AND GENERALLY IN
THE 40S AND 50S WITH LOWS IN THE TEENS AND 20S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH TONIGHT)
ISSUED AT 300 AM MDT WED OCT 29 2014

LIGHT WINDS AND CLEAR SKIES ACROSS MOST OF THE AREA TONIGHT WITH
A RIDGE OF HIGH PRESSURE IN PLACE. INCREASING HIGH CLOUDS LATER
TODAY AS A SHORTWAVE MOVES EASTWARD ACROSS MONTANA. GUSTY WINDS
UP TO 35 KNOTS ARE EXPECTED THIS AFTERNOON WITH STRONG WEST WINDS
OVER HIGHER ELEVATIONS OF SOUTHEAST WYOMING.

&&

.FIRE WEATHER...HUMIDITY RECOVERIES HAVE BEEN POOR OVERNIGHT WITH
AREAS WEST OF I-25 ONLY DIPPING INTO THE 20-30 PERCENT RANGE. THIS
IS A PRECURSOR TO TODAY...AS THIS DRY AIR MASS COMBINES WITH
INCREASINGLY BREEZY TO LOCALLY WINDY CONDITIONS TO PRODUCE NEAR
CRITICAL CONDITIONS. THIS WILL ESPECIALLY BE THE CASE FOR FIRE
WEATHER ZONE 310...WHERE CONDITIONS WILL BE THE DRIEST LATER TODAY.
FUELS ARE NON-CRITICAL IN THESE AREAS...SO NO NEED FOR A FIRE
WEATHER HIGHLIGHT. OTHERWISE...EXPECT A DRY AND BREEZY TO LOCALLY
WINDY TODAY WITH HIGHS RISING INTO THE 60S EAST OF THE LARAMIE
RANGE...AND 50S WEST. DRY CONDITIONS WILL CONTINUE ON
THURSDAY...WITH MUCH LESS WIND EXPECTED. A BACK DOOR COLD FRONT WILL
USHER IN SLIGHTLY COOLER TEMPERATURES OVER THE EASTERN PLAINS
THURSDAY AND FRIDAY. THE NEXT SYSTEM WILL BEGIN TO IMPACT THE AREA
LATE IN THE WEEKEND.

&&

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

$$

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



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