Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 161756
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1056 AM MST SUN NOV 16 2014

.UPDATE...
ISSUED AT 646 AM MST SUN NOV 16 2014

WINDS HAVE INCREASED IN THE ARLINGTON AND BORDEAUX AREAS THIS
MORNING IN RESPONSE TO STRENGTHENING LLVL GRADIENTS ASSOCIATED
WITH SFC TROUGH TRANSLATING ACROSS THE NORTHERN PLAINS. CAG-CPR
GRADIENT AT H85 PEAKS AT 50 METERS BY 18Z. THIS IS MARGINAL FOR
WARNING CRITERIA WINDS...BUT THINK RELATIVELY MODEST FLOW ALOFT
WITH ONLY AROUND 40 KTS AVAILABLE TO MIX WILL KEEP GUSTS BELOW 50
MPH. UPDATED GRIDS TO REFLECT THE EARLY RAMP-UP IN WINDS AS WELL
AS BLOWING SNOW POTENTIAL IN THE WIND CORRIDORS.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY NIGHT)
ISSUED AT 256 AM MST SUN NOV 16 2014

A COLD START TO THE DAY WITH WIND CHILL READINGS IN THE -20 TO -30F
RANGE ACROSS MUCH OF THE CWA AS OF 09Z. LATEST SFC ANALYSIS SHOWS A
1040 MB ARCTIC HIGH CENTERED OVER THE INTERMOUNTAIN WEST...KEEPING
SKIES CLEAR BENEATH LARGE SCALE SUBSIDENCE. PRESSURE GRADIENTS ARE
STRONG ENOUGH TO KEEP WINDS IN THE 8 TO 12 MPH RANGE...SO THE WIND
CHILL HEADLINES WILL CONTINUE THROUGH 15Z. AS EXPECTED...GUSTY WEST
WINDS EAST OF THE LARAMIE RANGE ARE KEEPING THINGS WELL MIXED OVER
LARAMIE COUNTY. THE TEMPERATURE AT CHEYENNE HAS RISEN TO 7 DEGREES
FROM AROUND 0 AT 10 PM...SO NO WIND CHILL CONCERNS HERE. WATER VAPOR
SATELLITE LOOP SHOWS A RATHER POTENT MIDLVL SHORTWAVE DIVING SOUTH
ACROSS SOUTHERN SASKATCHEWAN. GFS AND NAM ARE IN GOOD AGREEMENT WITH
A BELT OF STRONGER 750-850 MILLIBAR FLOW AROUND 45 KTS ACROSS EAST
CENTRAL WY AND THE NORTHERN PANHANDLE AS THE WAVE TRACKS ACROSS THE
WESTERN DAKOTAS. BUFKIT SOUNDINGS SUGGEST SUFFICIENT LLVL MIXING TO
BRING STRONGER WINDS ALOFT DOWN TO THE SFC WITH UNIDIRECTIONAL FLOW
THROUGH THE COLUMN. COMBINATION OF 4-6 INCHES OF NEW SNOW AND WINDS
GUSTING TO 40 MPH WILL CAUSE BLOWING SNOW CONCERNS FOR THE NORTHERN
TIER OF COUNTIES FROM LATE AM THROUGH EARLY EVE. WILL ISSUE A WINTER
WEATHER ADVISORY FOR BLOWING SNOW PER COLLABORATION WITH
NEIGHBORING WFOS. AT LEAST SPORADIC WIND GUSTS TO 40 MPH SEEM
PROBABLE OVER MUCH OF THE PANHANDLE TODAY. HOWEVER...DO NOT EXPECT
IT TO BE PERSISTENT AS HIGH CLOUDS WILL INCREASE FROM THE NORTH.
MOS GUIDANCE IS PRETTY MARGINAL FOR WIND ADVISORY TOO SO WILL HOLD
OFF ON THAT HEADLINE FOR NOW WHERE BLOWING SNOW SHOULD NOT BE A
PROBLEM.

PVA ASSOCIATED WITH THE WAVE AND INSTABILITY BENEATH CYCLONIC MIDLVL
FLOW SHOULD PROMOTE ISOLATED LIGHT SNOW SHOWERS OVER OUR NORTHEAST
ZONES THIS AFTN AND TONIGHT. MEASURABLE PCPN COULD BE HARD TO COME
BY...BUT WILL MAINTAIN SLIGHT CHANCE POPS. VISIBILITY WILL LIKELY BE
LOCALLY REDUCED WITH THE ADDED SNOW AND WIND. NOT MUCH HAS CHANGED
FROM THE PREVIOUS FORECAST THINKING. STILL EXPECT WESTERLY DOWNSLOPE
FLOW TO CONTRIBUTE TO GOOD WARMING EAST OF THE LARAMIE RANGE BEFORE
LLVL COLD ADVECTION KICKS IN BEHIND THE NEXT FRONT. WILL BE HARD TO
GET ABOVE FREEZING WITH H7 TEMPS AROUND -14C...BUT SHOULD BE CLOSE
TO 30 DEGREES TODAY. COOLER UP NORTH WHERE SNOWPACK WILL LIMIT SFC
INSOLATION. EXPECT LITTLE CHANGE IN TEMPERATURES ON MONDAY WITH THE
REINFORCING SHOT OF COOL AIR. GFS/NAM/ECMWF ALL SUGGEST VERY STRONG
NORTHWEST FLOW ALOFT WILL REMAIN IN PLACE OVER THE CWA INTO TUE. WE
MAY BE LOOKING AT ANOTHER HIGH WIND EVENT FOR THE WIND PRONE AREAS
AS THE 850 MILLIBAR CAG-CPR GRADIENT IS PROGGED TO BE NEAR 60 METERS
BY MIDDAY IN THE RIGHT EXIT REGION OF A 130 KT JET OVER EASTERN MT.
TUE WILL BE THE WARMEST DAY OF THE PERIOD AS MODELS SHOW 700 MB TEMPS
APPROACHING 0C OVER THE PLAINS.

.LONG TERM...(WEDNESDAY THROUGH SATURDAY)
ISSUED AT 256 AM MST SUN NOV 16 2014

TEMPERATURES RETURNING TO NEAR NORMAL IN THE LONG TERM AS WE STAY
IN NORTHWEST FLOW. MAINLY DRY WITH WESTERLY DOWNSLOPING WINDS.
AFTERNOON HIGHS GETTING BACK INTO THE UPPER 30S AND LOW 40S BY
THURSDAY EAST OF THE LARAMIE RANGE.

SOME DIFFERENCES IN PRECIP CHANCES TOWARDS THE END OF THE EXTENDED
PERIOD. THE LATEST ECMWF CONTINUES TO SHOW A SHORTWAVE MOVING INTO
WESTERN WYOMING LATE SATURDAY WITH SNOW SHOWERS MOVING INTO CARBON
COUNTY AND THE MOUNTAINS SATURDAY INTO SUNDAY. GFS DRIVES THIS
SHORTWAVE SOUTH INTO SOUTHERN COLORADO...THOUGH IT DOES SHOW SOME
LIGHT QPF OVER THE SNOWY AND SIERRA MADRE RANGES. WENT AHEAD AND
KEPT CHANCE TO HIGH END CHANCE POPS IN FOR THE MOUNTAINS OF CARBON
COUNTY FOR SATURDAY AFTERNOON AND EVENING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1049 AM MST SUN NOV 16 2014

ANOTHER FAST MOVING PIECE OF UPPER LEVEL ENERGY WILL DIVE OUT OF
WESTERN SOUTH DAKOTA AND ACROSS THE WESTERN NEBRASKA PANHANDLE
THIS AFTERNOON. MVFR CEILINGS LIKELY ACROSS MUCH OF THE PANHANDLE
LATER TODAY AND THROUGH MUCH OF TONIGHT. COULD ALSO SEE REDUCED
VISIBILITIES SHOULD ANY SNOW FALL DURING THE PASSAGE OF THE UPPER
LEVEL ENERGY. MAIN CHANCE FOR SOME SNOW THIS AFTERNOON IS NEAR
CHADRON NEBRASKA...OTHERWISE NOT MUCH MORE THAN A FEW SNOW
FLURRIES.

WINDS WILL BE GUSTY ESPECIALLY THIS AFTEROON ALONG AND EAST OF THE
LARAMIE AND INTO THE NEBRASKA PANHANDLE. NORTH TO NORTHWEST WINDS
WILL FREQUENTLY GUST TO AROUND 40 MPH. WINDS WILL DIMINISHQUICKLY
THIS AROUND SUNSET THIS EVENING.

&&

.FIRE WEATHER...
ISSUED AT 256 AM MST SUN NOV 16 2014

NO FIRE WEATHER CONCERNS OVER THE NEXT SEVERAL DAYS WITH A CONTINUED
COOL WEATHER PATTERN AND RECENT SNOWFALL. WEST-TO-NORTHWEST WINDS
WILL GUST AS HIGH AS 40 MPH ACROSS EASTERN WY AND THE WESTERN NE
PANHANDLE TODAY AS A STRONG WEATHER SYSTEM MOVES SOUTH ACROSS THE
WESTERN DAKOTAS. CONSIDERABLE BLOWING SNOW WILL BE POSSIBLE ALONG
AND NORTH OF A LINE FROM DOUGLAS TO ALLIANCE. HIGH WINDS WILL AGAIN
BE POSSIBLE OVER THE WIND PRONE LOCATIONS OF SOUTHEAST WY ON TUE.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR WYZ101-
     102.

NE...WINTER WEATHER ADVISORY UNTIL 6 PM MST THIS EVENING FOR NEZ002-
     095.

&&

$$

UPDATE...CLH
SHORT TERM...CLH
LONG TERM...GCC
AVIATION...SML
FIRE WEATHER...CLH



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