FXUS65 KCYS 052018
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
120 PM MST SAT DEC 5 2009

.SHORT TERM...TONIGHT THROUGH MONDAY...
RESPITE FROM VERY COLD TEMPERATURES WILL COME TO AN END TONIGHT AS 
NEXT SURGE OF ARCTIC AIR INVADES THE REGION WHILE UPPER LOW SETTLES 
OVER THE NW CONUS.  SATELLITE SHOWING SLOWLY EXPANDING/COOLING CLOUD 
TOPS NOW OVER WESTERN WY AND EXPECT LIGHT SNOW TO SPREAD OVER THE 
CWA OVERNIGHT AS SFC UPSLOPE FLOW INCREASES UNDER WESTERLY 
OVERRUNNING FLOW ALOFT. RATHER DIFFLUENT UPPER FLOW EXPECTED TO SET 
UP OVER THE REGION SUNDAY WHICH WILL KEEP LIGHT SNOW GOING OVER THE 
AREA. TEMPERATURE PROFILES NOT REAL FAVORABLE FOR DENDRITIC SNOW 
GROWTH THUS SNOWFALL AMOUNTS BY SUNDAY EVENING EXPECTED TO REMAIN 
GENERALLY IN THE 3-5 INCH RANGE OVER LOWER ELEVATIONS OF WY WITH 
6-10 INCHES OVER HIGHER TERRAIN.  AFTER COORDINATION WITH 
SURROUNDING OFFICES HAVE POSTED A WINTER WEATHER ADVISORY FOR MUCH 
OF THE WY PORTION OF THE CWA.  FORTUNATELY WINDS NOT LOOKING TOO 
STRONG BUT SOME AREAS OF BLOWING/DRIFTING SNOW POSSIBLE AS THE SNOW 
WILL BE QUITE DRY AND FLUFFY.  EXPECT SNOW TO TAPER OFF TO MOSTLY 
FLURRIES SUNDAY NIGHT INTO MONDAY AS INITIAL SYSTEM MOVES AWAY AND 
BETTER UPSLOPE FLOW SETTLES INTO COLORADO BUT THEN INCREASING AGAIN 
OUT WEST MONDAY AFTERNOON AS NEXT UPPER SYSTEM APPROACHES. VERY COLD 
TEMPERATURES WILL SETTLE OVER THE CWA SUNDAY THROUGH MONDAY AS SFC 
RIDGE BUILD SOUTH OVER THE HIGH PLAINS WITH MAX TEMPERATURES LIKELY 
STRUGGLING TO REACH THE TEENS SUNDAY.  A BIT WARMER ON MONDAY AS 
HEIGHTS RISE A BIT BUT STILL VERY COLD.          

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY. DECENT CONFIDENCE IN GFS 
AND ECMWF MODEL SOLUTIONS SINCE THEIR 500 MB PATTERNS QUITE SIMILAR.

MONDAY NIGHT...LIGHT TO MODERATE SNOW WILL BE INCREASING IN COVERAGE 
AND INTENSITY AS NEXT SHORTWAVE TROUGH APPROACHES FROM UTAH AND LIFT 
IS PROVIDED BY IMPRESSIVE WARM AIR ADVECTION ALOFT OVER THE LOW 
LEVEL COLD DOME COMBINED WITH UPSLOPE MECHANICAL LIFT OF THE DEEPLY 
SATURATED AIRMASS. BOOSTED SNOW CHANCES. EXPECT EVEN HIGHER POPS AS 
THIS PERIOD APPROACHES AS NEARLY ALL AREAS WILL GET MEASURABLE SNOW.

TUESDAY...PROGRESSIVE SHORTWAVE TROUGH MOVES TO WESTERN NEBRASKA AND 
WESTERN KANSAS BY LATE AFTERNOON WITH COLDER AIR PLUNGING SOUTH 
ACROSS OUR COUNTIES IN THE AFTERNOON. WIDESPREAD LIGHT TO MODERATE 
SNOW EXPECTED. BITTERLY COLD HIGH TEMPERATURES WITH 700 MB 
TEMPERATURES NEAR -22 CELSIUS AND 1000-500 MB THICKNESSES NEAR 5190 
METERS.

WEDNESDAY...CONTINUED VERY COLD AS CYCLONIC FLOW ALOFT CONTINUES 
ACROSS THE NORTHERN ROCKIES AND NORTHERN PLAINS STATES WITH 500 MB 
HEIGHTS NEAR 5310 METERS ACROSS OUR COUNTIES. HIGH TEMPERATURES IN 
THE SINGLE DIGITS AND TEENS WITH 1000-500 MB THICKNESSES NEAR 5130 
METERS. OROGRAPHIC SNOW SHOWERS ACROSS THE SNOWY RANGE IN MOIST 
NORTHWEST FLOW ALOFT.

THURSDAY...FLOW ALOFT BECOMES WEST AND TEMPERATURES WILL WARM INTO 
THE MID 20S TO LOWER 30S AS HEIGHTS ALOFT RISE AND 1000-500 MB 
THICKNESSES RISE TO NEAR 5370 METERS.

FRIDAY/SATURDAY...RELATIVELY MILD TEMPERATURES...COMPARED TO EARLY 
THIS WEEK...WILL CONTINUE AS NEARLY ZONAL FLOW CONTINUES. SCATTERED 
OROGRAPHIC SNOW SHOWERS ACROSS OUR WESTERN COUNTIES AND THE SNOWY 
RANGE IN MOIST FLOW ALOFT. 

&&

.AVIATION...CEILINGS AND VISIBILITIES WILL BE LOWERING TO LIFR AND 
IFR OVERNIGHT AS SNOW AND FOG BECOME MORE WIDESPREAD. IFR AND MVFR 
WILL CONTINUE IN SNOW AND FOG ON SUNDAY AND SUNDAY NIGHT.

&&

.FIRE WEATHER...NO CONCERNS THROUGH MONDAY WITH VERY COLD 
TEMPERATURES AND SNOWFALL.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY FROM 5 PM SATURDAY TO 6 PM SUNDAY FOR
     WYZ101-WYZ103>WYZ105.
     WINTER WEATHER ADVISORY FROM 9 PM SATURDAY TO 6 PM SUNDAY FOR
     WYZ106-WYZ107-WYZ109>WYZ118.
NE...NONE.

&&

$$

SHORT TERM/FIRE WEATHER...RE
LONG TERM/AVIATION...RUBIN