FXUS65 KCYS 070959
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
259 AM MST MON DEC 7 2009

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT...

HAVE DECIDED TO GO WITH A WINTER STORM WATCH FOR TONIGHT THROUGH
TUESDAY WITH SOMEWHAT LOW CONFIDENCE. NO DOUBT SOME AREAS WILL GET
DECENT SNOW WITH THE APPROACHING SYSTEM OVERRUNNING THE ARCTIC
AIR MASS IN PLACE OVER THE CWA. FORECAST PROBLEM AS USUAL WILL BE
THE TIMING AND AMOUNTS.

SURFACE HIGH PRESSURE IN PLACE WITH TEMPERATURES IN THE SINGLE
DIGITS ON BOTH SIDES OF ZERO. AREAS OF LIGHT SNOW BEING REPORTED.
ALOFT STRONG JET ORIENTED WEST TO EAST JUST TO THE SOUTH OF
WYOMING. UPPER LOW OVER NORTHERN CALIFORNIA AND SOUTHERN OREGON
WITH SEVERAL SHORT WAVES ROTATING AROUND THE LOW. 50+ METER HEIGHT
FALLS AT BOTH 5/7H ASSOCIATED WITH THE LOW.

MODELS SHOW UPPER FLOW BACKING WITH TIME AS THE SYSTEM MOVES EAST.
PRECIPITATION WILL INCREASE IN COVERAGE AND INTENSITY LATER THIS
AFTERNOON WITH THE HEAVIEST SNOW AFTER MIDNIGHT TONIGHT. GUIDANCE
FROM HPC HAS SOME AREAS IN THE MOUNTAINS OVER 12 INCHES WITH 4 TO
8 IN THE LOWER ELEVATIONS. SO IT MAY BE A MARGINAL EVENT.

TEMPERATURES WILL CONTINUE TO BE MUCH BELOW NORMAL. 

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY...
VERY COLD CONDITIONS WILL CONTINUE TO BE PRESENT...ESPECIALLY WITH 
MORE NEW SNOW COVER EXPECTED FROM THE TUESDAY STORM SYSTEM. LOWS 
TUESDAY NIGHT ARE EXPECTED TO BE 15 TO 20 DEGREES BELOW 
NORMAL...WITH MOST AREAS EXPECTED TO SEE BELOW ZERO READINGS. 
PRECIPITATION WILL CONTINUE TO DECREASE TUESDAY NIGHT WITH EVEN SOME 
CLEARING OF SKIES EXPECTED TO ENHANCE THE OVERNIGHT COOLING. 
PRECIPITATION CHANCES WILL LINGER LONGEST IN THE NEBRASKA PANHANDLE. 
ORTHOGRAPHIC SNOW SHOWERS WILL ALSO CONTINUE AS DEEP NORTH-NORTHWEST 
FLOW DEVELOPS. THE STRONGEST JET ENERGY WILL FINALLY BE AROUND THE 
BASE OF THE VERY LARGE UPPER LOW EXPECTED TO BE CENTERED AT AROUND 
70N 100W WEDNESDAY. THIS WILL RESULT IN A DEEPENING CYCLONE ACROSS 
THE GREAT LAKES AND NORTHEAST STATES. THIS STORM SYSTEM IN THE EAST 
IS IMPORTANT DUE TO ITS ELONGATING THE UPPER FLOW INTO A MORE ZONAL 
FLOW PATTERN LATE IN THE WEEK AND INTO NEXT WEEKEND. THE FAVORED 
EUROPEAN MODEL SOLUTION THEN BRINGS AN EASTERN PACIFIC UPPER LOW TO 
THE CALIFORNIA COAST INDUCING HEIGHT RISES OVER THE ROCKIES AND HIGH 
PLAINS. SHORT-WAVE ENERGY IN THE RESULTING MOIST SOUTHWEST FLOW WILL 
KEEP NEAR CLIMATOLOGICAL CHANCES FOR SHOWERS ACROSS THE WESTERN 
PORTION OF THE FORECAST AREA. THE HEIGHT RISES WILL HELP TO PUSH THE 
VERY COLD SURFACE HIGH PRESSURE AREA FARTHER EAST AND ALLOW FOR 
MODERATING TEMPERATURES TO WITHIN 5 DEGREES OF NORMAL SATURDAY AND 
EVEN TO NEAR NORMAL VALUES SUNDAY. TEMPERATURES WILL COOL TO 
SLIGHTLY BELOW NORMAL MONDAY AS ANOTHER DISTURBANCE IN THE SOUTHERN 
STREAM WILL ALLOW THE COLD SURFACE HIGH TO SHIFT WEST AGAIN. 

&&

.AVIATION...WIDESPREAD AREAS OF LOW CLOUDS AND LIGHT SNOW WILL
CONTINUE TO PRODUCE PERIODS OF IFR/MVFR AT ALL LOCATIONS THROUGH
TUESDAY. 

&&

.FIRE WEATHER...NO FIRE WEATHER CONCERNS THIS FORECAST PERIOD.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WATCH FROM 5 PM MONDAY TO 5 PM TUESDAY FOR WYZ103-
     WYZ106-WYZ107-WYZ108-WYZ110-WYZ112-WYZ113-WYZ114-WYZ115-
     WYZ116-WYZ117-WYZ118-WYZ119.
NE...WINTER STORM WATCH FROM 5 PM MONDAY TO 5 PM TUESDAY FOR NEZ002-
     NEZ003-NEZ019-NEZ020-NEZ021-NEZ054-NEZ055-NEZ095-NEZ096.

&&

$$

SHORT TERM/AVIATION...GRIFFITH
LONG TERM...CARPENTER