HAMweather.com Area Forecast Discussion for County Warning Area CYS

Thu, 16 Feb 2012 06:33:02 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1056 PM MST WED FEB 15 2012

.AVIATION...06Z TAF ISSUANCE...
MVFR CIGS/VSBYS STILL ANTICIPATED AFTER 10Z AS FOG IS EXPECTED TO
DEVELOP IN LIGHT WINDS AND CLEARING SKIES AT KRWL AND KLAR. A FEW
LIGHT SNOW SHOWERS WILL LINGER ALONG THE SOUTHERN
LARAMIE/SNOWY/SIERRA MADRE RANGES THROUGH 08Z RESULTING IN
MOUNTAIN OBSCURATIONS. OTHERWISE...VFR CONDITIONS ARE ANTICIPATED
AT KCYS AND WESTERN NEBRASKA TERMINALS. ANY PATCHY FOG THAT DOES
FORM AT KRWL AND KLAR WILL LIFT BY AROUND 14Z...GIVING WAY TO VFR
AND INCREASINGLY BREEZY CONDITIONS DURING THE AFTERNOON HOURS.
HAHN

PREV DISCUSSION... /ISSUED 338 PM MST WED FEB 15 2012/ 

SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT...WATER VAPOR IMAGERY
SHOWS A BROAD...POSITIVELY TILTED TROUGH OVER NORTH AMERICA WITH A
NUMBER OF UPPER LEVEL DISTURBANCES EMBEDDED IN IT. THIS WILL KEEP
THE MAIN JET STREAM WELL SOUTH AND EAST OF WYOMING AND NEBRASKA
THROUGH THE SHORT TERM PERIOD. ONE WEATHER SYSTEM TO MENTION IS
CURRENTLY DIGGING SOUTH THROUGH CALIFORNIA AND NEVADA AND WILL
EVENTUALLY TRACK EAST THROUGH TEXAS ON FRIDAY/FRIDAY NIGHT. A
SECOND IS SKIRTING ACROSS THE NORTHERN PLAINS...WITH SOME WEAK
ENERGY MOVING ACROSS THE FORECAST AREA BETWEEN THE TWO SYSTEMS.
SOUTHWEST FLOW AHEAD OF THE CALIFORNIA STORM IS ADVECTING SOME
MOISTURE INTO THE FORECAST AREA TODAY AND IS COMBINING WITH THE
WEAK ENERGY TO CREATE SOME CONVECTIVE TOWERS OVER THE MOUNTAINS
AND FAR NORTHERN ZONES AS SEEN ON VISIBLE IMAGERY THIS AFTERNOON.
RUC ANALYSIS SHOWS SOME WEAK INSTABILITY PERSISTING THROUGH THE
EARLY EVENING OVER THE WESTERN PEAKS...SO MAINTAINED CHANCE FOR
SNOW SHOWERS HERE. ALSO INCREASED POPS TO SLIGHT CHANCE FOR THE
LARAMIE RANGE WITH FLURRIES VICINITY THESE LOCATIONS...INCLUDING
THE FAR NORTHERN ZONES. RESIDUAL LOW LEVEL MOISTURE WILL PRODUCE
PATCHY FOG TONIGHT MAINLY IN THE LOWER ELEVATIONS WEST OF THE
LARAMIE RANGE. SHOULD SEE TEMPS DROP PRETTY GOOD TONIGHT ACROSS
THE ENTIRE FORECAST AREA IN THIS POST-FRONTAL AIRMASS...WITH
MOSTLY SINGLE DIGITS TO LOW TEENS EXPECTED.

TOMORROW WILL BE A FEW DEGREES WARMER THAN TODAY WITH MORE AVAILABLE 
SUNSHINE AS THE UPPER TROUGH SHIFTS SLIGHTLY TO THE SOUTHEAST. THIS 
WILL BE SHORTLIVED AS ANOTHER CLIPPER SYSTEM DIVES DOWN FROM THE PAC 
NW THURSDAY NIGHT. ANOTHER COLD FRONT WILL MOVE ACROSS THE AREA 
DURING THIS TIME AS WELL. FRIDAY WILL BE COOLER ONCE AGAIN WITH A 
CHANCE FOR MOUNTAIN SHOW SHOWERS WITH FLURRIES NEARBY. MODELS ARE 
NOT SHOWING MUCH MOISTURE BEING BROUGHT DOWN WITH THIS SYSTEM...BUT 
SHOULD BE ENOUGH FOR COLD AIR ADVECTION AND OROGRAPHIC EFFECTS TO 
SQUEEZE OUT SOME LIGHT SNOW/FLURRIES. AHEAD OF THE FRONT...PRESSURE 
FALLS ACROSS THE EASTERN PLAINS SHOULD CONTRIBUTE TO A STRENGTHENING 
OF THE SOUTHWEST TO NORTHEAST PRESSURE GRADIENT AND THUS A RETURN OF 
MODERATE SOUTHWEST WINDS IN THE WIND CORRIDOR THURSDAY NIGHT. BREEZY 
NORTHWEST WINDS WILL BECOME WIDESPREAD BEHIND THE FRONT FOR FRIDAY.

LONG TERM...SATURDAY THROUGH WEDNESDAY...LONG RANGE MODELS IN
GOOD AGREEMENT WITH THE OVERALL PATTERN...AND GENERALLY SHOW 
NORTH TO NORTHWEST FLOW ALOFT WHICH WILL LIKELY KEEP TEMPERATURES
NEAR NORMAL OR SLIGHTLY BELOW NORMAL THROUGH EARLY NEXT WEEK.
HOWEVER...MODELS CONTINUE TO BE INCONSISTENT WITH THE UPPER LEVEL
TROUGH AND ASSOCIATED COLD FRONT FOR LATE SUNDAY AND THROUGH
MONDAY...ALTHOUGH THEY ARE TRENDING TOWARDS ONE SOLUTION. THE GEM
IS THE MOST PROGRESSIVE...SHOWING THE TROUGH REMAINING AS AN OPEN
WAVE AS IT QUICKLY MOVES ACROSS WYOMING SUNDAY NIGHT PRODUCING
LIGHT PRECIP OVER MOST OF THE AREA. THE 12Z ECMWF SHOWS THE SYSTEM
ATTEMPTING TO SPLIT AS IT ROUNDS THE BASE OF THE MAIN UPPER LEVEL
TROUGH FURTHER NORTH IN SOUTHERN ALBERTA...BUT INSTEAD PROGRESSES
EASTWARD INTO COLORADO AND WYOMING PRODUCING WIDESPREAD LIGHT TO
MODERATE SNOWFALL ACROSS THE AREA INCLUDING WESTERN NEBRASKA. THE
DGEX...GFS...AND MOST OF THE ENSEMBLES ON THE OTHER HAND SHOW THE
SYSTEM SPLITTING AS IT DIGS SOUTHWARD WEST OF WYOMING AND
COLORADO. GIVEN THE RECENT PATTERN OF SPLIT FLOW WITH SYSTEMS
DIGGING SOUTH OF THE FORECAST AREA OVER THE LAST 5 DAYS...PREFER
THE GFS/ENSEMBLE SOLUTION. MOST AREAS SHOULD SEE AT LEAST SOME
LIGHT PRECIPITATION ALONG AND WEST OF THE LARAMIE RANGE...SO
INCREASED POP WEST OF A LINE FROM CHEYENNE TO DOUGLAS INCLUDING
THE MOUNTAINS. KEPT POP AROUND 25 TO 30 PERCENT EAST OF THE
LARAMIE RANGE SUNDAY THROUGH MONDAY MORNING. KEPT HIGH
TEMPERATURES IN THE 30S AND 40S ACROSS THE AREA WITH THE EXCEPTION
OF SUNDAY AHEAD OF THE COLD FRONT. INCREASED TEMPERATURES ACROSS
FAR SOUTHEAST WYOMING AND WESTERN NEBRASKA AHEAD OF THE FRONT. DO
NOT EXPECT A MAJOR SNOWSTORM WITH THIS FEATURE...BUT WILL CONTINUE
TO MONITOR THROUGH THE END OF THIS WEEK.

AFTER A BRIEF BREAK LATE MONDAY AND TUESDAY...MODELS SHOW A STRONG
140 KNOT JET STREAM MOVING INTO WYOMING FROM THE NORTHWEST WITH
NORTH TO NORTHWEST FLOW ALOFT. EXPECT ANOTHER CHANCE OF SNOW BY
WEDNESDAY...ESPECIALLY ACROSS THE MOUNTAINS WITH UPSLOPE FLOW.
STRONG WINDS WILL ALSO BECOME AN ISSUE TUESDAY AND WEDNESDAY AS
THE STRONG JET ALOFT AS WELL AS 700MB WINDS OVER 50 KNOTS IMPACT
SOUTHEAST WYOMING.

 

.FIRE WEATHER...FIRE WEATHER CONCERNS WILL REMAIN LOW ACROSS THE 
DISTRICT DUE TO RESIDUAL SNOWPACK AND PACIFIC MOISTURE MOVING INTO 
THE AREA. THERE WILL BE CHANCES FOR SNOW SHOWERS FOR THE SNOWY AND 
SIERRA MADRE MOUNTAINS TONIGHT AND AGAIN ON FRIDAY...WITH DRIER 
CONDITIONS DISTRICT-WIDE ON THURSDAY. THE NEXT CHANCE FOR 
SIGNIFICANT PRECIPITATION WILL BE LATE THIS WEEKEND INTO EARLY NEXT 
WEEK. LIGHT WEST TO NORTHWEST WINDS TODAY WILL BECOME BREEZY 
TOMORROW AND TOMORROW NIGHT ACROSS SOUTHEAST WYOMING AHEAD OF A COLD 
FRONT MOVING SOUTH ACROSS THE EASTERN PLAINS TOMORROW NIGHT. GUSTS 
OF 25 TO 35 MPH ARE POSSIBLE. WINDS WILL SHIFT TO THE NORTHWEST AND 
REMAIN BREEZY THROUGH FRIDAY BEHIND THE FRONT. 

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