Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 042332 CCA
AFDCYS

AREA FORECAST DISCUSSION...CORRECTED AVIATION
NATIONAL WEATHER SERVICE CHEYENNE WY
327 PM MDT MON MAY 4 2015

.SHORT TERM...(TONIGHT THROUGH WEDNESDAY NIGHT)
ISSUED AT 325 PM MDT MON MAY 4 2015

THE AFTERNOON WATER VAPOR LOOP DEPICTED A SPLIT FLOW ALOFT WITH
NORTHERN STREAM UPPER LOW SPINNING NEAR THE GULF OF AK AND UPPER
TROUGH NORTH OF THE GREAT LAKES. THE SUBTROPICAL JET WAS RATHER
ACTIVE WITH A NEARLY STATIONARY UPPER LOW OVER SOUTHERN CA.
DIFFLEUNT SOUTHERLY FLOW FROM THE SOUTHWEST INTO THE CENTRAL AND
SOUTHERN ROCKIES AND INSTABILITY RESULTED IN FAIRLY WIDESPREAD
CONVECTIVE COVERAGE. AT THE SURFACE...A STALLED BOUNDARY EXTENDED
FROM LOWER MI ACROSS NORTHERN MO... CENTRAL KS THEN NORTH ALONG
THE FRONT RANGE INTO SOUTHWEST WY. WITH THE MORE STABLE AIR MASS
EAST OF THE LARAMIE RANGE... SCATTERED RAIN SHOWERS PREVAILED.
INSTABILITY /LI`S 0 TO -2C/ WEST OF THE LARAMIE RANGE RESULTED IN
ISOLATED TO SCATTERED TSTORMS. STRONGER STORMS MAY PRODUCE BRIEF
SMALL HAIL... GUSTY WINDS AND HEAVY RAIN AS THEY MOVE NORTHEAST
THROUGH LATE AFTERNOON.

THE LATEST DETERMINISTIC NUMERICAL MODEL GUIDANCE MAINTAINS THE
MOIST AND UNSETTLED WEATHER PATTERN THROUGH THE SHORT TERM. THE
SOUTHERN CA LOW WILL GRADUALLY WEAKEN TO AN OPEN WAVE AS IT
LIFTS NORTHEAST ACROSS THE FOUR CORNERS...CENTRAL ROCKIES AND
NORTHERN PLAINS BY THE END OF THE PERIOD. MEANWHILE...THE GULF
OF AK LOW WILL MOVE ONSHORE INTO WA TUESDAY...THEN EXPAND AND
DIG SOUTH THROUGH OR AND CA BY WEDNESDAY NIGHT.

TSTORM ACTIVITY OUT WEST WILL LINGER THROUGH EARLY EVENING THEN
DECREASE TO SHOWERS WITH STABILIZING LOWER LEVELS. CONCERN WILL
TURN TO FOG POTENTIAL AS MOIST SOUTHERLY BOUNDARY LAYER FLOW
CONTINUES. INSERTED AREAS OF FOG IN THE GRIDS FROM THE SOUTHERN
LARAMIE RANGE EAST INTO THE SOUTHERN NE PANHANDLE TONIGHT AND
TUESDAY MORNING. COULD SEE LOCALLY DENSE FOG AT THE SUMMIT AND
NEARBY FOOTHILLS.

THE MOIST SOUTHERLY FLOW ALOFT COMBINED WITH SEVERAL TRANSIENT
WEAK UPPER LEVEL WAVES WILL KEEP SHOWERS AND OCCASIONAL TSTORMS
IN THE FORECAST THROUGH WEDNESDAY NIGHT. THE BEST CHANCES FOR
MORE ORGANIZED TSTORM ACTIVITY WILL BE TUESDAY AFTERNOON AND
EVENING AS THE UPPER TROUGH MOVES THROUGH THE CENTRAL ROCKIES.
MODEL LI`S LOWER TO -1 TO -3C WITH 50+ DEGREE DEW POINTS
ADVECTING NORTH-NORTHWEST INTO THE HIGH PLAINS...GENERALLY EAST
OF I-25. SURFACE-BASED CAPES OF 500-1000 J/KG MAXIMIZE LATER
IN THE AFTERNOON AS TEMPERATURES RISE INTO THE LOW-MID 60S.
LOW/MID LEVEL SHEAR VALUES ARE RELATIVELY WEAK...BUT SUFFICIENT
FOR SOME STRONGER CELLS TO PRODUCE HAIL UP TO NICKEL SIZE.
PRECIP WATER VALUES WILL VARY BETWEEN 0.60" WEST TO AROUND AN
INCH EAST TUESDAY...SO THE POTENTIAL IS THERE FOR LOCALLY HEAVY
RAINFALL WITH THE STRONGER CELLS.

TSTORMS MAY LINGER AS LATE AS MIDNIGHT TUESDAY NIGHT BEFORE
DECREASING TO SHOWERS WITH THE DIFFLUENT SOUTHERLY FLOW ALOFT.
PATCHY TO AREAS OF FOG WILL ONCE AGAIN BE POSSIBLE FOR THE
SAME AREAS AS TONIGHT.

A PACIFIC COLD FRONT WILL BE MOVING EAST ACROSS THE CWA WEDNESDAY
AFTERNOON...WITH WINDS SHIFTING TO THE NORTHWEST AND BECOMING
GUSTY. AIR MASS DOES NOT LOOK AS UNSTABLE AS TUESDAY...WITH MAINLY
ISOLATED TSTORMS EXPECTED. TEMPERATURES WILL BE MILDEST ACROSS THE
PLAINS WITH HIGHS IN THE 60S...WHILE COOLER 40S AND 50S PREVAIL
OUT WEST.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 300 PM MDT MON MAY 4 2015

THE MILD AND MOIST PATTERN LOOKS TO PERSIST ACROSS THE CWA FOR
MUCH OF THE PERIOD AS ANOTHER UPPER LOW DIGS OVER THE DESERT SW
THURSDAY AND FRIDAY...THEN LIFTS NORTHEAST ACROSS COLORADO INTO
THE CENTRAL PLAINS OVER THE WEEKEND. SEVERAL IMPULSES WILL EJECT
NORTHEAST ACROSS THE CWA AHEAD OF THE UPPER LOW WHICH WILL BRING
PERIODS OF SHOWERS ACROSS MUCH OF THE CWA THURSDAY AND FRIDAY. A
MORE GENERAL RAIN EXPECTED SATURDAY AND SUNDAY AS THE MAIN UPPER
LOW COMES BY WITH LEE CYCLONE DEEPENING OVER FAR EASTERN COLORADO
SAT NIGHT BEFORE LIFTING ACROSS NEBRASKA ON SUNDAY. DECENT QPF
LOOKING A GOOD BET OVER THE WEEKEND AND OF PARTICULAR INTEREST
WILL BE SNOW LEVELS SATURDAY NIGHT INTO SUNDAY AS THICKNESSES FALL
BELOW 550DM ACROSS SE WY INTO THE NE PANHANDLE. MODELS IN PRETTY
GOOD AGREEMENT WITH THIS SYSTEM. WILL HAVE TO WATCH CLOSELY OVER
THE NEXT FEW DAYS. SHOULD CLEAR OUT SUNDAY NIGHT AS THE UPPER LOW
OPENS AND MOVES INTO THE NORTHERN PLAINS WITH MILD AND MAINLY DRY
WEATHER MONDAY UNDER A TRANSIENT RIDGE ALOFT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH TUESDAY AFTERNOON)

MARGINAL MVFR CIGS LIKELY TO CONTINUE TO AFFECT PORTIONS OF
SOUTHEAST WYOMING THIS EVENING BEFORE LOWERING TO LIFR TONIGHT AND
INTO TUESDAY MORNING DUE TO LOCALLY DENSE FOG AND LOW CIGS. PATCHY
FOG AND LOW CIGS MAY DEVELOP OVER THE SOUTHERN NE PANHANDLE AS WELL
BY EARLY TUESDAY MORNING WITH IFR CONDITIONS EXPECTED.
OTHERWISE...CONDITIONS WILL IMPROVE BY THE MIDDLE OF THE MORNING AS
ANOTHER ROUND OF SHOWERS AND TSTORMS IS EXPECTED BY TUESDAY
AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 232 PM MDT MON MAY 4 2015

A MOIST AND UNSETTLED WEATHER PATTERN WILL DOMINATE THE DISTRICTS
AS A SLOW MOVING LOW PRESSURE SYSTEM MOVES FROM THE FOUR CORNERS
REGION ACROSS THE CENTRAL AND SOUTHERN ROCKIES THROUGH MID WEEK.
SHOWERS WITH ISOLATED TO SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS WILL DEVELOP EACH DAY. LOCALLY HEAVY RAIN...GUSTY
WINDS AND SMALL HAIL WILL BE POSSIBLE WITH THE STRONGER STORMS. A
PACIFIC COLD FRONT WILL PASS THROUGH THE DISTRICTS WEDNESDAY...
FOLLOWED BY ANOTHER LOW PRESSURE SYSTEM BY THIS WEEKEND. COOLER
TEMPERATURES WITH RAIN AND SNOW WILL ACCOMPANY THIS SYSTEM.

&&

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

$$

SHORT TERM...MJ
LONG TERM...RE
AVIATION...TJT
FIRE WEATHER...MJ



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