Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 311749 CCA
AFDCYS

AREA FORECAST DISCUSSION...CORRECTED UPDATE
NATIONAL WEATHER SERVICE CHEYENNE WY
1147 AM MDT FRI OCT 31 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 352 AM MDT FRI OCT 31 2014

MAIN FORECAST IMPACT TODAY WILL BE MORNING FOG. 09Z SATELLITE FOG
PRODUCT SHOWS WELL DEFINED AREA OF LOW CLOUDS/FOG EXTENDING FROM
NORTHEAST WY THRU AREAS NORTH OF THE PINE RIDGE...SOUTHEAST INTO
CENTRAL NEBRASKA. THIS IN LIGHT EASTERLY FLOW AS 1040MB SFC HIGH
SETTLES INTO THE DAKOTAS. LLVL INVERSION IS STEEPENED BY AN
APPROACHING UPSTREAM RIDGE. DEW POINT DEPRESSIONS ARE WITHIN 2-3F
ACROSS THE WRN NEBRASKA PANHANDLE AND AREAS IN SE WY ALONG THE
STATELINE. LATEST HRRR SHOWS THE AREA OF FOG PROGRESSING WESTWARD
INTO THE WRN NEBRASKA PANHANDLE THRU DAYBREAK AND INTO THE SE
WYOMING PLAINS SHORTLY THEREAFTER. THIS SOLUTION SEEMS REASONABLE
GIVEN EARLY MORNING DEW POINT DEPRESSION TRENDS. FOG LOOKS TO BE
FAIRLY PATCHY AT THIS POINT...ALTHOUGH IT MAY BE LOCALLY DENSE IN
SOME AREAS. THE LATEST HRRR SHOWS FOG /LOW CLOUDS PERSISTING
ACROSS LARAMIE COUNTY THE LONGEST THIS MORNING NOT DISSIPATING
UNTIL AROUND MIDDAY. OTHERWISE...A DRY DAY AHEAD AS RIDGE AXIS
PASSES THRU THE CWFA. CLOUDS WILL BE ON THE INCREASE THO AS WELL
AS MOISTURE ABOVE H5 BUMPS INTO THE RIDGE AXIS. THE OTHER CONCERN
TODAY IS THE POTENTIAL FOR WIND ADVISORY SPEEDS IN THE NRN
NEBRASKA PANHANDLE...SPECIFICALLY NR THE PINE RIDGE. ALL OUTPUT IS
POINT TO MARGINAL WINDS WITH A LOCAL MAXIMUM OVR THE PINE RIDGE.
MODELS OFTEN UNDERDO WIND SPEEDS FOR THIS AREA IN STRONG SSE SFC
FLOW. SO...WILL ISSUE A WIND ADVISORY FOR SIOUX...DAWES...AND BOX
BUTTE COUNTIES EFFECTIVE 16Z-01Z TODAY.

FLOW BACKS TO THE SOUTHWEST AHEAD OF THE WRN CONUS TROUGH FOR
SATURDAY. THIS WILL RESULT IN THE WARMEST DAY OF THE PERIOD AS THE
LEE-SIDE TROUGH DEVELOPS AND AMPLIFIES. HIGH TEMPS SATURDAY WILL
RISE WELL INTO THE 60S WITH LOW 70S ACROSS E-C WY AND PORTIONS OF
THE WRN NE PANHANDLE. BREEZY CONDITIONS WILL DEVELOP...SOUTHWEST AT
20 TO 30 MPH WEST OF THE LARAMIE RANGE...SOUTH/SOUTHEAST AT 10 TO 20
MPH OUT ON THE ERN PLAINS.

MODELS CONTINUE TO SPLIT THE ENERGY OF THE NEXT TROUGH ON
SUNDAY...WITH ONE PIECE EJECTING NORTHEAST ACROSS MONTANA WHILE THE
SOUTHERN SYSTEM APPROACHES THE FOUR CORNERS. THIS MEANS A LATER
ARRIVAL IN PRECIP CHANCES...WHICH WILL LIKELY NOW HOLD OFF UNTIL
SUNDAY AFTERNOON OR AFTER. BEST CHANCES WILL BE IN OROGRAPHICALLY
FAVORED AREAS OF THE SNOWY AND SIERRA MADRE RANGES. THICKER CLOUD
CANOPY AND APPROACHING COLD FRONT WILL YIELD A COOLER DAY
SUNDAY...WITH HIGHS NR 50 WEST AND IN THE UPPER 50S AND LOW 60S
EAST.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 352 AM MDT FRI OCT 31 2014

LONG RANGE MODELS CONTINUE TO COME INTO BETTER AGREEMENT WITH THE
PACIFIC STORM SYSTEM FORECAST TO PUSH ACROSS THE CENTRAL ROCKY
MOUNTAINS EARLY NEXT WEEK. MODELS INDICATE SPLIT FLOW WILL DEVELOP
ACROSS THE GREAT BASIN REGION LATE THIS WEEK...AND IT APPEARS THE
SOUTHERN PORTION OF THE ENERGY AND UPPER JET WILL IMPACT SOUTHEAST
WYOMING AND WESTERN NEBRASKA AS THE NORTHERN PORTION WILL BE
EJECTED NORTHEAST INTO MONTANA ON SUNDAY. THIS WILL ALLOW THE
SOUTHERN BRANCH OF THE JET TO BECOME MORE DOMINANT INTO EARLY
MONDAY MORNING...WITH THE POTENTIAL FOR RAIN/SNOW ALONG I80.
MODELS ARE TRENDING SLOWER WITH THE SOUTHERN SYSTEM...WITH MOST OF
THE PRECIPITATION HOLDING OFF UNTIL MONDAY. THE ECMWF IS THE MOST
AGGRESSIVE...WITH THE GFS AND NAM A CLOSE SECOND...SHOWING DECENT
QPF AMOUNTS AS A 100KT JET DEVELOPS AND PUSHES NORTHWARD OUT OF
THE SOUTHWEST UNITED STATES. EVEN WITH THE INCONSISTENCIES BETWEEN
INDIVIDUAL MODEL RUNS REGARDING TIMING BETWEEN SUNDAY AND
MONDAY...CURRENT 00Z MODELS ARE IN GOOD ENOUGH AGREEMENT TO
INCREASED POP BETWEEN 30 TO 50 PERCENT ALONG THE I80 CORRIDOR
NORTHWARD TO THE PLATTE RIVER VALLEY. EXPECT RAIN TO MIX WITH AND
CHANGE TO SNOW DOWN TO 5500 FEET. HOWEVER...ACCUMULATIONS APPEAR
MINIMAL AT THIS TIME SINCE MOST OF THE PRECIP WILL OCCUR DURING
THE DAY...BUT WILL KEEP AN EYE ON THIS AS SOME SLIGHT TIMING
DIFFERENCES ARE LIKELY. TEMPERATURES ON MONDAY ARE EXPECTED TO BE
10 TO 15 DEGREES BELOW NORMAL WITH HIGHS STRUGGLING TO REACH 4O TO
45 DEGREES...AND MODELS CONTINUE TO TREND COOLER...SO THESE VALUES
MAY BE A LITTLE TOO HIGH. LOW TEMPERATURES IN THE TEENS TO MID
20S ARE EXPECTED BY LATE MONDAY NIGHT AS THE COOLER AIR SETTLES
OVER THE REGION...BUT WITH SOME CLOUD COVER OVER THE
AREA...TEMPERATURES WILL PROBABLY NOT LOWER ANY COLDER THAN 20 IN
MOST LOCATIONS. PRECIPITATION WILL BE PRETTY LIGHT FURTHER TO THE
NORTH BUT MAY SEE MODERATE QPF VALUES AROUND 0.50 INCHES ALONG THE
I80 CORRIDOR WHERE THE BEST DYNAMICS WILL BE LOCATED.

THE UPPER LEVEL TROUGH WILL PUSH EAST OF THE REGION LATE MONDAY
AND INTO TUESDAY OF NEXT WEEK RESULTING IN BROAD NORTHWEST FLOW
ALOFT AND COOL TEMPERATURES. MAINLY DRY CONDITIONS ARE EXPECTED
INTO THE MIDDLE OF NEXT WEEK WITH HIGH TEMPERATURES INCREASING TO
NEAR NORMAL...AND GENERALLY IN THE 50S AND LOW 60S. THE ONLY MINOR
CONCERN IS SOME MODEL DISAGREEMENT WITH A RELATIVELY STRONG COLD
FRONT ON WEDNESDAY. THE GEM IS THE ONLY MODEL INDICATING A BACK
DOOR COLD FRONT PUSHING SOUTH THROUGH THE AREA ON
WEDNESDAY...WHICH WILL RESULT IN TEMPERATURES 10 TO 15 DEGREES
COOLER THAN OUR CURRENT FORECAST INDICATES. HOWEVER...THE GEM
CONTINUES TO BE THE OUTLIER SO WILL NOT ADJUST THE FORECAST FOR
WEDNESDAY TOO MUCH AT THIS TIME.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1147 AM MDT FRI OCT 31 2014

SHALLOW LOW CLOUD DECK HAS NEARLY ERODED OVER THE NEBRASKA
PANHANDLE...AND EXPECT VFR CATEGORY AT ALL FORECAST SITES ACROSS
SOUTHEAST WYOMING AND THE WESTERN NEBRASKA PANHANDLE OVER THE NEXT
24 HOURS. THE SURFACE HIGH PRESSURE RIDGE SHOULD CONTINUE RAPIDLY
SHIFTING EAST THROUGH TONIGHT WITH SOME LEE SIDE TROUGHING EXPECTED
EAST OF THE LARAMIE RANGE THROUGH TOMORROW MORNING. WE SHOULD SEE
RATHER BREEZY SOUTHERLY WINDS CONTINUE THROUGH EARLY EVENING FOR
CHEYENNE...AND THE WESTERN NEBRASKA FORECAST SITES...DIMINISHING A
BIT BY LATE EVENING AS THE LEE SIDE TROUGH BECOMES BETTER
ESTABLISHED RELAXING THE GRADIENT.

&&

.FIRE WEATHER...
ISSUED AT 352 AM MDT FRI OCT 31 2014

ALTHOUGH A DRY DAY...A CLOUDY OR FOGGY START IN MANY AREAS EAST
OF THE LARAMIE RANGE THIS MORNING. THIS WILL BE SLOW TO LIFT AND
BURN OFF...LIKELY NOT UNTIL LATE THIS MORNING OR AROUND MIDDAY.
WINDS WILL BE BREEZY WITH GUSTS OF 30 TO 40 MPH COMMON ACROSS MUCH
OF THE AREA. HUMIDITIES WILL FALL INTO THE UPPER TEENS OVER
CARBON/ALBANY COUNTIES THIS AFTERNOON. SATURDAY WILL OFFER THE
WARMEST DAY WITH HIGHS RISING INTO THE 60S TO LOW 70S OVER MUCH OF
THE SOUTHEAST WYOMING PLAINS. THE NEXT SYSTEM WILL BRING COOLER
TEMPERATURES ALONG WITH COOLER TEMPERATURES BY LATE SUNDAY AND
ESPECIALLY ON MONDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...WIND ADVISORY UNTIL 7 PM MDT THIS EVENING FOR NEZ002-003-095-096.

&&

$$

SHORT TERM...CAH
LONG TERM...TJT
AVIATION...JG
FIRE WEATHER...CAH



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