Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KCYS 231652
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
952 AM MST SUN NOV 23 2014

.SHORT TERM...(TODAY THROUGH MONDAY NIGHT)
ISSUED AT 300 PM MST SAT NOV 22 2014

TODAY...MOIST NORTHWEST FLOW ALOFT CONTINUES TODAY WITH A FEW WEAK
SHORTWAVE TROUGHS IN THE FLOW. COLD AIR ADVECTION IN EARNEST TODAY
WITH PLENTY OF LOW AND MID LEVEL MOISTURE BEING ADVECTED ACROSS THE
SNOWY AND SIERRA MADRE RANGES...PRODUCING WIDESPREAD LIGHT
SNOW...AND THUS WE WILL CONTINUE THE WINTER STORM WARNING THERE. FOR
THE WESTERN NEBRASKA PANHANDLE...PROGGED GRADIENTS SUGGEST WIND
ADVISORY CRITERIA FROM LATE THIS MORNING THROUGH THIS AFTERNOON.

TONIGHT...MOIST NORTHWEST FLOW ALOFT CONTINUES PRODUCING OROGRAPHIC
SNOW SHOWERE ACROSS THE MOUNTAINS.

MONDAY...PROGRESSIVE LOW AMPLITUDE POSITIVELY TILTED SHORTWAVE MOVES
ACROSS OUR COUNTIES ON NORTHWEST FLOW ALOFT. MODERATE TO HEAVY
OROGRAPHIC SNOWS WILL CONTINUE ACROSS THE SNOWY AND SIERRA MADRE
RANGES IN FLOW ALOFT...DRY ELSEWHERE...EXCEPT FOR ISOLATED SHOWERS
OVER THE PLAINS.

MONDAY NIGHT...FAST NORTHWEST FLOW ALOFT CONTINUES. DECENT SURFACE
LEE TROUGH EXPECTED TO SCOUR THE COLD AIR OUT TO OUR EAST.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 300 PM MST SAT NOV 22 2014

TUESDAY THROUGH SATURDAY...NORTH/NORTHWEST FLOW EARLY IN THE PERIOD
WILL FLATTEN AND BECOME MORE ZONAL BY THE END OF THE WEEK AND NEXT
WEEKEND. 00Z MEDIUM RANGE SOLUTIONS ARE SIMILAR AT LEAST FOR TUESDAY
AND WEDNESDAY...BUT CONTINUE THEIR MASSIVE DISCREPENCIES THEREAFTER.
MORE ON THAT LATER. LETS TALK ABOUT THE PART OF THE FORECAST THAT
CARRIES THE GREATEST CONFIDENCE...TUESDAY AND WEDNESDAY.
NORTH/NORTHWEST FLOW WILL BE IN PLACE WITH WITH THE NOSE OF AN 160+
KNOT H3 JET MOVING OVERHEAD. TIGHT LLVL PRESSURE/HEIGHT GRADIENT AND
PROGD H7 WINDS OF OF 60-70 KNOTS WILL MAKE TUESDAY ANOTHER WIND DAY.
WILL UNDOUBTEDLY NEED WIND HIGHLIGHTS IN TIME ON TUESDAY ESPECIALLY
IN WIND PRONE AREAS. WIND SPEEDS OUTSIDE OF THESE AREAS WILL DEPEND
ON THE AMOUNT OF LENTICULAR CLOUD COVER AND CORRESPONDING MIXING.
OROGRAPHIC SNOWS WILL BE A NEAR CERTAINTY ON TUESDAY AFTERNOON AS
MOISTURE ADVECTION COMBINES WITH ACCELERATING LLVL FLOW. ANOTHER 4
TO 8 INCHES OF SNOW WILL BE POSSIBLE OVR THE SNOWY AND SIERRA MADRES
TUESDAY AND TUESDAY NIGHT. WILL UNDOUBTEDLY NEED ANOTHER WINTER
HEADLINE OVR THE SNOWY/SIERRA MADRE RANGES TUESDAY AND TUESDAY
NIGHT. TUESDAY WILL BE ABOUT 5 DEGREES MORE MILD AS WELL. FLOW
BECOMES MORE NORTHWEST ON WEDNESDAY...AS THE JET TRANSLATES EAST AND
BEGINS FLATTENING. OROGRAPHIC SNOW WILL DIMINISH ON WEDNESDAY AS
MOISTURE/LIFT DEPART.

AND NOW FOR THE UNCERTAINTY THAT CONTINUES FOR THANKSGIVING. IF YOU
RECALL MODEL SOLUTIONS FROM 24 HOURS SHOWED A COOLER/WETTER GFS
COMPARED TO MILD AND DRY ECMWF. WELL TONIGHTS RUNS HAVE COMPLETELY
FLIP FLOPED. NOW THE ECMWF SHOWS THE ARCTIC AIR MASS BACKING IN
EARLY THURSDAY AND SNOW DEVELOPING THURSDAY NIGHT AND FRIDAY.
COMPARATIVELY...THE GFS IS DRY AND SIGNIFICANTLY WARMER THRU THE
PERIOD. TO ILLUSTRATE THE UNCERTAINTY FURTHER...GFS MOS FORECASTS A
HIGH TEMPERATURE OF 63F FOR THANKSGIVING...WHILE THE ECMWF PROGS
34F. NEEDLESS TO SAY FORECAST CONFIDENCE REMAINS UNUSUALLY LOW FOR
THANKSGIVING AND FRIDAY. FOR NOW HAVE STEERED THE FORECAST TOWARDS A
COMPROMISE OF THE TWO FOR THANKSGIVING AND KEPT THINGS DRY. IN
EITHER CASE...COLD AIR RETREATS FOR THE WEEKEND AS THE PATTERN
BECOMES MORE ZONAL. STAY TUNED OVER THE NEXT FEW DAYS AS THE MODELS
HOPEFULLY GET A BETTER HANDLE ON THE HOLIDAY TIME PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 948 AM MST SUN NOV 23 2014

LATEST HRRR FORECAST USED FOR THE 18Z TAFS. SOME CONCERN FOR SOME
CONVECTIVE SNOW SHOWERS FOR KRWL AND KLAR AS SEEN IN THE HRRR
SOLUTION. BUT THESE BANDS ARE VERY NARROW AND IT WOULD BE ALMOST
IMPOSSIBLE TO NAIL DOWN TIMING OF THESE BANDS. DO BELIEVE MOST OF
THE SNOW SHOWERS WILL STAY SOUTH OF KLAR AND KRWL THIS
AFTERNOON...SO KEPT LOWER CONDITIONS OUT OF THE TAFS FOR BOTH
SITES. WILL CONTINUE TO MONITOR.

&&

.FIRE WEATHER...
ISSUED AT 209 PM MST SAT NOV 22 2014

MINIMAL CONCERNS DUE TO PROJECTED HUMIDITIES AND WINDS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING UNTIL 5 PM MST MONDAY FOR WYZ112-114.

NE...WIND ADVISORY UNTIL 6 PM MST THIS EVENING FOR NEZ002-003-019>021-
     054-055-095-096.

&&

$$

SHORT TERM...RUBIN
LONG TERM...CAH
AVIATION...GCC
FIRE WEATHER...RUBIN


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.