Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 161813
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1113 AM MST TUE DEC 16 2014

.UPDATE...
ISSUED AT 1018 AM MST TUE DEC 16 2014

OUR MIDNIGHT SHIFT TEAM HAD THE FOG WELL COVERED AT TORRINGTON...
SCOTTSBLUFF AND ALLIANCE...AND ALONG THE NORTH PLATTE RIVER
VALLEY. EVEN AT 10 AM...VISIBILITIES IN FOG WERE STILL ONLY
ONE QUARTER OF A MILE AT ALLIANCE...ONE HALF MILE AT SCOTTSBLUFF
AND OVER TWO MILES AT TORRINGTON. EXTENDED FOG FOR A FEW HOURS
IN OUR GRIDDED FORECASTS.

FOR OUR AFTERNOON FORECAST...NEGATIVELY TILTED SHORTWAVE TROUGH
ALOFT MOVES NORTHEAST ACROSS EASTERN IDAHO...NORTHERN UTAH AND
WESTERN WYOMING...WITH THE 12Z NAM SPREADING LIGHT SNOW ACROSS
MUCH OF CARBON AND ALBANY COUNTIES...THUS HAVE ADJUSTED OUR
POPS AND SNOW COVERAGE GRIDS THERE TO MATCH EXPECTED SNOW
COVERAGE. ALSO ADJUSTED OUR MAXIMUM TEMPERATURES THIS AFTERNOON
AS WITH CLOUD COVER AND SNOWFIELD...TEMPERATURES WILL STRUGGLE
TO CLIMB ABOVE FREEZING AT SOME LOCATIONS ESPECIALLY ALONG THE
NORTH PLATTE RIVER VALLEY. ADJUSTED DEWPOINTS AND CLOUD COVER TO
MATCH TRENDS.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY NIGHT)
ISSUED AT 330 AM MST TUE DEC 16 2014

CHILLY NIGHT ACROSS THE REGION ESPECIALLY FOR THOSE AREAS IN THE
SOUTHERN NEBRASKA PANHANDLE WHERE SKIES ARE CLEAR AND WIDESPREAD
SNOW IS ON THE GROUND. TEMPERATURES IN THE NORTHERN PANHANDLE ARE
ABOUT 10 DEGREES WARMER DUE TO THE LOW CLOUDS AND PATCHY FOG. ALSO
GETTING FOG IN THE NORTH PLATTE RIVER VALLEY FROM DOUGLAS TO
TORRINGTON WITH REALLY LIGHT WINDS. THE HRRR SUGGESTS THAT THE LOW
CLOUDS WILL BE QUITE PERSISTENT OVER THE PANHANDLE THROUGH LATE
MORNING. GENERALLY QUIET WEATHER OVER THE NEXT FEW DAYS WITH WEAK
SFC PRESSURE GRADIENTS AND A LACK OF IMPACTFUL WEATHER SYSTEMS.
THE MODELS SHOW A SHORTWAVE TROUGH MOVING FROM THE GREAT BASIN
INTO WESTERN WY THIS AFTN INTO TONIGHT. IR IMAGERY CURRENTLY SHOWS
QUITE A BIT OF MIDLVL MOISTURE STREAMING NORTHEASTWARD INTO
COLORADO. THIS MOISTURE WILL PUSH ACROSS THE REGION BY THIS AFTN.
INCREASED POPS A BIT FOR THE SIERRA MADRE AND SNOWY RANGES FOR THE
AFTN...HOWEVER ONLY EXPECTING A FEW INCHES AT MOST. HIGH
TEMPERATURES WILL BE AROUND NORMAL OVER THE NEXT FEW DAYS
(GENERALLY IN THE MID-TO-UPPER 30S)...WHICH MEANS THAT SNOW COVER
FROM THE RECENT STORM WILL BE SLOW TO MELT.

SYNOPTIC PATTERN DOES NOT CHANGE A WHOLE LOT THROUGH THURSDAY.
SIMILAR TO THE LAST FEW WEEKS...THE UPPER LEVEL JET WILL BE REMAIN
ACROSS THE SOUTHWESTERN UNITED STATES WITH WEAK FLOW ALOFT OVER
WY. NO WIND CONCERNS AS THE CAG-CPR GRADIENT NEVER GETS ABOVE 20
METERS. A SFC HIGH OVER THE NORTHERN PLAINS WILL MAINTAIN SOUTH TO
SOUTHEAST WINDS OVER THE NEBRASKA PANHANDLE THROUGH WED NIGHT. THE
NAM AND SREF SHOW THE POTENTIAL FOR LOW CLOUD FORMATION TONIGHT
AND MORE SO ON WED NIGHT. THE MODELS HAVE BEEN CONSISTENT AT
SHOWING MUCH OF THE MOISTURE AND DYNAMICS ASSOCIATED WITH AN UPPER
LEVEL WAVE REMAINING SOUTH OF THE CWA ON WED AND WED NIGHT. KEPT
SLIGHT CHANCE POPS OVER THE SIERRA MADRE AND SNOWY RANGES...WITH
THE BEST CHANCES OF SNOW OVER COLORADO.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 330 AM MST TUE DEC 16 2014

SEASONAL AND A RELATIVELY TRANQUIL PERIOD THROUGH THE UPCOMING
WEEKEND. WARMER AND BREEZY TO LOCALLY WINDY CONDITIONS RETURN
EARLY NEXT WEEK. PERSISTENT NORTHWEST FLOW WILL BE IN PLACE FRIDAY
THRU SUNDAY WITH PERIODIC EMBEDDED SHORTWAVES PASSING OVER THE
REGION. LIGHT MOUNTAIN SNOW WILL BE A POSSIBILITY THRU THE PERIOD
ALONG WITH PERIODIC BOUTS OF CLOUD-COVER ELSEWHERE...THICKEST NEAR
SHORTWAVE ENERGY. SEE LITTLE MOVEMENT IN TEMPERATURES DURING THIS
PERIOD AS WELL AS NORTHWEST FLOW KEEP ADVECTION NEUTRAL. SO HIGHS
IN THE LOW 30S WEST OF THE LARAMIE RANGE AND 30S TO NR 40 EAST CAN
BE EXPECTED.

WINDS WILL STRENGTHEN FOR MONDAY/TUESDAY AS THE NOSE OF 150+ KNOT H3
JET STREAK APPROACHES AND MOVES OVERHEAD. ALTHOUGH TIMING
DIFFERENCES EXIST IN WHEN THE LLVL GRADIENT IS THE STRONGEST...BOTH
ARE SIMILAR IN PROGGING 50-60 KNOTS AT H7 FOR MONDAY AND TUESDAY. IF
SUBSEQUENT MODEL OUTPUT CONTINUES...THIS WOULD BE ENOUGH FOR THE
POSSIBILITY OF THE NEXT HIGH WIND EVENT MAINLY FOR WIND PRONE
AREAS. CHANNELED VORT ENERGY WILL ALSO PROVIDE CHANCES FOR SNOW
SHOWERS MONDAY AND TUESDAY AS WELL. MODELS AGAIN HAVE TIMING
DIFFERENCES DURING THIS PERIOD...SO FOR NOW JUST INTRODUCED SOME
LIGHT SNOW CHANCES DURING THIS PERIOD. DOWNSLOPE COMPONENT WILL
BOOST HIGH TEMPS MONDAY/TUESDAY INTO THE MID/UPPER 30S WEST AND
LOW/MID 40S OUT ON THE ERN PLAINS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1113 AM MST TUE DEC 16 2014

FOG/LOW STRATUS PERSISTS MAINLY IN THE NORTH PLATTE RIVER VALLEY
AND NEAR KCDR THIS MORNING...WITH VFR CONDITIONS ELSEWHERE. LIFTED
CIGS/VSBYS AROUND 20/21Z FOR THESE SITES ALTHO NOT CONFIDENT
CONDITIONS WILL IMPROVE MUCH BEFORE DROPPING ONCE AGAIN LATER THIS
EVENING. STILL EXPECT -SHSN EARLY THIS AFTERNOON AT THE WYO
SITES...WITH IFR CIGS/VSBYS EXPECTED AT KRWL IN MOIST SOUTHEAST
FLOW AFTER 05Z THIS EVENING. WINDS OVERALL WILL REMAIN RELATIVELY
LIGHT...EXCEPT NEAR KRWL WHERE GUSTS OF 20 TO 25 KTS ARE POSSIBLE
THIS AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 330 AM MST TUE DEC 16 2014

NO FIRE WEATHER CONCERNS OVER THE NEXT FEW DAYS.  COLD TEMPERATURES
WILL KEEP SNOW COVER ON THE GROUND ACROSS MUCH OF THE REGION.
AFTERNOON HUMIDITY VALUES WILL GENERALLY BE ABOVE 50 PERCENT AND
WINDS WILL BE LIGHT.

&&

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

$$

UPDATE...RUBIN
SHORT TERM...ZF
LONG TERM...CAH
AVIATION...RJM
FIRE WEATHER...ZF


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