Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 170443
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1043 PM MDT SAT AUG 16 2014

.UPDATE...
ISSUED AT 919 PM MDT SAT AUG 16 2014

CONVECTION EARLIER THIS EVENING HAS DIED OUT WITH CLEAR SKIES OVER
MOST OF THE FORECAST AREA AT THIS TIME. THE ONLY CONCERN FOR LATER
TONIGHT IS THE OUTSIDE CHANCE OF A FEW THUNDERSTORMS IN THE
NORTHERN NEBRASKA PANHANDLE. MODELS DO SHOW THE LOW LEVEL JET
INCREASING TOWARDS MIDNIGHT WITH THE NOSE OF THE JET OVER THE
NORTHERN NEBRASKA PANHANDLE. AT THE SAME TIME THERE WILL BE AROUND
1000 J/KG OF CAPE IN PLACE. THE QUESTION IS IF THERE IS ENOUGH
CONVERGENCE ALONG THE NOSE OF THE JET TO BREAK THROUGH THE MID
LEVEL CAP TO DEVELOP CONVECTION. DID NOT MENTION ANY
THUNDERSTORMS IN THE FORECAST TONIGHT BUT THE POTENTIAL IS THERE
EVEN IF IT IS VERY SMALL. SHOULD STORMS DEVELOP THE EFFECTIVE
SHEAR IS LOW ENOUGH THAT SEVERE STORMS WOULD BE VERY UNLIKELY.

RED FLAG WARNING HAS BEEN ISSUED FOR MUCH OF SOUTHEAST WYOMING
SUNDAY AFTERNOON. WIND GUSTS OF 25 TO 30 MPH ALONG WITH RELATIVE
HUMIDITY VALUES IN THE LOW TEENS AND UPPER SINGLE DIGITS WILL
PRODUCE THE POTENTIAL FOR RAPID FIRE SPREAD.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 245 PM MDT SAT AUG 16 2014

A FEW SHOWERS AND STORMS HAVE FIRED THIS AFTERNOON OVER THE
CENTRAL NEB PANHANDLE ALONG A WEAK BOUNDARY. THESE SHOULD DIE OFF
LATE THIS AFTERNOON OR EARLY EVENING LEAVING MAINLY CLEAR SKIES
ACROSS THE CWA FOR OVERNIGHT INTO SUNDAY MORNING.

AN UPPER SHORTWAVE WILL PASS ACROSS MAINLY THE NORTHERN PLAINS
SUNDAY WITH A SFC TROF PROGRESSING EAST ACROSS THE PANHANDLE. THIS
WILL SET UP A WARM AND DRY DOWNSLOPE PATTERN ACROSS THE CWA SO
EXPECT MAINLY DRY WEATHER DURING THE DAY AS THE TROF SHOULD BE
EAST OF THE CWA BY EARLY AFTERNOON. A FEW BREEZY AREAS POSSIBLE
AROUND THE MOUNTAINS SUNDAY AFTERNOON. A WEAK SFC HIGH WILL THEN
BUILD SE ACROSS THE CWA SUNDAY NIGHT INTO MONDAY BRINGING A LITTLE
COOLER AIR. SFC UPSLOPE FLOW MONDAY MAY TRANSPORT ENOUGH MOISTURE
WESTWARD TO ALLOW FOR SOME ISOLATED CONVECTION MAINLY OVER THE
MTNS MONDAY AFTERNOON WITH ANY ACTIVITY THEN DISSIPATING EARLY IN
THE EVENING.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 330 PM MDT SAT AUG 16 2014

GENERAL CONSENSUS WITH THE 12Z/18Z MEDIUM RANGE MODEL GUIDANCE LEADS
TO BETTER THAN AVERAGE FORECAST CONFIDENCE. BOTH THE GFS AND ECMWF
PROG THE NEXT SHORTWAVE TO TRACK NORTHEAST ACROSS NORTHERN CO AND
SOUTHERN WY TUESDAY THEN EAST INTO THE CENTRAL PLAINS TUESDAY NIGHT.
A WEAKER TRAILING SHORTWAVE LOOKS TO MOVE ACROSS SOUTHEAST WY ON
WEDNESDAY. SUBTROPICAL MOISTURE WITH THESE PASSING WAVES WILL NOT
BE AS ROBUST AS LAST WEEK WITH PRECIP WATER VALUES LESS THAN AN
INCH. CONSEQUIENTYLY...SHOWER/TSTORM COVERAGE WILL BE ISOLATED TO
WIDELY SCATTERED.

FOR THE LATTER HALF OF THE WEEK...A SERIES OF SHORTWAVES WILL CARVE
OUT A LONG WAVE TROUGH OVER THE INTERMOUNTAIN WEST. MEANWHILE...A
UPPER RIDGE WILL AMPLIFY OVER THE EASTERN GREAT PLAINS AND MIDWEST.
THE FLOW ALOFT WILL PREVAIL FROM THE SOUTHWEST. SHORTWAVE ENERGY
WILL DISPLACED WELL NORTH AND WEST OF THE CWA. DIURNAL CONVECTIVE
COVERAGE WILL BE ISOLATED AND CONFINED TO THE HIGHER TERRAIN OF
SOUTHEAST WY. FAVORED THE DRIER GFS OVER THE WETTER ECWMF WITH
POPS AND QPF. WITH SHORTWAVES PASSING WELL NORTH OF THE CWA...THIS
WILL ENHANCE THE MID LEVEL GRADIENTS TO GENERATE GUSTY SOUTHWEST
SURFACE WINDS ALONG AND WEST OF THE LARAMIE RANGE. THE COMBINATION
OF GUSTY WINDS AND LOW HUMIDITY WILL RAISE THE FIRE SPREAD
POTENTIAL THERE.

700MB TEMPERATURES WILL CHANGE LITTLE TUESDAY THROUGH FRIDAY...RANGING
FROM 12C TO 15C. THE RESULT WILL BE ABOVE SEASONAL NORMAL TEMPERATURES
WITH DAYTIME HIGHS 85 TO 95 LOWER ELEVATIONS WITH 60S AND 70S MOUNTAINS.
SLIGHTLY COOLER TEMPERATURES CAN BE EXPECTED SATURDAY...ESPECIALLY
OVER SOUTHEAST WY. NIGHTTIME LOWS WILL BE IN THE 50S TO AROUND 60
WITH 40S MOUNTAINS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY EVENING)
ISSUED AT 1043 PM MDT SAT AUG 16 2014

VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD. MORE SHALLOW CU
DEVELOPMENT EXPECTED AGAIN SUNDAY AFTERNOON...WITH WINDS AGAIN
BECOMING BREEZY DURING THE AFTERNOON HOURS. NORTHWEST WINDS WILL
GUST TO 20-25 KNOTS AT SE WYOMING TERMINALS.

&&

.FIRE WEATHER...
ISSUED AT 925 PM MDT SAT AUG 16 2014
RED FLAG WARNING HAS BEEN ISSUED FOR MUCH OF SOUTHEAST WYOMING
SUNDAY AFTERNOON. WIND GUSTS OF 25 TO 30 MPH ALONG WITH RELATIVE
HUMIDITY VALUES IN THE LOW TEENS AND UPPER SINGLE DIGITS WILL
PRODUCE THE POTENTIAL FOR RAPID FIRE SPREAD.

MINIMAL FIRE CONCERNS FOR MONDAY AND TUESDAY AS WINDS WILL BE ON
THE LIGHT SIDE.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING FROM NOON TO 7 PM MDT SUNDAY FOR WYZ301-303-304-
     306-308>310.

NE...NONE.

&&

$$

UPDATE...SML
SHORT TERM...RE
LONG TERM...JAMSKI
AVIATION...HAHN
FIRE WEATHER...SML




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