Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 241819
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1219 PM MDT SUN AUG 24 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 331 AM MDT SUN AUG 24 2014

SATELLITE PIX THIS MORNING SHOWS WELL-DEFINED LOW PRESSURE AREA
EXHIBITING THE EARLY SIGNS OF OCCLUSION AS IT SPINS OVR SE
MONTANA. ALTHO MUCH OF THE AREA OVR THE CENTRAL ROCKIES IS DRY-
SLOTTED... THERE IS A SOME MOISTURE LIFTING NORTHEAST ACROSS
COLORADO ASSOCIATED WITH JET ENERGY. THIS JET STREAK COMBINED WITH
PBL MIXING UP TO AROUND 675MB WILL BE RESPONSIBLE FOR SURFACING 25
TO 35 MPH WIND GUSTS OVR SE WYOMING THIS AFTERNOON. OTHERWISE...
EXPECT A DRY DAY AHEAD AS MOISTURE WILL STAY BOTH NORTH AND SOUTH.
THIS WILL BEGIN CHANGING TONIGHT THO...AS THE JET STREAK SHIFTS
NORTH AND INTERACTS WITH E-W ORIENTED BOUNDARY THAT WILL BASICALLY
BISECT THE CWFA. SHOWER/WK THUNDERSTORM CHANCES LIFT NORTH ACROSS
THE AREA BEGINNING THIS EVENING...AND ESPECIALLY TONIGHT. SHOULD
SEE A BIT OF A LULL IN PRECIP MONDAY MORNING...HOWEVER BY AFTN THE
BOUNDARY BECOMES MORE N-S ORIENTED ALONG THE LARAMIE RANGE AS THE
SFC HIGH MOVES THRU THE NRN PLAINS. THIS WILL SET UP A FAVORABLE
AREA OF LLVL CONVERGENCE ALONG THE FRONT RANGE MONDAY AFTERNOON
AND EVENING. BEST RIBBON OF INSTABILITY HAS BACKED FURTHER WEST
COMPARED TO MODEL OUTPUT 24 HOURS AGO...NOW MOSTLY OVR THE SE
WYOMING PLAINS. PROGD SOUNDINGS SHOW STOUT CAP IN PLACE EAST. SO
HAVE TARGETED BEST THUNDERSTORM CHANCES HERE. BEST PRECIP CHANCES
WILL LIFT NORTHEAST MONDAY EVENING AS CONVECTION BECOMES ELEVATED.
PROGD PWATS OF AN INCH AND A QUARTER WILL FURTHER AID PRECIP
EFFICIENCY. AM NOT CONFIDENT ON THE EXTENT OF THE NOCTURNAL
CONVECTION MONDAY NIGHT...SO HAVE LEANED ON CHANCE POPS FOR NOW.
FLOW WILL CONTINUE TO AMPLIFY MON NT AND EARLY TUE AS UPSTREAM
TROUGH REACHES THE GREAT BASIN. TROUGH REACHES WYOMING TUESDAY...
SO EXPECT ANOTHER ROUND OF PRIMARILY AFTERNOON SHOWERS AND
THUNDERSTORMS. MODELS AGAIN ADVERTISE RIBBON OF INSTABILITY
AMPLIFYING AGAIN ALONG THE ERN PLAINS. DEEP LAYER SHEAR OF 40-50
KNOTS POINTS TO AT LEAST THE POTENTIAL FOR A FEW STORMS TO BECOME
STRONG TO LOCALLY SEVERE BOTH MON AND TUE. TEMPS WILL WARM WEST OF
THE LARAMIE RANGE THRU THE PERIOD...BUT COOL SLIGHTLY OVR THE ERN
PLAINS AS THE BOUNDARY BANKS UP AGAINST THE LARAMIE RANGE. IT WILL
ONLY BE A FEW DEGREES EITHER WAY...SO HIGHS WILL GENERALLY BE IN
THE 70S THRU TUESDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 331 AM MDT SUN AUG 24 2014

MAIN DIFFICULTY THIS PERIOD WILL BE DETERMINING THE DEPARTURE OF
THE UPPER SYSTEM THAT WILL BE AFFECTING THE AREA AT LEAST EARLY IN
THE PERIOD. GFS REMAINS MOST PROGRESSIVE WITH ADVANCING THE UPPER
TROF EAST OF THE AREA WEDS MORNING BRINGING AN END TO PCPN AT THAT
TIME WHILE THE EC REMAINS CONSISTENT IN A SLOWER MOVING CUT-OFF
UPPER SYSTEM THAT SLOWLY MOVES ACROSS THE REGION AND DOES NOT EXIT
UNTIL THURSDAY NIGHT. MOST GUIDANCES FAVOR A SOMEWHAT SLOWER
SOLUTION AND WILL CONTINUE WITH THAT IDEA HERE. AS A RESULT MILD
TEMPS WILL HOLD THROUGH WEDS INTO THURSDAY WITH AT LEAST SCTD
SHOWERS AND A FEW TSTMS MAINLY WEDS AND WEDS NIGHT. ACTIVITY
SHOULD BECOME MORE ISOLATED THURSDAY AND MAINLY EAST OF THE MTNS
BEFORE MAINLY DRY WEATHER SETS IN FOR FRIDAY AND SATURDAY ALONG
WITH WARMER TEMPS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 1219 PM MDT SUN AUG 24 2014

VFR CONDITIONS ARE EXPECTED THRU THE TAF PERIOD. GUSTY SOUTHWEST
WINDS OF 25 TO 30 KTS WILL CONTINUE THRU THE LATE AFTERNOON...AND
WILL SUBSIDE BETWEEN 23 AND 02Z. A COLD FRONT WILL DROP SOUTH OVER
THE PLAINS TONIGHT AND WILL STALL ALONG THE LARAMIE RANGE MONDAY
MORNING. WINDS WILL SWITCH TO THE NORTHEAST BEHIND THE
FRONT...WITH SHOWERS AND PERHAPS A FEW WEAK T-STORMS DEVELOPING
ALONG THE FRONT AS WELL.

&&

.FIRE WEATHER...
ISSUED AT 331 AM MDT SUN AUG 24 2014

FIRE WEATHER CONCERNS ARE EXPECTED TO BE MINIMAL THRU THE MIDDLE
OF THE WEEK. CONDITIONS WILL BE THE CLOSEST TO CRITICAL TODAY...AS
WIND GUSTS OF 25-35 MPH WILL BE COMMON ACROSS SE WYOMING. RELATIVE
HUMIDITIES WILL ONLY REACH INTO THE UPPER TEENS/LOW 20S HOWEVER.
MOISTURE CHANCES AND SLIGHTLY COOLER TEMPERATURES WILL RETURN FOR
MON-WED. DRIER AND WARMER CONDITIONS LOOK TO RETURN TOWARDS THE
END OF THE WEEK...WHICH MAY PROVIDE THE NEXT OPPORTUNITY TO SEE
CRITICAL CONDITIONS.

&&

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

$$

SHORT TERM...HAHN
LONG TERM...RE
AVIATION...RJM
FIRE WEATHER...HAHN






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