Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 011143
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
543 AM MDT WED JUL 1 2015

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 400 AM MDT WED JUL 1 2015

OVERNIGHT WATER VAPOR IMAGERY ANIMATION DEPICTED THE CENTER OF THE
UPPER RIDGE NEAR THE AZ/NV BORDER. SEVERAL CLUSTERS OF DEEP
CONVECTION ARE ROTATING CLOCKWISE AROUND THE PERIPHERY OF THE
CENTER. A SHORT WAVE TROUGH MOVING SOUTHEAST ACROSS SOUTHERN SD
AND NORTHERN NE PRODUCED ISOLATED TSTORM ACTIVITY. ANOTHER TROUGH
WAS MOVING EAST FROM SOUTHEAST BRITISH COLUMBIA INTO SOUTHWEST
ALBERTA. SKIES WERE PARTLY CLOUDY WITH LIGHT AND VARIABLE WINDS.
TEMPERATURES WERE IN THE 50S AND 60S.

SHORT RANGE MODEL RUNS HAVE BEEN CONSISTENT WITH THE WESTWARD
PROGRESSION OF THE UPPER RIDGE ACROSS THE GREAT BASIN THROUGH THE
END OF THE WEEK. OUR REGION WILL CONTINUE TO BE INFLUENCED BY A
ACTIVE NORTHWEST FLOW ALOFT FOR THE NEXT FEW DAYS AS SHORT WAVE
TROUGHS TREK SOUTHEAST FROM THE CANADIAN ROCKIES THROUGH THE
NORTHERN GREAT PLAINS AND MIDWEST.

A SURFACE FRONT EXTENDING FROM NORTHEAST WY INTO WESTERN NE WILL
ADVANCE WESTWARD INTO SOUTHEAST WY TODAY AS LOW PRESSURE MOVES
FROM WESTERN SD INTO SOUTH CENTRAL NE. THE FRONT WILL STALL NEAR
THE LARAMIE RANGE LATER TODAY. WEAK UPSLOPE FLOW...FRONTAL
CONVERGENCE AND PASSING UPPER LEVEL ENERGY WILL BE FOCI FOR
SCATTERED AFTERNOON AND NIGHTTIME CONVECTION. TSTORMS WILL
INITIATE ALONG AND WEST OF THE LARAMIE RANGE EARLY AFTERNOON THEN
MOVE EAST ONTO THE PLAINS BY LATE AFTERNOON. MODELS ARE PROGGING
35-45 KT SHEAR IN THE LOW/MID LEVELS WITH 50-70 KT UPPER LEVEL
WEST-NORTHWEST WINDS. SBCAPE VALUES ARE NOT THAT HIGH...GENERALLY
LESS THAN 1000 J/KG EAST OF THE LARAMIE RANGE. GIVEN THE MARGINAL
INSTABILITY...SHEAR MAY BE ENOUGH TO PRODUCE A FEW ORGANIZED
TSTORMS MAINLY CAPABLE OF WIND GUSTS IN EXCESS OF 58 MPH...SIMILAR
TO TUESDAY. IT WILL BE 5-10 DEGREES COOLER TODAY WITH HIGHS IN
THE 70S AND 80S.

THE SURFACE FRONT NEAR THE FRONT RANGE DRIFTS SOUTH INTO NORTHERN
COLORADO THURSDAY AS THE UPPER JET PUSHES SOUTHEAST INTO THE
CENTRAL PLAINS. STILL WEAK UPSLOPE AND INSTABILITY FOR AFTERNOON
AND EVENING CONVECTION...MAINLY FROM THE SOUTHEAST WY MOUNTAINS
EASTWARD INTO THE SOUTHERN NE PANHANDLE. HIGH TEMPERATURES WILL
BE ANOTHER 5 DEGREES COOLER THURSDAY FROM TODAY`S HIGHS.

UPPER RIDGE FORECAST TO HEAD EAST TOWARD THE FOUR CORNERS FRIDAY.
MODELS SHOW ANOTHER PIECE OF ENERGY ALOFT PASSING SOUTHEAST ACROSS
THE REGION IN THE AFTERNOON. TEMPERATURES ALOFT WARM SOMEWHAT
WHICH WILL CAP THE MAJORITY OF THE DIURNAL CONVECTION EXCEPT FOR
ISOLATED OROGRAPHICALLY-INDUCED TSTORMS OVER THE HIGHER TERRAIN.
HIGH TEMPERATURES WILL BE ABOUT 5 DEGREES WARMER FRIDAY.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 330 AM MDT WED JUL 1 2015

UPPER HIGH CENTER LOCATED NR THE 4-CORNERS WILL SUPPRESS CONVECTIVE
ACTIVITY AND MAINTAIN SEASONALLY WARM CONDITIONS FOR THE 4TH. THESE
RELATIVELY DRY WEATHER CONDITIONS APPEAR TO BE SHORT-LIVED
HOWEVER...AS THE LATEST GFS/ECMWF ADVERTISE THE NRN STREAM JET AND
ASSOCIATED SHORTWAVE ENERGY DIPPING SOUTH INTO THE NRN PLAINS FOR
SUNDAY AND MONDAY. A RELATIVELY STRONG SFC COLD FRONT WILL RACE
SOUTH ACROSS THE CWFA DURING THE DAY ON SUNDAY. DEPENDING ON
SUNDAY`S FROPA TIMING...SEVERE WEATHER MAY BE A CONCERN...ESPECIALLY
ACROSS THE SRN HALF OF THE NEBRASKA PANHANDLE. AS INSTABILITY
WANES SUNDAY NIGHT...PRECIP MODE BECOMES STRATIFORMED IN THE
MOIST UPSLOPING POST-FRONTAL AIR MASS UNLESS ELEVATED CONVECTION
IS SUSTAINABLE. FOR NOW...LOOKS TO BE A LOW CLOUD/FOG ALONG WITH
WIDESPREAD LIGHT RAIN EVENT. STILL A LONG WAYS OUT...BUT HAVE
STEERED RAIN CHANCES UP ACCORDINGLY. THE ERN PLAINS TURN MORE
STABLE ON MONDAY...BUT SHOULD STILL SEE INSTABILITY POOL ALONG AND
WEST OF THE STALLED FRONT ALONG THE LARAMIE RANGE. SO CONFINED THE
HIGHEST RAIN CHANCES ALONG AND WEST OF I-25. THE PATTERN WILL
REMAIN ACTIVE INTO TUESDAY AND ESPECIALLY WEDNESDAY AS RRQ OF THE
NRN STREAM JET REMAINS OVR THE AREA. WOULD NOT BE SURPRISED TO SEE
THE SEVERE WEATHER THREAT INCREASE TOWARDS THE MIDDLE OF NEXT
WEEK...ESPECIALLY ON WEDNESDAY. AFTER A WARM DAY ON SATURDAY...
TEMPERATURES WILL GRADUALLY FALL THRU MONDAY...WITH 70S EXPECTED
MOST LOCALES. THESE TEMPERATURES WILL WARM TUE-WED AS THE STALLED
FRONT WASHES OUT AND WAA RETURNS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 543 AM MDT WED JUL 1 2015

A QUIET START TO THIS TAF CYCLE WITH JUST A FEW-SCT120 CLOUD DECK
STREAM OVERHEAD. THIS WILL CHANGE AFTER 20Z FOR SOUTHEAST WYOMING
AIRPORTS AS SCATTERED -TSRAS DEVELOP. MAY SEE SOME BRIEF MVFR
CIGS/VSBYS IN INDIVIDUAL THUNDERSTORMS...THOUGH CONTINUED VCTS IN
TAFS GIVEN EXISTING TIMING/LOCATION UNCERTAINTIES. THIS ACTIVITY
WILL SPREAD TO WRN NEBRASKA SITES THIS EVENING AND THRU THE
OVERNIGHT HOURS. IN FACT...THERE ARE SOME INDICATORS THAT SUGGEST
-TSRAS WILL LINGER AFTER MIDNIGHT AT KCDR AND KAIA. FOR NOW HAVE
ADDED TO VCTS TO THESE SITES TO ACCOUNT FOR THESE EXPECTATIONS.

&&

.FIRE WEATHER...
ISSUED AT 330 AM MDT WED JUL 1 2015

NO FIRE WEATHER CONCERNS FOR THE NEXT FEW DAYS. FRONT STALLED
ALONG THE LARAMIE RANGE IN SOUTHEAST WYOMING COMBINED WITH WEAK
UPSLOPE AND PASSING UPPER LEVEL ENERGY WILL GENERATE SCATTERED
SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND TONIGHT. LOCALLY
HEAVY RAIN AND GUSTY WINDS WILL BE POSSIBLE WITH SOME OF THE
THUNDERSTORMS. THE FRONT DRIFTS SOUTH INTO NORTHERN COLORADO
THURSDAY WITH WIDELY SCATTERED AFTERNOON AND EVENING CONVECTION.
DRIER CONDITIONS ARE FORECAST FRIDAY AND SATURDAY... ESPECIALLY
WEST OF THE LARAMIE RANGE WHERE MINIMUM HUMIDITIES FALL TO 10 TO
15 PERCENT. WINDS WILL BE LIGHT...EXCEPT NEAR THUNDERSTORMS.

&&

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

&&

$$

SHORT TERM...MAJ
LONG TERM...CAH
AVIATION...CAH
FIRE WEATHER...MAJ


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