Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 131726
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1126 AM MDT SAT SEP 13 2014

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 148 AM MDT SAT SEP 13 2014

TODAY...TEMPERATURE AND DEWPOINT SPREADS ARE DOWN TO 1 TO 4 DEGREES
EARLY THIS MORNING ACROSS FAR SOUTHEAST WYOMING AND THE SOUTHERN
NEBRASKA PANHANDLE...SO WILL NEED TO WATCH FOR POSSIBLE LOW CLOUDS
AND AREAS OF FOG DEVELOPMENT.

POSITIVELY TILTED LOW AMPLITUDE SHORTWAVE TROUGH ALOFT MOVES ACROSS
THE DAKOTAS THIS AFTERNOON...SENDING A WEAK COLD FRONT INTO OUR
COUNTIES...WITH THE FRONT LOOKING DRY DUE TO MINIMAL LOW AND MID
LEVEL MOISTURE. SIGNIFICANT WARMING TREND TODAY VERSUS FRIDAY BASED
ON PROJECTED 700 MB TEMPERATURES AND THICKNESSES.

TONIGHT...WITH CYCLONIC FLOW ALOFT...WEAK UPWARD VERTICAL MOTION
INDICATED AT 700 MB AND MOISTENING LOW AND MID LEVELS...WILL NEED TO
WATCH FOR POSSIBILITY OF A FEW LATE NIGHT SHOWERS...THOUGH FOR NOW
WILL KEEP IT DRY.

SUNDAY...WEAK COLD FRONT AND COOLER AIRMASS WILL LIE ACROSS OUR
NORTHEAST COUNTIES...TEMPERING THE WARMING TREND...THOUGH WITH
PLENTY OF SUNSHINE AND A MODERATING AIRMASS...WARMING TREND WILL
CONTINUE ALONG AND WEST OF INTERSTATE 25.

SUNDAY NIGHT...NEXT SHORTWAVE TROUGH ALOFT MOVES ACROSS THE EASTERN
DAKOTAS...SENDING ANOTHER REINFORCING COLD FRONT ACROSS OUR COUNTIES
AND WE MAY SEE A FEW SHOWERS IF THERE IS ENOUGH LOW AND MID LEVEL
MOISTURE. COOL MOIST UPSLOPE AND INCREASING BOUNDARY LAYER MOISTURE
SUGGESTS AREAS OF FOG AFTER MIDNIGHT ACROSS THE SOUTHERN NEBRASKA
PANHANDLE.

MONDAY...RESIDUAL CLOUD COVER AND RETURN SOUTHERLY WINDS WILL TEMPER
THE WARMING TREND FROM CHEYENNE TO SIDNEY...THOUGH MOST OTHER
LOCATIONS WILL SEE A SLOW WARMING TREND FROM SUNDAY. CONTINUED DRY
WITH LIMITED LIFT DESPITE ADEQUATE LOW AND MID LEVEL MOISTURE.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 300 AM MDT SAT SEP 13 2014

FORECAST CHALLENGES IN THE LONG TERM DEAL WITH PRECIP CHANCES
TOWARDS THE END OF THE WEEK.

GFS AND ECMWF VERY SIMILAR MONDAY NIGHT WITH NORTHWEST FLOW OVER
THE CWFA AND RIDGE AXIS OVER WESTERN NEVADA THROUGH IDAHO. SHOULD
BE FAIRLY WARM OVERNIGHT WITH 700MB TEMPERATURES +8 TO +10C.
SHOULD SEE MID TO UPPER 40S AREA WIDE.

UPPER RIDGE SLOWLY MOVES EAST INTO WESTERN MONTANA THROUGH THE DAY
TUESDAY WITH CONTINUED WARM TEMPERATURES IN NORTHWEST FLOW. A DRY
AND SUNNY DAY WITH HIGHS IN THE MID 70S WEST OF THE LARAMIE RANGE
AND LOW TO MID 80S IN THE PANHANDLE.

START TO SEE SOME DIFFERENCES BETWEEN THE GFS AND ECMWF WEDNESDAY.
GFS REMAINS DRY...BUT THE ECMWF BEGINS TO BRING SOME MOISTURE BACK
INTO THE AREA FROM THE DESERT SOUTHWEST. HAS SHOWERS BREAKING OUT
ACROSS NORTHERN COLORADO AND ALONG THE WYOMING/COLORADO STATE LINE
WEDNESDAY AFTERNOON. FOR NOW...KEPT THE FORECAST DRY...BUT MAY
NEED TO INCLUDE SOME SHOWERS IF THE ECMWF CONTINUES TO SHOW THIS.

ECMWF VERY AGGRESSIVE WITH MONSOONAL MOISTURE THURSDAY AFTERNOON.
LOOKS LIKE IT MAY BE SEEING SOME CONVECTIVE FEEDBACK ISSUES IN THE
QPF FIELDS AS IT HAS WIDESPREAD MODERATE AMOUNTS OF QPF OVER
UTAH...WESTERN WYOMING AND WESTERN COLORADO THURSDAY AFTERNOON.
FOR THIS REASON...DECIDED TO HOLD OFF ON INCREASING POPS THURSDAY
AFTERNOON. GFS HAS THE CWFA DRY...PROBABLY CLOSER TO REALITY. BUT
THE GFS ALSO BEGINS TO SHOW A FAIRLY POTENT SHORTWAVE MOVING
NORTHEAST ACROSS SOUTHERN NEVADA INTO WESTERN UTAH THURSDAY
EVENING. A LITTLE SLOWER THAN THE ECMWF...BUT IS STARTING TO TREND
TOWARDS AGREEMENT.

BEGAN TO INCREASE POPS THURSDAY NIGHT INTO FRIDAY AS THAT
SHORTWAVE GETS CLOSER TO HOME. BY FRIDAY MORNING...THE GFS SHOWS
THE TROUGH NEAR CASPER. ECMWF SLIGHTLY FASTER WITH THIS
FEATURE...IT HAS THE SHORTWAVE ROUGHLY 80-100 MILES FURTHER EAST.
BOTH ARE FORECASTING FAIRLY WIDESPREAD SHOWERS OVER CARBON COUNTY
BY FRIDAY MORNING...SPREADING TO OUR EASTERN ZONES BY FRIDAY
AFTERNOON.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY MORNING)
ISSUED AT 1119 AM MDT SAT SEP 13 2014

MINIMAL AVIATION CONCERNS THROUGH THE TAF PERIOD. BREEZY
WEST WINDS THIS AFTERNOON OVER MUCH OF SOUTHEAST WYOMING WITH
LIGHT WINDS INTO THE NEBRASKA PANHANDLE. LIGHT WINDS ACROSS THE
FORECAST AREA TONIGHT THROUGH SUNDAY MORNING. VFR EXPECTED THROUGH
THE TAF PERIOD...ALTHOUGH PATCHY FOG POSSIBLE IN THE NEBRASKA
PANHANDLE LATE TONIGHT AND EARLY TOMORROW. ANY FOG WOULD RAPIDLY
BURN OFF AFTER SUNRISE SUNDAY.

&&

.FIRE WEATHER...
ISSUED AT 148 AM MDT SAT SEP 13 2014

MINIMAL CONCERNS DUE TO PROJECTED HUMIDITIES AND
WINDS THE NEXT SEVERAL DAYS.

&&

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

$$

SHORT TERM...RUBIN
LONG TERM...CLAYCOMB
AVIATION...SML
FIRE WEATHER...RUBIN





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