FXUS65 KCYS 061758
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1158 AM MDT SAT SEP 6 2008
.UPDATE...GRIDDED FORECASTS FOR TODAY IN DECENT SHAPE THANKS TO
OUR MIDNIGHT SHIFT SHORT TERM METEOROLOGIST. BASED ON TRENDS IN
SATELLITE IMAGERY...SURFACE OBSERVATIONS AND NAM/GFS MODEL
PROGNOSTICATIONS HAVE MADE SOME FINE TUNING ADJUSTMENTS TO THIS
AFTERNOON FORECAST IN THE GRIDS AND ZONE FORECAST PRODUCT. RUBIN
&&
.AVIATION...VFR THIS AFTERNOON...EXCEPT FOR LOCALIZED MVFR IN
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. SHOWERS WILL BE MOST
NUMEROUS NORTH OF A RAWLINS TO SCOTTSBLUFF LINE. RUBIN
&&
.PREV DISCUSSION... /ISSUED 232 AM MDT SAT SEP 6 2008/
SHORT TERM...TODAY THROUGH SUNDAY NIGHT.
EARLY THIS MORNING...NUMEROUS RAIN SHOWERS AND THE POSSIBILITY
FOR AN ISOLATED THUNDERSTORM WILL CONTINUE TO BE PRESENT THROUGH
AROUND SUNRISE THIS MORNING ACROSS THE NEBRASKA PANHANDLE AND
EXTREME SOUTHEAST WYOMING. AREAS OF FOG WILL BE PRESENT ALONG
INTERSTATE 80 OVER THE SUMMIT BETWEEN CHEYENNE AND LARAMIE...AND
PATCHY FOG WILL BE POSSIBLE ELSEWHERE EAST OF THE LARAMIE RANGE.
TODAY...THE SHOWER ACTIVITY WILL CONTINUE TO BE PRESENT ACROSS
AREAS EAST OF THE LARAMIE RANGE BENEATH THE FAVORED LEFT-EXIT
REGION OF A STRONG JET STREAK IN NORTHWEST FLOW ALOFT. THIS SHORT-
WAVE DISTURBANCE WILL SHIFT EASTWARD TODAY...WITH THE BEST
CONDITIONS FOR LIFT ALSO MOVING EAST. HAVE REPRESENTED THIS BY
SHIFTING PRECIPITATION CHANCES NORTH AND EAST AND SLIGHTLY
DECREASING THESE DURING THE AFTERNOON. AS PRECIPITATION DECREASES
AND THE UPPER RIDGE SHIFTS EAST SLIGHTLY...TEMPERATURES WILL BE
MUCH WARMER AND CLOSER TO NORMAL THAN THOSE OBSERVED FRIDAY. A
SURFACE COLD FRONT WILL BEGIN TO MOVE SOUTH ACROSS THE AREA DURING
THE LATE AFTERNOON WITH GUSTY NORTH WINDS ACCOMPANYING THE FRONTAL
PASSAGE.
TONIGHT...THE PRECIPITATION WILL DISSIPATE ACROSS THE AREA AS THE
COLD FRONT CONTINUES TO MOVE THROUGH AND PRODUCE GUSTY NORTH
WINDS. WINDS WILL WEAKEN BEHIND THE FRONT DURING THE OVERNIGHT
HOURS. AREAS OF LOW STRATUS CLOUDS AND PATCHY FOG CAN AGAIN BE
EXPECTED TO FORM BY AROUND SUNRISE.
SUNDAY AND SUNDAY NIGHT...SLIGHTLY COOLER TEMPERATURES WILL BE
OBSERVED SUNDAY. YET ANOTHER REINFORCING COLD FRONT BEGINS TO
TAKE SHAPE OVER IDAHO AND WESTERN WYOMING SUNDAY AS A RESULT OF
THE ENERGY IN THE NORTHWEST FLOW ALOFT. SURFACE PRESSURE FALLS ARE
FORECAST TO OCCUR IN THIS AREA BENEATH THE RIGHT ENTRANCE REGION
TO ONE JET STREAK...COMBINED WITH THE LEFT EXIT REGION OF ANOTHER
JET STREAK MOVING SOUTH ACROSS EXTREME WESTERN MONTANA. THIS SET-
UP WILL INCREASE MOISTURE ADVECTION ON SOUTHEAST BOUNDARY LEVEL
FLOW INTO THE FORECAST AREA...AND THE COMBINATION OF THE SURFACE
FRONTAL BOUNDARY AND ENERGY ALOFT WILL CREATE FAVORABLE CONDITIONS
FOR A FAIRLY SIGNIFICANT RAINFALL EVENT EAST OF THE LARAMIE RANGE
SUNDAY NIGHT. WILL KEEP PRECIPITATION CHANCES BELOW LIKELY WORDING
WITH THIS FORECAST PACKAGE...BUT CONFIDENCE IS INCREASING FOR
PRECIPITATION DURING THIS PERIOD.
LONG TERM...MONDAY THROUGH FRIDAY.
ANY LINGERING SHOWERS WILL MOVE OUT OF THE CWA MONDAY MORNING AS
UPPER TROF EXITS THE REGION TO THE EAST. TEMPERATURES ON THE COOL
SIDE FOR MONDAY AS SFC HIGH MOVES ACROSS THE CENTRAL PLAINS. DRY
AND WARMER CONDITIONS WILL THEN RETURN FOR TUESDAY AND WEDNESDAY
AS RETURN FLOW SETS UP AT THE SURFACE AND HEIGHTS RISE OVER THE
REGION. NEXT UPPER TROF TO AFFECT THE AREA SHOULD MOVE ACROSS THE
NORTHERN ROCKIES INTO THE NORTHERN PLAINS WEDNESDAY AND THURSDAY.
NOT A LOT OF WEATHER EXPECTED AS THE SYSTEM WILL PASS WELL NORTH
OF THE CWA ALONG WITH THE BETTER DYNAMICS BUT SYSTEM WILL PUSH A
PACIFIC FRONT ACROSS THE CWA WEDS NIGHT BRINGING A LITTLE COOLER
AIR FOR THURSDAY. WARMER AGAIN FRIDAY AS UPPER RIDGING OVER THE
WESTERN CONUS SHIFTS EASTWARD TOWARD THE REGION.
AVIATION...
AREAS OF MVFR...WITH LOCALIZED IFR IN THE HEAVIEST RAIN
SHOWERS... WILL CONTINUE TO BE PRESENT EARLY THIS MORNING. LOW
CEILINGS WILL BEGIN TO RISE BY AROUND 15Z...WITH VFR CONDITIONS
EXPECTED THROUGH THE REST OF THE DAY. SUPPORT FOR SHOWERS WILL
SHIFT NORTHEAST TODAY WITH SHOWERS CONTINUING NORTHEAST OF A LINE
FROM NEAR KCPR TO KIBM. EXPECT PATCHY FOG AND LOW CEILINGS EAST
OF THE LARAMIE RANGE AGAIN SATURDAY NIGHT...CREATING AREAS OF
MVFR AND LOCALIZED IFR CONDITIONS.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
UPDATE/AVIATION UPDATE...RUBIN
SHORT TERM/AVIATION...CARPENTER
LONG TERM...RE
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