340
FXUS65 KCYS 042058
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
258 PM MDT SAT JUL 4 2009
SHORT TERM...TONIGHT THROUGH MONDAY
MOST OF THE TSTMS THIS AFTERNOON HAVE BEEN ALONG AND SOUTH OF I-80
FROM KCYS TO KRWL BUT MORE RECENTLY THERE ARE A FEW MORE STORMS
FURTHER TO THE NORTH AND EAST. RATHER COOLISH TEMPS ARE KEEPING
INSTABILITY DOWN FROM YESTERDAY WITH GENERALLY -1 TO -3 LIFTED
INDICES OVER CWA. SO...DESPITE GOOD DIRECTIONAL WIND SHEAR AND
MOISTURE ALONG WITH UPPER DISTURBANCE MOVING THIS WAY OUT OF
NORTHERN UT AND SW WY...SEVERE TSTMS NOT VERY LIKELY FROM NOW INTO
THIS EVENING. THERE WILL BE AT LEAST A SCATTERED COVERAGE OF
WEAKER TSTMS THOUGH WITH LOWEST POPS CONFINED TO FAR EASTERN CWA.
A FEW SHOWERS AND SOME LOW CLOUDS MAY OCCUR OVER PARTS OF EASTERN
CWA LATE TONIGHT. ON SUNDAY...BETTER INSTABILITY AND DIRECTIONAL
WIND SHEAR OVER EASTERN CWA WILL COMBINE WITH SLIGHTLY INCREASING
NW FLOW ALOFT OVER SSE SURFACE WINDS. ANOTHER ROUND OF SCATTERED
AFTERNOON AND EVENING TSTMS CAN BE EXPECTED...ESPECIALLY OVER
EASTERN HALF OF CWA WITH A FEW SEVERE TSTMS POSSIBLE. UPPER RIDGE
OVER WESTERN WY SUNDAY AFTERNOON WILL FINALLY SHIFT OVER OUR CWA
ON MONDAY FOR A DRIER AND WARMER DAY. NAM SHOWS SOME QPF IN THE
AFTERNOON WHILE GFS DOES NOT...SO DID KEEP A LOW POP FOR TSTMS.
LONG TERM...MONDAY NIGHT THROUGH FRIDAY
A SLIGHT CHANCE OF THUNDERSTORMS IS EXPECTED TO CONTINUE THROUGH
EARLY MONDAY EVENING. HOWEVER...STORMS ARE ANTICIPATED TO BE RATHER
WEAK. BOTH THE ECMWF AND NAM INDICATED SHOWERS LINGERING INTO THE
LATE EVENING...BUT THE GFS DOES NOT INDICATE ANY PRECIPITATION.
HAVE DECIDED TO AT LEAST MENTION A SLIGHT CHANCE AND DECREASE
THUNDERSTORMS QUICKLY BEFORE MIDNIGHT. THE RIDGE OF HIGH PRESSURE
CONTINUES TO SLIDE EASTWARD OVER THE AREA. THIS WILL ALLOW FOR
RATHER WARM TEMPERATURES ACROSS SOUTHEAST WYOMING AND THE NEBRASKA
PANHANDLE. ALTHOUGH TEMPERATURES WILL BE NEARLY 8 TO 10F DEGREES
ABOVE NORMAL...THEY WILL STILL BE NEARLY 10F DEGREES BELOW RECORD
HIGHS. TEMPERATURES ON TUESDAY WILL BE IN THE UPPER 80S TO MID
90S. SHOULD EXPECT TO SEE CHANCES OF THUNDERSTORMS DECREASING WITH
THE HIGH PRESSURE WITH LACK OF MOISTURE. HOWEVER...THE NAM IS
INDICATING SOME THUNDERSTORMS DEVELOPING LATE IN THE AFTERNOON ON
TUESDAY AND QUICKLY FADING. HOWEVER...WITH THE RIDGE WILL KEEP ANY
CHANCES OF THUNDERSTORMS AT A MINIMUM ON TUESDAY AND WEDNESDAY.
WEDNESDAY WILL BE THE WARMEST DAY THROUGH THE EXTENDED PERIOD WITH
HIGH TEMPERATURES REACHING UP TO 90S FOR AREAS EAST OF INTERSTATE
25 AND IN THE MID 80S FOR AREAS WEST OF INTERSTATE 25. AS THE
RIDGE IS SLOWLY DEPARTING OVER WYOMING AND THE NEBRASKA PANHANDLE
A SURFACE HIGH PRESSURE BUILDS OVER NORTHEAST COLORADO WITH THE
SURFACE LOW SLIDES ACROSS SOUTH DAKOTA. THE TIGHTENING OF THE
PRESSURE GRADIENT WILL ALLOW FOR BREEZY SOUTHWEST TO WESTERLY
WINDS ACROSS SOUTHEAST WYOMING. SO...IT WILL BE ARE WARM BREEZY
DAY ON WEDNESDAY. CERTAINLY THERE ARE SOME DIFFERENCES BETWEEN THE
ECMWF AND GFS...WITH THE ECMWF MUCH QUICKER MOVING THE UPPER LEVEL
RIDGE EASTWARD AND HAVING THE UPPER LEVEL LOW OVER MONTANA. IN
EITHER MODEL THE RIDGE WILL GET FLATTENED AND TEMPERATURES BE
SLIGHTLY COOLER BY THURSDAY AND FRIDAY. CHANCES OF PRECIPITATION
WILL INCREASE BY THE END OF NEXT WEEK.
AVIATION
SOME MVFR AND EVEN LOCAL IFR CEILINGS AND VSBYS WILL LIKELY OCCUR
AGAIN LATE TONIGHT AND PERSIST THROUGH MID MORNING SUNDAY OVER
NEBRASKA PANHANDLE. A SCATTERED COVERAGE OF THUNDERSTORMS WILL BE
OVER CWA INTO THIS EVENING AND OVER MUCH OF CWA SUNDAY AFTERNOON
AND EVENING WITH A FEW STRONG STORMS BRIEFLY CAUSING MVFR CEILINGS
AND VISIBILITIES IN RAIN. OTHERWISE...VFR CONDITIONS ARE EXPECTED.
FIRE WEATHER
SLIGHTLY BELOW NORMAL TEMPS AND INCREASED HUMIDITIES WILL PERSIST
THROUGH SUNDAY ALONG WITH SCATTERED AFTERNOON AND EVENING TSTMS.
THE WEATHER PATTERN WILL BECOME WARMER AND DRIER STARTING ON MONDAY
WITH ABOVE NORMAL TEMPERATURES BY THE MID PART OF NEXT WEEK. THERE
WILL BE A MINIMUM OF LATE DAY STORM ACTIVITY FOR MOST OF NEXT
WEEK. MINIMUM RELATIVE HUMIDITIES WILL DROP TO 15 TO 20 PERCENT IN
THE WYOMING PART OF THE CWA DURING THAT TIME. CURRENT FUELS STATUS
INDICATES THAT FUELS HAVE BEEN DRYING AND THIS WILL CONTINUE FOR
NEXT WEEK WHICH WILL START TO INCREASE FIRE WEATHER CONCERNS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM/AVIATION...JLH
LONG TERM....MG
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