Littleton, CO and Vicinity Weather Forecasts and Advisories

Area Forecast Discussion (National Weather Service)

     



AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
235 PM MDT FRI JUL 30 2010

.SHORT TERM...THE ATMOSPHERE IS A BIT DRIER TODAY OVER NORTHERN
SECTIONS OF OUR CWA AS PW VALUES HAVE DROPPED ABOUT A QUARTER OF AN
INCH FROM THE PAST 18 HOURS. A WEAK SURGE OF HIGH PRESSURE AS
SHIFTED WINDS TO THE NORTHEAST THIS AFTERNOON AND LOCAL VAD
WINDS/PROFILERS INDICATE WEAK UPSLOPE FLOW UP TO AROUND MOUNTAIN TOP
LEVEL WITH A LIGHT WESTERLY FLOW ALOFT. DESPITE THE DRIER
AIR...WATER VAPOR IMAGERY SHOWING A WEAK WAVE ROTATING AROUND THE
HIGH ACROSS FAR NRN CO. THIS IS WHAT MAY BE CREATING THE STORM
DEVELOPMENT OVER THE PLAINS ALONG WITH HIGHER DEWPOINTS AND STRONGER
HEATING FURTHER EAST. THE NAM REALLY DRIED THINGS OUT THRU THIS
EVENING WITH BARELY ANY QPF ON THE PLAINS WHILE THE GFS WAS QUITE
MOIST. A COMPROMISE IS IN ORDER AS THE AIRMASS IS NOT QUITE AS DRY
AS THE NAM SHOWS AND NOT NEARLY AS WET AS THE GFS. MOST OF THE
STORMS SO FAR ARE RATHER WEAK AS SFC BASED CAPES BELOW 1000J/KG AND
STORMS WILL CONTINUE TO BE "PULSY" IN NATURE. GIVEN THE DEEPENING
NERN FLOW...STORM MOTIONS WILL TO THE S-SW SO NOT EXPECTING STORMS
TO DO THE TRADITIONAL WEST TO EAST MOVEMENT. THE EXCEPTION WOULD BE
NEAR THE WYOMING BORDER AS THE W-NW FLOW ALOFT IS A BIT STRONGER.

AS FOR THE FLASH FLOOD WATCH...WE WILL LET THIS RIDE THE COURSE.
MOISTURE LEVELS ARE THE HIGHEST IN THE WATCH AREA SO THERE IS THE
POTENTIAL FOR FLASH FLOODING. HOWEVER...GIVEN THE AM CLOUD
COVER...SURFACE BASED CAPES ARE UNDER 800J/KG RESULTING IN MARGINAL
STORM STRENGTH. HIGH ENOUGH STORM MOTIONS AND OVERALL MARGINAL CAPES
MAY BE ENOUGH TO PREVENT ANY WIDESPREAD FLASH FLOODING AND ANY
FLOODING WOULD BE RATHER LOCAL IN NATURE. THE STRONGER STORMS ARE
ACTUALLY OCCURRING FURTHER NORTH WHERE WE HAD MORE HEATING TODAY.

FOR SATURDAY...LOW LVL FLOW WILL SHIFT MORE SOUTHEASTERLY OVER THE
NORTHEAST PLAINS BY SATURDAY AFTERNOON WHICH WILL HELP TO KEEP LOW
LVL MOISTURE PLENTIFUL WHILE PW VALUES INCREASE AGAIN OVER NORTHERN
SECTIONS. AGAIN A LACK OF ANY STRONG WAVE ALOFT AND ONLY MODEST
CAPES WILL KEEP CONVECTION AT A MANAGEABLE LEVEL. ANY FLOOD THREAT
ON SATURDAY LOOKS MINIMAL AS STORM MOTIONS SHOULD BE JUST FAST
ENOUGH TO PREVENT ANY WIDESPREAD FLOODING PROBLEMS. ANY FLASH
FLOODING WOULD BE MORE LOCALIZED AND OVER PROBLEM AREAS LIKE PAST
BURN AREAS.

.LONG TERM...SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH
SATURDAY EVENING AND POSSIBLY PAST MIDNIGHT AS A SHORTWAVE PASSES
OVER THE STATE. THE UPPER LEVEL RIDGE WILL BE CENTERED OVER THE
TEXAS PANHANDLE SATURDAY THEN SLOWLY MOVE EAST SUNDAY ONLY TO RETURN
OVER TEXAS THROUGH THE MIDDLE OF NEXT WEEK. THIS WILL KEEP WEAK WEST
TO SOUTHWESTERLY FLOW ALOFT OVER NORTHERN COLORADO AND MONSOONAL
MOISTURE RISING UP AND OVER THE RIDGE. PRECIPITABLE WATER VALUES
WILL REMAIN OVER AN INCH FOR THE PLAINS AND AROUND 0.8 OVER THE
MOUNTAINS ON SUNDAY TO AID IN THUNDERSTORMS DEVELOPING ONCE AGAIN
OVER THE MOUNTAINS THEN MOVE OFF ONTO THE PLAINS AS A LEE TROUGH
FORMS. THESE THUNDERSTORMS WILL HAVE THE POTENTIAL FOR HEAVY RAINS
AGAIN WITH NO HAIL EXPECTED AS FREEZING LEVELS REMAIN ABOVE 16500
FT.  MAX TEMPERATURES ARE EXPECTED TO REMAIN SLIGHTLY ABOVE NORMAL.
EARLY MONDAY...ANOTHER SHORTWAVE IS EXPECTED TO PUSH A COOL FRONT
SOUTH OVER THE FORECAST AREA. THIS WILL HELP PROVIDE CONVERGENCE AND
INCREASE THE COVERAGE OF STORMS OVER THE PLAINS WHILE COOLING
MAXIMUM TEMPERATURES BACK NEAR NORMAL...IN THE UPPER 80S TO LOW 90S.
PRECIPITABLE WATER VALUES ARE EXPECTED TO INCREASE TO 1.5-2 INCHES
THIS DAY OVER THE PLAINS...HOWEVER STEERING WINDS ARE EXPECT TO
INCREASE AS WELL.  THIS WILL KEEP THE SAME FLOODING POTENTIAL AS
OVER THE WEEKEND.

STARTING TUESDAY...THE RIDGE STARTS FLATTENING OUT KEEPING THE NEAR
NORMAL TEMPERATURES OVER THE STATE ALONG WITH THE DIURNAL PATTERN OF
AFTERNOON AND EVENING CONVECTION. A NORTHWESTERN US SHORTWAVE WILL
PUSH A LITTLE FURTHER SOUTH THURSDAY TO START BRINGING IN DRIER AIR
FROM THE NORTH. PRECIPITABLE WATER VALUES ARE PROGGED TO DROP TO
0.5-0.75 INCHES OVER THE FORECAST AREA...HAVE DECREASED POPS TO
REFLECT THIS.

&&

.AVIATION...A TOUGH CALL TODAY ON WHETHER STORMS WILL PASS OVER THE
LOCAL TERMINALS. GIVEN THE STORM DEVELOPMENT NORTH AND EAST OF THE
LOCAL AIRPORTS AND POTENTIAL OUTFLOW BOUNDARIES CAN`T RULE OUT A
THUNDERSTORM OVER THE AIRPORTS WITH LOCAL HEAVY RAIN AND POSSIBLE
ILS APPROACHES AT DENVER. SURFACE WINDS WILL CONTINUE TO SHIFT TO
THE EAST AND SOUTHEAST THRU THIS EVENING BEFORE TURNING MORE
SOUTHERLY OVERNIGHT.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...FLASH FLOOD WATCH UNTIL 9 PM FOR
THE PALMER DIVIDE...SOUTHERN FOOTHILLS...PARK COUNTY AND THE
SOUTHERN MOUNTAINS. (ZONES 34..36..37..41)

$$

ENTREKIN/KRIEDERMAN