Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 251003
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
403 AM MDT SAT APR 25 2015

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 400 AM MDT SAT APR 25 2015

SHORT WAVE RIDGE OVER THE STATE AT THIS TIME WILL BE PUSHED EAST OF
THE AREA LATER TODAY AS UPPER LEVEL TROUGH DIGS SOUTHEAST OVER THE
WESTERN STATES. SOUTHWEST FLOW ALOFT WILL PREVAIL ACROSS COLORADO BY
AFTERNOON. PLENTY OF LIFT AND MOISTURE WITH THIS SYSTEM AS THERE ARE
SHOWERS OVER THE GREAT BASIN NOW. EXPECT THESE SHOWERS TO SHIFT
EASTWARD INTO WESTERN COLORADO THIS MORNING AND INTO THE CENTRAL
MOUNTAINS AROUND OR JUST AFTER 18Z. THE CLOUDS AND SHOWERS WILL
SPREAD EASTWARD OVER THE FRONT RANGE AND NEAR BY PLAINS THROUGH THE
AFTERNOON HOURS. AIRMASS WILL BECOME UNSTABLE WITH CAPES OF 500-1000
J/KG OVER THE EASTERN PLAINS. CAPES WILL BE LOWER NEAR THE
FOOTHILLS. COULD BE A MARGINALLY SEVERE STORM OR TWO WITH LARGE HAIL
AND WIND GUSTS TO 60 MPH. WILL HAVE 30-50 POPS ALONG THE FRONT RANGE
FOR THE SCATTERED CONVECTION. EXPECT A BETTER CHANCE FOR
PRECIPITATION OVER THE EASTERN PLAINS THIS EVENING DUE TO BETTER
INSTABILITY AND MOISTURE.

THE UPPER LEVEL TROUGH WILL DIG INTO NORTHERN ARIZONA BY 12Z SUNDAY.
FOR THE REST OF SATURDAY NIGHT...EXPECT SHOWERS TO DECREASE OVER THE
HIGHER TERRAIN AND ALONG THE FRONT RANGE...BUT SHOULD STILL BE
ENOUGH MOISTURE AROUND FOR ISOLATED TO SCATTERED SHOWERS. SHOWERS
AND STORMS MAY LINGER INTO THE OVERNIGHT HOURS OVER THE EASTERN
PLAINS...THUS WILL KEEP HIGHEST POPS OVER THIS AREA. A SURFACE LOW
PRESSURE TROUGH OVER WESTERN COLORADO AND A SURFACE HIGH OVER THE
NORTHERN U.S. WILL PRODUCE AN EASTERLY UPSLOPE FLOW LATE TONIGHT.
THIS WILL INCREASE LOW LEVEL MOISTURE. BY 12Z SUNDAY...EXPECT LOW
CLOUDS AND FOG DUE TO THIS WITH AREAS OF DRIZZLE AND RAIN.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 400 AM MDT SAT APR 25 2015

PRINCIPAL FOCUS WILL BE ON THE CLOSED LOW STORM SYSTEM
SWINGING SEWRD ACRS THE FOUR CORNERS REGION SUNDAY MORNING. THIS
STORM TRACK IS A BIT FARTHER SOUTH THAN WHAT PREVIOUS MODEL RUNS HAD
INDICATED. CONSEQUENTLY ITS SPHERE OF INFLUENCE HAS ALSO SHIFTED
SOUTH WHICH PLACES SERN COLORADO IN THE BEST POSITION FOR
SIGNIFICANT PRECIP THIS GO ROUND. TEMPERATURES ON SUNDAY ACRS N-
CNTRL AND NERN COLORADO DO NOT LOOK AS COLD EITHER. LATEST GUIDANCE
INDICATES NEARLY SATURATED BNDRY LAYER ENVIRONMENT EAST OF THE MTNS
SUNDAY MORNING AS SELY LOW-LEVEL FLOW CONTINUES TO ADVECT IN LOW-
LEVEL MOISTURE. FOR THAT REASON WILL ADD AREAS OF FOG UP ALONG THE
FRONT RANGE SUN MORNING. WILL ALSO HANG ONTO THE LIKELY POPS...BUT
PRECIP AMOUNTS RATES OF FALL SHOULD BE LIGHT AT THIS TIME. AS THIS
UPSLOPE DEEPENS...LAPSE RATES STEEPEN AS WELL WITH COOLING ALOFT.
00Z/06Z NAM RUNS INDICATE AREAS OF CAPE ON THE 600-1200 J/KG RANGE
OVER AND ALONG THE FRONT RANGE DURING THE LATE MORNING AND EARLY
AFTERNOON HRS ON SUNDAY. WITH THE WET BULB ZERO STILL UP AROUND
10000 FT MSL AT THAT TIME...PRECIP SHOULD FALL AS RAIN EXCEPT OVER
THE HIGHEST MTN PEAKS AND RIDGES. HAIL OR GRAUPEL ALSO A POSSIBILITY
WITH CBS BUILDING OVER THE FRONT RANGE FOOTHILLS. BELIEVE THE BULK
OF THE SHOWERY PRECIP ON SUNDAY WILL FALL ROUGHLY ALONG AND WEST OF
INTERSTATE 25 WITH THE GREATER PRECIP AMOUNTS WEST OF THE
CONTINENTAL DVD ACCORDING TO THE MODELS. TEMPERATURES ON SUN AS MUCH
AS 15-18 DEG F LOWER THAN THE DAY BEFORE DUE IN PART TO THE
ANTICIPATED EXTENSIVE CLOUD COVER.

SUNDAY NIGHT-MONDAY...MODELS SHOW THE CLOSED UPPER LOW TRACKING
SEWRD AT A SLIGHTLY FASTER PACE ACRS NORTHERN NEW MEXICO. MOST THE
UPWARD FORCING AND INSTABILITY WITH THIS STORM PASSES TO OUR SOUTH.
HOWEVER...EAST-NORTHEAST UPSLOPE WILL BE AT ITS STRONGEST DURING
THIS PERIOD WITH 15-25KT EAST-NORTHEASTERLY WINDS REACHING MTN TOP
LEVEL. EAST FACING MTN SLOPES ROUGHLY 8500 FT AND ABOVE ARE LIKELY
TO SEE ALL SNOW SUN NIGHT THRU MON MORNING...WITH A RAIN/SNOW MIX
LOWERING TO AROUND 7000 FT WITH COLDER AREA FILTERS DOWN FROM
WYOMING AS THE UPPER LOW TRACKS ACRS THE NRN TEXAS PANHANDLE. SNOW
TOTALS IN THE HIGH COUNTRY...ESPLY EAST FACING SLOPES BY MON
AFTERNOON COULD RANGE ANYWHERE FROM 5-15 INCHES. IT MAY BE NECESSARY
TO HOIST A WATCH OR ADVISORY SHOULD THESE AMOUNTS SHOW UP ON
THE NEXT MODEL RUN.

TUESDAY AND BEYOND...UPPER LOW MOVES OUT AND AN UPPER RIDGE BUILDS
IN FROM THE GREAT BASIN. THIS WILL RETURN DRY CONDITIONS AND NEAR TO
ABOVE AVERAGE TEMPERATURES TO THE REGION THROUGH FRIDAY.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 400 AM MDT SAT APR 25 2015

VFR CONDITIONS WILL PREVAIL WITH LIGHT WINDS THROUGH 18Z. CLOUDS
WILL INCREASE AFTER 18Z WITH SHOWERS AND THUNDERSTORMS MOVING OFF
THE HIGHER TERRAIN AND ACROSS THE DENVER AREA. BEST TIME FOR SHOWERS
AND STORMS IN THE DENVER AREA WILL BE 21-01Z. MAIN THREAT WILL BE
GUSTY OUTFLOW WINDS UP TO 40 KNOTS. CEILINGS WILL BRIEFLY FALL BELOW
6000 FEET UNDER THE STRONGER SHOWERS AND STORMS. EASTERLY WINDS WILL
TRANSPORT LOW LEVEL MOISTURE INTO THE AREA LATE TONIGHT...AFTER 06Z
SUNDAY. THIS WILL BRING LOW CLOUDS AND AREAS OF FOG. BY 12Z
SUNDAY...EXPECT CEILINGS WILL BE BELOW 1000 FEET WITH A GOOD CHANCE
OF FOG WITH VISIBILITY A HALF MILE OR LOWER.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...MEIER
LONG TERM...BAKER
AVIATION...MEIER


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