Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 251645
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1045 AM MDT SAT APR 25 2015

.UPDATE...
ISSUED AT 1045 AM MDT SAT APR 25 2015

FORECAST STILL ON TRACK FOR TODAY...WITH CONVECTION EXPECTED THIS
AFTERNOON. STILL EXPECTING STRONGER STORMS OVER THE EASTERN
PLAINS COMPARED TO CLOSER TO THE URBAN CORRIDOR...HOWEVER NOT SURE
IF SEVERE STRENGTH WILL OCCUR. DEFINITELY A POSSIBILITY TO SEE
GUSTY WINDS TO 40 MPH AND SMALL HAIL...ESPECIALLY ALONG AND EAST
OF A LINE FROM EASTERN WELD COUNTY DOWN TO LIMON.

AS FOR THE MOUNTAINS...WILL START TO SEE SHOWERS AND THUNDERSTORMS
INCREASING THROUGH THE DAY. SO FAR...SNOW LEVELS LOOK TO STAY
AROUND 9,500-10,000 FEET TODAY THEN LOWER TO 8500 FEET TONIGHT.
MOST OF THE PRECIPITATION WILL BE OF CONVECTIVE NATURE TODAY AND
TONIGHT...SO IN TERMS OF AMOUNTS...NOT CONSIDERING ANY HIGHLIGHT
DUE TO THE SPOTTY NATURE IT WILL HAVE. SOME LOCALIZED AREAS MAY
SEE 3 TO 6 INCHES WHERE OTHER SPOTS MAY SEE LESS THAN AN INCH.
LOOKING FURTHER...UPSLOPE DEVELOPS SUNDAY WITH COOLER TEMPERATURES
WHICH WILL LIKELY INCREASE SNOW AMOUNTS. HOWEVER THE SYSTEM MAY BE
TOO FAR SOUTH...BUT THE RECENT GFS JUST CAME IN COOLER WITH SNOW
LEVELS DOWN TO 7500 FEET. MAY NEED TO ISSUE A HIGHLIGHT FOR THE
FRONT RANGE MOUNTAINS AND POSSIBLY THE UPPER FOOTHILLS...BUT NEED
TO STILL EVALUATE SOME OF THE OTHER MODELS COMING IN.

&&

.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 18Z SUNDAY MORNING)
ISSUED AT 1045 AM MDT SAT APR 25 2015

CLOUDS WILL BEGIN INCREASING AS THIS WEEKENDS STORM APPROACHES.
EXPECT SHOWERS AND THUNDERSTORMS MOVING OFF THE HIGHER TERRAIN
AND ACROSS THE DENVER AREA AFTER 19Z. BEST TIME FOR SHOWERS AND
STORMS IN THE DENVER AREA WILL BE 20-00Z...THEN IT SEEMS AS HIGH
RES MODELS SHOW A BREAK IN ACTIVITY THROUGH 03Z...THEN ANOTHER
WAVE OF ACTIVITY THROUGH 06Z. 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. HARD TO
FORECAST RIGHT NOW IF IT WILL BE DRIZZLE OR RAIN SHOWERS
OVERNIGHT. RAIN IS EXPECTED TO INCREASE SUNDAY.

WIND DIRECTION IS VERY TRICKY TODAY AS WESTERLY WINDS ALOFT ARE
MIXING DOWN INTO THE FOOTHILLS...YET SOUTHERLY WINDS OVER THE
EASTERN PLAINS MAY CYCLONE AROUND THE AROUND THE AIRPORTS. MIX
THIS WITH THE EXPECTED CONVECTION THIS AFTERNOON AND FORECASTING
GETS DIFFICULT. OVERALL EXPECT WINDS TO GENERALLY TREND TOWARD A
NORTHERLY DIRECTION THIS AFTERNOON THEN EASTERLY TONIGHT THEN
SOUTHEASTERLY LATE TONIGHT INTO SUNDAY.

&&

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

$$

UPDATE...KRIEDERMAN
SHORT TERM...MEIER
LONG TERM...BAKER
AVIATION...KRIEDERMAN


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