Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 182111
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
311 PM MDT MON MAY 18 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 310 PM MDT MON MAY 18 2015

MAIN CONCERNS ARE HEAVY SNOW OVER THE MOUNTAINS AND POTENTIAL FOR
FLOODING ON THE NORTHEAST PLAINS. STRONG UPPER LOW OVER
CALIFORNIA WILL INTO UTAH ON TUESDAY WHILE STRONG ENERGY ROTATES
THROUGH COLORADO LATER TONIGHT AND TUESDAY. STRONG QG ASCENT OVER
AREA FROM MIDNIGHT THROUGH 18Z TUESDAY BEFORE SHIFTING INTO
NEBRASKA BY LATE TUESDAY AFTERNOON AND EVENING. SHOWERS WILL
DECREASE A BIT FROM SOUTHWEST TO NORTHEAST DURING TUESDAY
AFTERNOON. WILL HAVE CATEGORICAL POPS FOR MUCH OF THE AREA BY
MIDNIGHT TONIGHT. INCREASING SOUTHEAST WINDS TONIGHT WILL FAVOR
THE NORTHERN FRONT RANGE FOOTHILLS AND OVER THE CYS RIDGE. COULD
BE LESSER AMOUNTS NORTH OF THE PALMER DIVIDE THROUGH DENVER AND
ADJACENT POINTS TO THE EAST. LOOKS LIKE HEAVIEST SNOW WILL REMAIN
ABOVE 10000 FEET WITH SNOW LEVEL VARYING FROM 8000 TO 9500 FEET.
THERE WILL BE SOME SNOW ACCUMULATION IN THE HIGHER FOOTHILLS BUT
MOST LIKELY NOT ENOUGH FOR ANY HILITES.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 310 PM MDT MON MAY 18 2015

RAIN AND MOUNTAIN SNOW WILL CONTINUE TO DECREASE TUESDAY EVENING
AS UPPER SYSTEM LIFTS FURTHER OFF TO THE NORTHEAST. COULD SEE
ANOTHER INCH OR TWO IN THE NORTHERN MOUNTAINS AS OROGRAPHICS ARE
FAIR THERE. HOWEVER...LARGE SCALE SUBSIDENCE AND STABILIZATION
SHOULD BRING AN END TO MOST OF THE PRECIPITATION ON THE PLAINS DURING
THE COURSE OF THE EVENING. THERE IS A SLIGHT RISK OF A BIT OF SNOW
MIXED IN WITH THE RAIN OVER THE FAR NORTHERN BORDER AREA TOWARD
SIDNEY...BUT STRONGER WARM ADVECTION SHOULD BE ENOUGH TO BRING
ALMOST ALL RAIN.

ON WEDNESDAY...A FLAT UPPER LEVEL RIDGE WILL BUILD ACROSS
COLORADO. THE AIRMASS IS RATHER STABLE ON THE PLAINS SO MOST OF
THE INSTABILITY AND CONVECTION WILL HAVE TO FIRE OVER THE HIGH
COUNTRY DURING THE AFTERNOON...AND THEN SPREAD EAST ACROSS THE
FOOTHILLS AND PLAINS LATER IN THE DAY INTO THE EVENING HOURS.

ON THURSDAY...ANOTHER UPPER LEVEL TROUGH WILL MOVE INTO CALIFORNIA
WITH SOUTHWESTERLY FLOW DEVELOPING OVER THE AREA. AT THE
SURFACE...HIGH PRESSURE WILL CONTINUE TO AFFECT NORTHEAST
COLORADO WITH COOL SOUTHEAST LOW LEVEL FLOW. STILL THINK THE ECMWF
HAS A BETTER HANDLE ON HIGH TEMPS OVER NORTHEAST COLORADO WILL
KEEP READINGS MAINLY IN THE UPPER 50S TO LOWER 60S. AS FAR AS
PRECIP GOES...THE AIRMASS ACROSS THE PLAINS WILL REMAIN RATHER
STABLE WITH THE BEST INSTABILITY REMAINING OVER THE HIGHER
TERRAIN. THUS WILL KEEP THE BEST POPS OVER THE MOUNTAINS....WITH
LOWER CHANCES ON THE EASTERN PLAINS.

FOR THURSDAY NIGHT AND FRIDAY...AN UPPER LEVEL LOW WILL BE MOVING
VERY SLOWLY EAST ACROSS THE DESERT SOUTHWEST. AT THE SAME
TIME...LARGE SCALE Q-G LIFT IS EXPECTED TO INCREASE ACROSS THE
FORECAST AREA. THIS SHOULD SET UP ANOTHER WIDESPREAD RAIN EVENT
WITH POTENTIAL FOR MORE SIGNIFICANT PRECIPITATION ONCE AGAIN.
TEMPERATURES DO LOOK WARMER SO EXPECT SNOW LEVELS DURING THIS
PERIOD TO BE RATHER HIGH...WITH MOST OF THE ACCUMULATING SNOW
ABOVE TIMBERLINE. HAVE INCREASED POPS FOR THIS WETTER
PERIOD...WHILE KEEPING TEMPERATURES COOL WITH MOSTLY CLOUDY SKIES
AND SHOWERS/STORMS AROUND.

THIS NEXT UPPER TROUGH IS DIFFICULT TO TIME SO EFFECTS MAY VERY
WELL LINGER INTO FRIDAY NIGHT AND SATURDAY. MOST MODELS AGREE
THAT THE LOW DOES KICK A BIT MORE TO OUR NORTH THAN THIS CURRENT
STORM...SO MORE WIDESPREAD PRECIPITATION SHOULD BE SHIFTING NORTH
AND EAST OF THE FORECAST AREA. HOWEVER...THERE WILL BE SUFFICIENT
MOISTURE AND INSTABILITY UNDER THE UPPER LOW SO WILL CONTINUE A
CHANCE OF SHOWERS AND A FEW STORMS.

BY SUNDAY AND MONDAY PRECIPITATION CHANCES SHOULD DECREASE A BIT
IN BETWEEN WEATHER SYSTEMS...BUT THERE IS STILL PLENTY OF
RESIDUAL MOISTURE AROUND. THIS WILL KEEP TEMPERATURES SEVERAL
DEGREES BELOW NORMAL AND A FEW SHOWERS IN THE FORECAST.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z TUESDAY LATE AFTERNOON)
ISSUED AT 310 PM MDT MON MAY 18 2015

STRATUS DECK HAS GRADUALLY LIFTED THIS AFTERNOON WITH MVFR
CEILINGS. STILL VERY STABLE SO ONLY ISOLATED LIGHT RAIN SHOWERS
NEAR HIGHER TERRAIN. EXPECT SHOWERS TO INCREASE OVER TERMINALS
DURING THE EVENING HOURS AS LARGE SCALE ASCENT MOVES ACROSS THE
AREA. HAVE DOWNPLAYED THUNDER POTENTIAL BUT COULD BE A FEW
EMBEDDED THUNDERSTORMS THIS EVENING AND AGAIN LATER TNT AND EARLY
TUESDAY. SLOW IMPROVING CONDITIONS BY TUESDAY AFTERNOON. GUSTY
SOUTHEAST WINDS WILL DEVELOP TNT WITH A BIT OF CYCLONE SETTING UP
N-NW WINDS AT BJC AND POSSIBLY APA.

&&

.HYDROLOGY...
ISSUED AT 310 PM MDT MON MAY 18 2015

RAIN WILL BECOME WIDESPREAD OVER THE PLAINS TONIGHT AND CONTINUE
THROUGH TUESDAY. LATEST QPF FROM MODELS SHOWING ANYWHERE FROM .50
TO 1.5 INCHES OF RAIN ON THE PLAINS AND UP TO 2 INCHES POSSIBLE OVER
THE FRONT RANGE FOOTHILLS. LOWEST AMOUNTS OVER THE PALMER DIVIDE
AND THROUGH DENVER AS SOUTHEAST FLOW NOT AS FAVORABLE. HIGHER
AMOUNTS LOOK TO BE OVER LARIMER COUNTY WITH THE MORE FAVORABLE
SOUTHEAST FLOW. STILL SOME CONCERNS ABOUT RIVER FLOODING...AS
RIVERS AND CREEK FLOWS ARE ALREADY HIGH FROM RAINFALL LAST WEEK.
SMALL STREAMS COULD SEE SOME HIGHER FLOWS AGAIN WITH SOME MINOR
FLOODING LATER TNT AND TUESDAY.  ALSO SOME CONCERNS ALONG THE
CACHE LA POUDRE ABOVE FORT COLLINS COULD ALSO RIVER LEVELS AROUND
OR SLIGHTLY ABOVE FLOOD STAGE AGAIN BY TUESDAY AFTERNOON IF UP TO
2+ INCHES OF RAIN FALLS FROM THIS STORM. OVERALL FLOOD THREAT DOES
NOT SEEM HIGH AND WIDESPREAD ENOUGH TO ISSUE A FLOOD WATCH AT THIS
TIME. RAINFALL INTENSITIES WILL DECREASE DURING TUESDAY
AFTERNOON/EVENING.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM MDT TUESDAY
FOR COZ033-034.

&&

$$

SHORT TERM...ENTREKIN
LONG TERM...BARJENBRUCH
AVIATION...ENTREKIN
HYDROLOGY...ENTREKIN



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