Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 181705
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1105 AM MDT MON MAY 18 2015

.UPDATE...
ISSUED AT 1036 AM MDT MON MAY 18 2015

EARLY MORNING SHOWERS ARE DIMINISHING ACROSS NORTHEAST COLORADO AT
THIS TIME. THERE IS SOME GENERATION OF SHOWERS NOW OVER MOUNTAINS
AS MORNING HEATING WILL QUICKLY GIVE WAY TO SHOWERS/FEW
THUNDERSTORMS THIS AFTERNOON. MAIN CONCERN IS IMPACTS OF NEXT
APPROACHING STORM SYSTEM OVER CALIFORNIA. GENERALLY FORECASTS IN
GOOD SHAPE WITH BULK OF PRECIP DEVELOPING THIS EVENING WITH
HEAVIEST PRECIP LATE EVENING THROUGH TUESDAY MORNING. HAVE ALREADY
UPGRADED THE WINTER STORM WATCH TO A WARNING FOR THE MOUNTAINS
ABOVE 10000 FEET. INCREASED POPS OVERNIGHT AND TUESDAY WITH
DECREASING SHOWERS FROM SOUTHWEST TO NORTHEAST BY TUESDAY
AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 402 AM MDT MON MAY 18 2015

COLD FRONT PUSHED THROUGH OVERNIGHT AND IS PRODUCING A MOIST
NORTHEAST UPSLOPE FLOW OVER NORTHEAST COLORADO. LOW CLOUDS HAVE
FORMED ALREADY BEHIND THE FRONT. THERE IS ENOUGH LIFT BEHIND IT TO
TRIGGER ISOLATED SHOWERS OVER SOUTHERN PARTS OF THE AREA AND ALONG
THE FOOTHILLS. WILL BUMP UP POPS FOR THIS MORNING. EXPECT IT REMAIN
MOSTLY CLOUDY TODAY DUE TO THE MOIST UPSLOPE FLOW. THIS WILL KEEP
HIGHS IN THE 50S. AIRMASS OVER THE HIGHER TERRAIN WILL BECOME
UNSTABLE THIS AFTERNOON WITH CAPES UP TO 500 J/KG. OVER NORTHEAST
COLORADO...IT WILL BE STABLE BECAUSE OF THE COOL LOW LEVELS.
SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER THE HIGHER
TERRAIN THIS AFTERNOON WHERE IT BECOMES UNSTABLE.

LARGE UPPER LEVEL LOW OFF THE PACIFIC COAST WILL MOVE INLAND TODAY
AND THEN INTO THE GREAT BASIN TONIGHT. AS IT MOVES INTO THE GREAT
BASIN...THE FLOW ALOFT OVER EASTERN COLORADO WILL BECOME DIFFLUENT.
AT THE SURFACE...LOW PRESSURE WILL DEEPEN OVER THE GREAT BASIN AND
HIGH PRESSURE WILL STRENGTHEN OVER THE NORTHERN PLAINS. THIS WILL
CAUSE SOUTHEAST WINDS TO INCREASE ALONG THE FRONT RANGE AND EASTERN
PLAINS TONIGHT. IN ADDITION TO THIS...A STRONG SHORT WAVE ROTATING
AROUND THE UPPER LEVEL LOW WILL BE CENTERED OVER THE FOUR CORNERS BY
12Z TUESDAY.

EXPECTED THE SCATTERED SHOWERS AND STORMS TO MOVE OFF THE HIGHER
TERRAIN THIS EVENING. PRECIPITATION WILL TRANSITION TO A STRATIFORM
EVENT DUE TO THE LIFT PROVIDED BY THE UPSLOPE FLOW AND INCREASINGLY
DIFFLUENT FLOW ALOFT. ONE AREA THAT COULD RECEIVE HEAVY
PRECIPITATION TONIGHT MAY BE LARIMER COUNTY DUE TO THE STRONG
SOUTHEAST UPSLOPE FLOW. PRECIPITATION TOTALS BY 12Z TUESDAY WILL BE
AROUND HALF INCH. EXPECT A FEW AREAS TO SEE AROUND AN INCH...SUCH AS
THE FOOTHILLS OF LARIMER COUNTY. SNOW WILL FALL OVER THE MOUNTAINS
TONIGHT WITH LOCALLY UP TO 6 INCHES IN THE FAVORED AREA. SOME
UNCERTAIN HOW MUCH SNOW WILL FALL OVER PARTS OF ZONE 34 SO WILL
CONTINUE WITH THE WINTER STORM WATCH.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 402 AM MDT MON MAY 18 2015

AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE AREA ON TUE AND THEN EXIT
THE RGN BY TUE NIGHT.  QG FIELDS SHOW FAVORABLE ASCENT THRU THE AFTN
HOURS IN MOST AREAS WHICH WILL GRADUALLY WEAKEN BY TUE EVENING.  IN
THE LOWER LEVELS THE FLOW OVER NERN CO WILL BE MOSTLY SELY WHICH MAY
ALLOW FOR A DENVER CYCLONE TO FORM OVER THE PALMER DIVIDE.  IF THIS
HAPPENS THEN COULD SEE A MORE ELY COMPONENT DVLP NORTH OF DENVER TO
THE WY BORDER WHICH WOULD ENHANCE UPSLOPE FLOW ACROSS BOULDER AND
LARIMER COUNTIES.  OVERALL SHOULD SEE WIDESPREAD RAIN ACROSS LOWER
ELEVATIONS WITH SNOW LEVELS GENERALLY ABOVE 9000 FEET.  AT THIS TIME
HIGHEST THREAT FOR HEAVY SNOW APPEARS TO BE IN ZN 33 AND NRN AREAS
OF ZN 34.  RAIN AMOUNTS STILL COULD AVERAGE FROM 1 TO 1.5 INCHES
ACROSS THE PLAINS INTO THE NRN FOOTHILLS WITH LOCALLY UP TO 2 INCHES
IN SOME PLACES.  HIGHS WILL STRUGGLE TO GET ABVE 50 ACROSS MOST OF
NERN CO.

BY TUE NIGHT THE UPPER LEVEL SYSTEM WILL MOVE AWAY FM THE AREA WITH
PCPN GRADUALLY ENDING FM SW TO NE AS MID LVL DESCENT DVLPS.  ON WED
A FLAT UPPER LEVEL RIDGE WILL DVLP OVER THE AREA AS COOL SFC HIGH
PRES REMAINS OVER ERN CO.  THE AIRMASS ACROSS THE PLAINS WILL BE
STABLE WITH THE BEST INSTABILITY ACROSS THE HIGHER TERRAIN SO BEST
CHC OF SHOWERS AND A FEW TSTMS WILL BE ACROSS THE MTNS WHICH MAY
MOVE ACROSS THE FOOTHILLS AND PORTIONS OF THE URBAN CORRIDOR BY
MID TO LATE AFTN. HIGHS ON WED WILL ONLY BE IN THE LOWER TO MID
50S OVER NERN CO.

ON THU ANOTHER UPPER LEVEL TROUGH WILL MOVE INTO CALIFORNIA WITH
SWLY FLOW DEVELOPING OVER THE AREA.  AT THE SFC HIGH PRES WILL
CONTINUE TO AFFECT NERN CO WITH SELY LOW LVL FLOW.  OVERALL BELIEVE
ECMWF HAS A BETTER HANDLE ON HIGH TEMPS OVER NERN CO SO WILL KEEP
READINGS MAINLY IN THE UPPER 50S TO LOWER 60S.  AS FAR AS PCPN
CHANCES THE AIRMASS ACROSS THE PLAINS WILL REMAIN RATHER STABLE WITH
THE BEST INSTABILITY REMAINING OVER THE HIGHER TERRAIN.  THUS WILL
KEEP CHC POPS IN THE MTNS AND FOOTHILLS WITH ONLY A SLIGHT CHC OVER
THE PLAINS.

FOR THU NIGHT INTO FRI AN UPPER LEVEL LOW WILL BE OVER SRN
CALIFORNIA/WRN ARIZONA WITH INCREASING SWLY FLOW ALOFT.  BOTH THE
ECMWF AND GFS SHOW A DISTURBANCE MOVING INTO THE RGN WITH A DECENT
SHOT OF MID LVL ASCENT.  MEANWHILE SELY LOW LVL FLOW WILL CONTINUE
EAST OF THE MTNS WHICH WILL ALLOW FOR DEEPER LOW LVL MOISTURE TO
ADVECT INTO NERN CO.  OVERALL IT LOOKS LIKE THERE COULD BE ANOTHER
GOOD CHC OF MORE PCPN THU NIGHT INTO FRI.  AS FOR HIGHS FOR NOW WILL
KEEP READINGS IN THE LOWER TO MID 60S OVER NERN CO HOWEVER ABUNDANT
CLOUD COVER AND PCPN COULD KEEP READINGS IN THE 50S.

BY FRI NIGHT INTO SAT THE MAIN UPPER LEVEL TROUGH WILL MOVE INTO THE
AREA WITH SOME MORE MID LVL ASCENT.  WITH ABUNDANT MOISTURE AND
DECENT INSTABILITY IN PLACE WILL LIKELY SEE ANOTHER CHC OF
SHOWERS/TSTMS ON SAT WITH SOME SNOW IN THE MTNS.  HIGHS WILL
CONTINUE BLO NORMAL AS READINGS STAY IN THE LOWER TO MID 60S.  ON
SUN THE UPPER LEVEL TROUGH WILL MOVE SLOWLY EAST OF THE AREA HOWEVER
THERE WILL STILL BE ENOUGH MOISTURE AND INSTABILITY AROUND FOR AT
LEAST A SLIGHT CHC OF SHOWERS AND TSTMS.

&&

.AVIATION...(FOR THE TAFS THROUGH 18Z TUESDAY MORNING)
ISSUED AT 1036 AM MDT MON MAY 18 2015

STRATUS DECK WILL COVER TERMINALS THROUGH THE DAY BUT THERE WILL
BE A GRADUAL LIFT OF THE DECK THROUGH AFTERNOON. AIRMASS IS
INITIALLY STABLE ON THE PLAINS UNTIL ALMOST EVENING. COULD BE
SOME EMBEDDED THUNDERSTORMS BUT GENERALLY WIDESPREAD RAIN
DEVELOPING BY LATER THIS EVENING THROUGH TUESDAY MORNING. WINDS
WILL SHIFT SOUTHEAST THIS AFTERNOON AND CONTINUE THROUGH TONIGHT
WITH POSSIBLE GUSTS TO 25KT.


&&

.HYDROLOGY...
ISSUED AT 1036 AM 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. 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. ALSO SOME CONCERNS ALONG THE CACHE
LA POUDRE ABOVE FORT COLLINS COULD ALSO RIVER LEVELS 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.

&&

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

&&

$$

UPDATE...ENTREKIN
SHORT TERM...MEIER
LONG TERM...RPK
AVIATION...ENTREKIN
HYDROLOGY...ENTREKIN


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