Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KBOU 181002
AFDBOU

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

.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 FAS 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 12Z TUESDAY MORNING)
ISSUED AT 402 AM MDT MON MAY 18 2015

NORTHEAST TO EAST WINDS WILL PREVAIL TODAY BEHIND A COLD FRONT THAT
PUSHED THROUGH LAST NIGHT. THIS WILL KEEP SKIES CLOUDY TODAY.
CEILINGS THIS MORNING...THROUGH 15Z...WILL BE 500 TO 1500 FEET AND
THEN SLOWLY RISE THROUGH THE DAY. EASTERLY WINDS WILL PREVAIL TODAY
AND TONIGHT. EASTERLY GUSTS TO 25 KNOTS WILL BE POSSIBLE AFTER 21Z
TODAY AND THROUGH TONIGHT. ISOLATED SHOWERS WILL PREVAIL THROUGH 00Z
TODAY AND THEN INCREASE WITH A PERSISTENT RAIN FORMING AFTER 06Z.
CEILINGS WILL FALL BELOW 2000 FEET TONIGHT. VISIBILITY MAY FALL
BELOW 5 MILES UNDER THE HEAVIER RAINFALL.

&&

.HYDROLOGY...
ISSUED AT 402 AM MDT MON MAY 18 2015

THE HEAVIEST RAINFALL TONIGHT IS EXPECTED TO BE SOUTH OF INTERSTATE
70 AND ALSO IN THE FOOTHILLS WHERE A HALF INCH TO ONE OF RAINFALL
WILL BE POSSIBLE BY SUNRISE TUESDAY MORNING.

ADDITIONAL RAINFALL AMOUNTS FROM 1 TO 1.5 INCHES WILL BE POSSIBLE
ON TUESDAY WITH THE MAIN FOCUS FM THE NORTHERN FOOTHILLS ACROSS
THE PLAINS. A FEW PLACES COULD SEE LOCALLY UP TO 2 INCHES. RIVER
LEVELS REMAIN HIGH DUE TO GROUND WATER FROM THE RAINS OVER THE
LAST TWO WEEKS. TEMPERATURES WILL BE COOL ENOUGH THAT SNOWMELT
WILL NOT BE A FACTOR...BUT WARM ENOUGH THAT THE MUCH OF THE
FOOTHILLS TERRAIN WILL RECEIVE SIGNIFICANT RAIN TO FLOW INTO THE
FRONT RANGE TRIBUTARIES TO THE SOUTH PLATTE. INTERESTS ALONG
NORTHERN COLORADO RIVERS... PARTICULARLY THE SOUTH PLATTE AND
OTHER LOCATIONS THAT HAVE FLOODED RECENTLY...SHOULD BE AWARE OF
THE POSSIBILITY OF RENEWED FLOODING AS EARLY AS TUESDAY IN THE
HEADWATERS AND DOWNSTREAM ON THE SOUTH PLATTE INTO NEXT WEEKEND.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
FOR COZ033-034.

&&

$$

SHORT TERM...MEIER
LONG TERM...RPK
AVIATION...MEIER
HYDROLOGY...MEIER/RPK


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.