Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 192122
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
322 PM MDT TUE MAY 19 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 321 PM MDT TUE MAY 19 2015

UPPER TROUGH OVER THE STATE WILL BEGIN LIFTING NORTHEAST TONIGHT
WITH A SHORTWAVE UPPER RIDGE TO PUSH OVERHEAD WEDNESDAY. HOWEVER
HIGH SURFACE PRESSURE WILL REMAIN OVER THE NORTHERN PLAINS TO KEEP
MOIST EASTERLY FLOW OVER NORTHEASTERN COLORADO. STRATIFORM RAIN
AND SNOW HAS TRANSITIONED TO SHOWERS WITH SOME THUNDERSTORMS
MOVING OVER THE MOUNTAINS. GROUND IS QUITE SATURATED SO EVEN
THOUGH EXPECTED RAIN AMOUNTS LATE THIS AFTERNOON INTO TONIGHT OVER
THE PLAINS AND LOWER FOOTHILLS IS ONLY AROUND A QUARTER INCH AT
BEST...THE GROUND IS NOT ABLE TO SOAK IN MUCH MORE. THE CURRENT
FLOOD ADVISORIES ARE EXPECTED TO EXPIRE THIS AFTERNOON HOWEVER ANY
AREA OF SLIGHTLY ENHANCED RAIN WILL HAVE TO BE WATCHED. COOLER AIR
HAS FILTERED OVER THE NORTHEAST PLAINS TO ALLOW SOME SNOW TO MIX
IN. EXPECT THIS TO CONTINUE OVERNIGHT...BUT LITTLE TO NO
ACCUMULATION IS EXPECTED. LOOKING AT FORECAST SOUNDINGS OVER THE
PLAINS...MID AND UPPER LEVELS BEGIN DRYING OUT OVERNIGHT...SO WILL
LIKELY BEGIN TO SEE MORE FOG AND DRIZZLE ACROSS THE PLAINS
TONIGHT. ALSO...QG VERTICAL VELOCITIES TURN WEAK DOWNWARD.
HOWEVER...WITH THE RIGHT ENTRANCE REGION OF THE JET MOVING
OVERHEAD...COULD SEE A FEW SCATTERED SHOWERS CONTINUE OVERNIGHT.
SNOW LEVELS ARE AROUND 8500 FT...BUT BESIDES THE SHOWERS AND
THUNDERSTORMS...SNOW WILL BE DIMINISHING. ADDITIONAL SNOW AMOUNTS
WILL LIKELY REMAIN BELOW 3 INCHES...EXCEPT FOR LOCALIZED AREAS
UNDER HEAVIER SHOWERS. TEMPERATURES REMAINED COOLER TODAY...SO
HAVE LOWERED MINIMUM TEMPERATURES TONIGHT BY A DEGREE OR TWO.

AS STATED ABOVE...THE SURFACE HIGH WILL CONTINUE TO PUSH IN A MORE
STABLE AND COOLER AIRMASS OVER THE PLAINS TOMORROW. WITH CONTINUED
CLOUD COVER EXPECTED...LOWERED MAX TEMPERATURES TOMORROW. SOME
INSTABILITY TO OCCUR OVER THE HIGH MOUNTAINS...HAVE INTRODUCED A
SLIGHT CHANCE OF SHOWERS OVER THE MOUNTAINS IN THE AFTERNOON. MAY
SEE SOME OF THESE SHOWERS PUSH OVER THE ADJACENT METRO AREAS AND
PALMER DIVIDE IN THE LATER AFTERNOON. OVERALL...LIGHT RAIN UP TO A
TENTH OF AN INCH EXPECTED FROM THESE SHOWERS...BUT GROUND RESPONSE
COULD BE QUICK.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 321 PM MDT TUE MAY 19 2015

SCATTERED SHOWERS AND A FEW THUNDERSTORMS ARE EXPECTED TO PUSH
SLOWLY EAST ONTO THE PLAINS THROUGH THE EVENING HOURS...ALTHOUGH
THERE SHOULD BE A GRADUAL WEAKENING AS THEY MOVE INTO THE MORE
STABLE AIRMASS ON THE EASTERN PLAINS.

MAIN ATTENTION WILL TURN TOWARD NEXT STORM SYSTEM DROPPING
SOUTHWARD ALONG THE CALIFORNIA COAST. THIS WILL BRING INCREASING
MOISTURE...AND AN EMBEDDED SHORT WAVE MOVING AHEAD OF THIS
FEATURE IS EXPECTED TO REACH COLORADO THURSDAY NIGHT. AHEAD OF
THIS...AIRMASS WILL DESTABILIZE ACROSS THE MOUNTAINS AND MAY EVEN
SEE ENOUGH DAYTIME HEATING ON THURSDAY TO HELP SURFACE BASED
CONVECTION DEVELOP ON THE NEARBY PLAINS. MAIN SHOT OF MORE
SIGNIFICANT AND WIDESPREAD PRECIPITATION IS EXPECTED TO ARRIVE
THURSDAY NIGHT AND FRIDAY AS THE LEAD SHORT WAVE PUSHES ACROSS
THE STATE. THERE IS ONCE AGAIN PLENTY OF LOW/MID LEVEL MOISTURE
AND HIGH PRECIPITABLE WATER VALUES TO BRING A THREAT OF LOCALLY
HEAVY RAINFALL. THIS SYSTEM IS WARMER AS WELL...SO COULD SEE RAIN
ON TOP OF SNOWPACK AS SNOW LEVELS MAY HOVER CLOSER TO 11 THOUSAND
FEET.

BY FRIDAY NIGHT AND SATURDAY...DEPENDING ON EVENTUAL TRACK OF
SYSTEM COULD SEE MORE NUMEROUS SHOWERS AND A FEW STORMS CONTINUE
ESPECIALLY IF UPPER LEVEL TROUGH HANGS A BIT FARTHER SOUTH AND
WEST WHICH IS ENTIRELY POSSIBLE LIKE THE ECMWF. HOWEVER...IF THE
GFS IS CORRECT WITH A FARTHER NORTH AND MORE OPEN WAVE THEN LOWER
COVERAGE OF SHOWERS AND STORMS. EVEN THEN...SHOULD STILL SEE A
DECENT CHANCE AS AIRMASS WILL REMAIN RATHER MOIST AND UNSTABLE
UNDER GENERAL TROUGHINESS. THE SAME CAN BE SAID THROUGH SUNDAY.

THERE SHOULD BE SOME GRADUAL MODERATION IN TEMPERATURES AND THE
EXTREMELY WET WEATHER PATTERN AS WE HEAD INTO MONDAY OR TUESDAY OF
NEXT WEEK AS THE FLOW TURNS MORE WESTERLY. HOWEVER...WILL HAVE TO
KEEP A CHANCE OF SHOWERS AND STORMS IN THE FORECAST EACH DAY WITH
LINGERING MOISTURE AND POTENTIAL FOR EMBEDDED BUT WEAKER DISTURBANCES.

&&

.AVIATION...(FOR THE TAFS THROUGH 00Z WEDNESDAY LATE AFTERNOON)
ISSUED AT 321 PM MDT TUE MAY 19 2015

LOW CLOUDS TO PREVAIL THROUGH TONIGHT. CEILINGS AROUND 1500-3000
FEET WILL LOWER OVERNIGHT...LIKELY BELOW 1000 FEET BY 12Z
WEDNESDAY...WITH AREAS OF DRIZZLE AND FOG. RAIN SHOWER COVERAGE WILL
CONTINUE TO DECREASE. A WEAK DENVER CYCLONE SEEMS TO BE FORMING
OVER SOUTHWEST DENVER COUNTY...WILL CONTINUE TO KEEP THE
NORTHERLY WINDS FOR BJC AND NORTHEAST WINDS FOR DEN AND APA LATER THIS
AFTERNOON. EASTERLY WINDS ARE EXPECTED AGAIN OVERNIGHT AND INTO
WEDNESDAY. CEILINGS WILL LIKELY STAY MVFR OR LOWER.

&&

.HYDROLOGY...
ISSUED AT 321 PM MDT TUE MAY 19 2015

SATURATED SOILS CONTINUE TO ALLOW EASY PONDING OF WATER OR MINOR
FLOODING OF LOW LYING AREAS ACROSS NORTHEAST COLORADO. RAINFALL
AMOUNTS WILL BE DECREASING...EXPECTING ABOUT A QUARTER OF AN INCH
MORE ACROSS FAR NORTHEAST COLORADO THROUGH TONIGHT....WITH ABOUT
TENTH OF AN INCH FURTHER SOUTH AND WEST TOWARD THE METRO AREA AND
PALMER DIVIDE. GOOD CONTINUOUS UPSLOPE FLOW INTO THE NORTHERN
FOOTHILLS IS ALLOWING FOR THE SMALL STREAM FLOOD ADVISORY THROUGH
6PM THIS EVENING. RAINFALL RATES WILL CONTINUE TO BE LESS THAN A
QUARTER INCH PER HOUR SO THE THREAT FOR FLASH FLOODING IS LOW.

RECENT RAINFALL DRAINING INTO THE LARGER RIVERS HAS PROMPTED THE
FLOOD WARNING STARTING TONIGHT FOR THE CACHE LA POUDRE NEAR
GREELEY AND THE SOUTH PLATTE FROM ADAMS COUNTY DOWNSTREAM THROUGH
WELD AND MORGAN TO NORTHWEST WASHINGTON COUNTIES AS THE RIVERS
RISE OVER THE NEXT FEW DAYS. EXPECT ELEVATED WATERS ALONG ALL
OTHER RIVERS ACROSS NORTHEAST COLORADO. THE ELEVATED CACHE LA
POUDRE NEAR FORT COLLINS IS EXPECTED TO REMAIN IN ITS BANKS.

NEXT RISK OF SIGNIFICANT AND WIDESPREAD PRECIPITATION IS EXPECTED
TO ARRIVE THURSDAY NIGHT AND FRIDAY. PRECIPITABLE WATER VALUES
WILL ONCE AGAIN BE HIGH WITH PLENTY OF GULF MOISTURE AVAILABLE TO
TAP INTO. THIS SYSTEM IS WARMER AS WELL...SO COULD SEE RAIN ON TOP
OF SNOWPACK AS SNOW LEVELS HOVER CLOSER TO 11 THOUSAND FEET.
RAINFALL POTENTIAL AT THIS TIME LOOKS TO BE ONE HALF TO ONE INCH
AMOUNTS FOR MOST LOCALES...WITH LOCALLY HEAVIER AMOUNTS FROM
THUNDERSTORMS. AS EVIDENCED BY THIS LAST STORM...GROUND IS
BECOMING SATURATED THROUGH A DEEP LAYER SO EFFICIENT RUNOFF MAY
LEAD TO MORE OR ENHANCED FLOODING ISSUES.

&&

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

&&

$$

SHORT TERM...KRIEDERMAN
LONG TERM...BARJENBRUCH
AVIATION...KRIEDERMAN
HYDROLOGY...KRIEDERMAN



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