Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 041025
AFDBOU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
425 AM MDT MON MAY 4 2015

.SHORT TERM...(TODAY THROUGH TONIGHT )
ISSUED AT 425 AM MDT MON MAY 4 2015

AIRMASS CONTINUES TO MOISTEN AS MOISTURE IS ADVECTED NORTH AHEAD
OF AN UPPER LOW MOVING OVER CA AND AZ TODAY. HIGH SURFACE PRESSURE
OVER THE DAKOTAS WILL KEEP EASTERLY UPSLOPE FLOW INTO THE STATE
TODAY...THEREFORE BRINGING A CLOUDY COOL DAY WITH GOOD PROBABILITY
OF RAIN. THE DETAILS IN TIMING AND COVERAGE ARE QUITE
DIFFICULT...ESPECIALLY WITH HIGH RES AND MESOSCALE MODELS SHOWING
DRASTICALLY DIFFERENT SOLUTIONS RUN TO RUN.  SCATTERED SHOWERS
THIS MORNING...MAINLY AGAINST THE FOOTHILLS AND SPREADING OVER THE
METRO AREAS SHOULD DECREASE SLIGHTLY THROUGH MID MORNING BEFORE WE
START TO DESTABILIZE A BIT AND SEE AN INCREASE IN COVERAGE AND A
THUNDERSTORMS THIS AFTERNOON. CAPES ARE NOT VERY HIGH AND CURRENT
PW VALUE AROUND 0.7" IS EXPECTED TO INCREASE SLIGHTLY MORE THROUGH
THE DAY...REACHING NEAR RECORD VALUES. THIS WILL MAKE
THUNDERSTORMS MORE PRONE TO LOCALLY HEAVY RAIN. WITH COOLER AIR
OVER THE FAR NORTHEASTERN PLAINS...MORE STABILITY IS EXPECTED
HOWEVER CANNOT TOTALLY RULE OUT TSTORMS. HAVE KEPT THEM OUT OF
THIS AFTERNOON TIME FRAME BUT INCLUDED THEM TONIGHT WHEN COOLER
MIDLEVEL AIR MOVES IN. THE UPSLOPE FLOW IS EXPECTED TO INCREASE
THROUGH THE DAY AND EVENING AND BECOME MORE SOUTHEASTERLY. THIS IS
A FAVORED DIRECTION FOR SOUTH PARK AND THE SOUTHERN FRONT RANGES
AND MOSQUITO RANGE.

AN AREA OF INCREASED MOISTURE WILL MOVE UP FROM THE SOUTH TONIGHT
FOR A CONTINUED CHANCE OF RAIN...POSSIBLY HEAVY AT TIMES WITH
EMBEDDED THUNDERSTORMS....MAINLY EAST OF THE DIVIDE.  AGAIN...DETAILS
ARE HARD TO PINPOINT DOWN. EXPECT SCATTERED TO NUMEROUS SHOWERS
AND MINIMUM TEMPERATURES TO REMAIN MODERATED UNDER LOW CLOUDS.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 425 AM MDT MON MAY 4 2015

...WET AND UNSETTLED WEATHER PATTERN REMAINS IN PLACE THIS WEEK...

THE UPPER LEVEL TROUGH WILL GET KICKED NORTHEAST ACROSS THE
FORECAST AREA TUESDAY AND TUESDAY NIGHT. UNSEASONABLY HIGH
PRECIPITABLE WATER VALUES...A SLIGHTLY UNSTABLE AIRMASS...AND
SKINNY CAPE PROFILES WILL KEEP A THREAT OF LOCALLY HEAVY RAINFALL
IN THE FORECAST. PW VALUES ON TUESDAY WILL RANGE ANYWHERE FROM
0.80 NEAR THE FRONT RANGE TO AS MUCH AS 1 INCH ON THE EASTERN
PLAINS...AT OR NEAR RECORD VALUES FOR THIS TIME OF YEAR.

Q-G LIFT...ALBEIT WEAK...WILL INCREASE AS THE SHORT WAVE
APPROACHES. THIS ALONG WITH A NEUTRAL TO SLIGHTLY UNSTABLE AIRMASS
AND THETA-E/MOIST ADVECTION FROM THE SOUTH SHOULD COMBINE TO BRING
A ROUND OF WIDESPREAD SHOWERS AND A FEW THUNDERSTORMS STARTING
TUESDAY MORNING. WHILE MODELS AGREE WELL IN THE LARGE SCALE
FEATURES...ANY CONVECTIVE COMPLEXES COULD MAKE BIG DIFFERENCES ON
WHERE THE HEAVIER RAIN FALLS. GIVEN THE WIDESPREAD PRECIPITATION
AND LIMITED INSTABILITY WITH CAPES OF JUST A FEW HUNDRED
J/KG...DONT SEE MUCH THREAT OF ANY SEVERE WEATHER. HOWEVER...THERE
MAY BE A THREAT OF SHORT LIVED WEAK TORNADOES AS LOW LEVEL WIND
FIELD STRENGTHENS AND LCLS WILL BE QUITE LOW IN THE 2000-3000 FT
RANGE.

BY LATE TUESDAY NIGHT INTO WEDNESDAY...THE UPPER LEVEL TROUGH
WILL BE MOVING NORTHEAST INTO THE CENTRAL HIGH PLAINS TAKING THE
MAIN AREA OF PRECIPITATION WITH IT. HOWEVER...THERE IS ENOUGH
INSTABILITY LINGERING IN THE STILL RATHER MOIST AND SLIGHTLY
UNSTABLE ENVIRONMENT BEHIND THE TROUGH AXIS TO KEEP A DECENT
CHANCE OF SHOWERS AND A FEW THUNDERSTORMS IN THE FORECAST THROUGH
WEDNESDAY. IT SHOULD BE NOTED THE HIGHER MOUNTAINS COULD ACTUALLY
SEE HEALTHY SNOW ACCUMULATIONS IN THE BACK EDGE DEFORMATION ZONE
OF UPPER TROUGH. SNOW LEVELS EXPECTED TO LOWER A BIT TUESDAY NIGHT
WITH SOME WEAK COLD ADVECTION...SO SNOW LEVELS MAY DROP TO
9500-10000 FEET. OVERALL...THE MORE SIGNIFICANT SNOW TOTALS SHOULD
BE LIMITED TO THE HIGHER MOUNTAIN PEAKS ABOVE 11-12 THOUSAND FEET
WHERE SEVERAL INCHES TO OVER A FOOT OF SNOW WILL BE POSSIBLE
THROUGH THIS EVENT.

A DRIER PERIOD IS STILL EXPECTED LATE WEDNESDAY NIGHT INTO
THURSDAY...ALTHOUGH STILL CANT RULE OUT ISOLATED TO SCATTERED
SHOWER AND STORM DEVELOPMENT AS MOISTURE DOES NOT SCOUR OUT
COMPLETELY.

FOR FRIDAY INTO NEXT WEEKEND...THE STRONGER UPPER LEVEL CLOSED
LOW DROPPING INTO THE DESERT SOUTHWEST AND ANOTHER FRONT BACKING
ACROSS THE PLAINS WILL KEEP THE CHANCE OF SHOWERS AND STORMS IN
THE FORECAST. IT NOW APPEARS THE THREAT OF SEVERE WEATHER WOULD BE
MUCH LOWER AS LONG AS THE COLD FRONT DROPS AND HOLDS FAR ENOUGH
SOUTH KEEPING US IN THE COOLER AIRMASS. A POST FRONTAL UPSLOPE
FLOW WOULD BRING HIGHER PRECIP CHANCES...SO POPS AT OR ABOVE
CLIMATOLOGY WOULD BE WARRANTED. COULD SEE MORE SNOW ACCUMULATION
OVER THE HIGHER MOUNTAINS AGAIN...THIS STORM SYSTEM SEEMS A
LITTLE COLDER THAN TUESDAYS SO SNOW LEVELS MAY REACH VALLEY FLOORS
WHENEVER UPPER TROUGH FINALLY MOVES ACROSS THE STATE.

&&

.AVIATION...(FOR THE TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 425 AM MDT MON MAY 4 2015

SCATTERED SHOWERS ARE EXPECTED TO CONTINUE PUSHING NORTH AND
DECREASING THROUGH MID MORNING. CEILINGS ARE EXPECTED TO CONTINUE
LOWERING HOWEVER WITH UPSLOPE FLOW...GENERALLY STAYING AROUND 2000
FEET. CEILINGS WILL THEN SLOWLY RISE THROUGH THE REST OF THE
MORNING AND INTO THE AFTERNOON...BUT REMAIN UNDER 5000 FEET. WILL
DESTABILIZE SLIGHTLY THIS AFTERNOON FOR A CHANCE FOR THUNDERSTORMS
MAINLY AFTER 20Z. AN INCREASE IN MOISTURE AND UPSLOPE FLOW THIS
EVENING WILL THEN INCREASE SHOWER COVERAGE AND LIKELY DROP
CEILINGS TO 1000 FT OR LESS THROUGH THE NIGHT. WINDS WILL BE OUT
OF THE EAST TO NORTHEAST WITH SPEEDS LESS THAN 15 KNOTS.

&&

.HYDROLOGY...
ISSUED AT 425 AM MDT MON MAY 4 2015

INCREASING PRECIPITABLE WATER VALUES TO NEAR RECORD
VALUES...UPSLOPE FLOW THROUGH THE DAY AND WIDESPREAD LIGHT UPWARD
MOTION WILL HELP PRODUCE WIDESPREAD SHOWERS TODAY WITH SOME
EMBEDDED THUNDERSTORMS. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE
TODAY WITH ALL THESE INGREDIENTS...ESPECIALLY TONIGHT WHEN UPSLOPE
FLOW INCREASES AND AN AREA OF ENHANCED MOISTURE MOVES UP FROM THE
SOUTH. RAINFALL RATES OF HALF AN INCH OR MORE IN 30 MINUTES ARE
POSSIBLE...ESPECIALLY WITH SLOW MOVING STORMS.

WIDESPREAD SHOWERS AND A FEW THUNDERSTORMS WILL OCCUR TUESDAY
WITH ADDITIONAL RAINFALL AMOUNTS EXPECTED TO AVERAGE AROUND ONE
HALF INCH. HOWEVER...WITH THE HIGH THETA-E AND PRECIPITABLE WATER
VALUES IN PLACE...SOME LOCATIONS COULD EASILY SEE RAINFALL AMOUNTS
IN EXCESS OF 1 INCH DURING THE DAY. AT THIS TIME...THIS FAVORS
POINTS JUST EAST OF THE FRONT RANGE I-25 CORRIDOR WITH THE DEEP
SOUTHERLY FLOW. JUST A BIT MORE TURNING THOUGH AND A STRONGER
EASTERLY COMPONENT INTO THE FRONT RANGE COULD BRING HEAVIER
PRECIPITATION THREAT TO THE I-25 CORRIDOR AND FOOTHILLS. SOME
POTENTIAL FOR FLOOD ISSUES IN BURN SCARS IF THAT SCENARIO UNFOLDS.
PRECIP RATES COULD STILL BE LIMITED BY WIDESPREAD NATURE OF
RAIN...AND ONLY ISOLATED TO SCATTERED THUNDERSTORMS PRODUCING THE
LOCALLY HEAVY RAINFALL.

THREAT OF HEAVIER RAINFALL WILL BE ENDING TUESDAY EVENING AS UPPER
TROUGH AND MAIN PRECIPITATION SHIELD PUSHES OFF TO THE NORTHEAST.

&&

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

$$

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


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