Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 212339
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
639 PM CDT THU MAY 21 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 349 PM CDT THU MAY 21 2015

THE QUIET WEATHER TODAY WILL PERSIST INTO TONIGHT WITH WEAK
SUBSIDENCE ACROSS THE STATE AS HIGH PRESSURE MOVES OVERHEAD.  SKIES
WILL REMAIN CLEAR WITH A DRY AIRMASS IN PLACE AND LIGHT WINDS
ALLOWING READINGS TO DROP NICELY OVERNIGHT.  HAVE LOWERED TEMPS
SLIGHTLY IN FAVORED LOCATIONS IN THE NORTHEAST AND NISHNA VALLEYS
WITH GOOD RADIATIONAL COOLING EXPECTED.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 349 PM CDT THU MAY 21 2015

HIGH PRESSURE WILL CONTINUE TO SHIFT EAST OF THE AREA ON FRIDAY
WITH RETURN SOUTHERLY FLOW INCREASING THROUGH THE DAY. MOISTURE
ADVECTION ALOFT AT 700 MB AND ABOVE WILL ARRIVE THROUGH THE
AFTERNOON WITH INCREASING CLOUDS. SHORT WAVE ENERGY WILL ARRIVE
DURING THE AFTERNOON AS WELL ALONG WITH GOOD KINEMATIC FORCING.
THE ELEVATED FORCING OVER WESTERN IOWA CONTINUES TO LOOK BETTER
AS THE PERIOD GETS CLOSER AND EXPECT SOME SHOWERS TO DEVELOP OVER
FAR WEST TO SOUTHWEST IOWA. THE PRIMARY QUESTION IS IF IT WILL
ARRIVE OVER THE FAR WESTERN FORECAST AREA DURING THE AFTERNOON.
HAVE KEPT MOSTLY DRY FOR THE MOMENT BUT BECOMING LESS CONFIDENT IN
A DRY SOLUTION AND LIKELY WILL NEED TO ADD POPS ACROSS THE WEST
FOR FRIDAY AFTERNOON AND EVENING. HAVE KEPT LOW POPS FOR SATURDAY
AND OVERALL THE DAY WILL BE MOSTLY DRY.

THE LOW LEVEL JET WILL SHIFT EAST SATURDAY NIGHT AND WILL BE
POINTING INTO THE STATE BY LATE SATURDAY NIGHT INTO SUNDAY.
PROFILES WILL BE SATURATING DURING THIS PERIOD WITH PWATS NEAR 1.6
INCHES OR GREATER BY 12Z SUNDAY MORNING AND PUSHING 1.75 BY LATER
IN THE DAY. THE SATURATED SOUNDINGS WILL LIMIT OVERALL INSTABILITY
AND THE SEVERE WEATHER THREAT. THE POTENTIAL FOR HEAVY RAINFALL
HOWEVER WILL BE THERE. WARM CLOUD DEPTHS OF 10-11 KFT ALONG WITH
HIGH PWATS WILL LEAD TO EFFICIENT RAIN PRODUCING STORMS. IN
ADDITION...STORM MOTIONS AND THE PERSISTENT MOISTURE ADVECTION AND
FORCING THROUGH THE DAY WILL LEAD TO NUMEROUS ROUNDS OF
THUNDERSTORMS WITH SOME AREAS RECEIVING AN ABUNDANCE OF RAIN.
EXPECT LOCALLY HEAVY RAINFALL TO OCCUR...WITH THE POTENTIAL FOR
IT TO BECOME MORE WIDESPREAD. WILL NEED TO MONITOR THIS POTENTIAL
WITH UPCOMING FORECASTS AND WILL ADD TO THE HWO. THE GENERAL
EVOLUTION OF THE SYSTEM BEYOND SUNDAY REMAINS UNCHANGED WITH THE
UPPER LOW TO THE WEST LIFTING NORTHEAST AND BECOMING AN OPEN WAVE
BY MONDAY WITH THE MAIN FRONTAL BOUNDARY STILL IN THE VICINITY.
WHILE THE PWATS BACK OFF TO NEAR 1.2 INCHES...A BETTER POTENTIAL
FOR SEVERE WEATHER WILL EXIST WITH HIGHER AND FATTER CAPES WHICH
WILL BE MORE CONDUCIVE TO PARTICLE ACCELERATIONS AND STRONGER
UPDRAFTS IN ADDITION TO BETTER LOW LEVEL AND DEEP LAYER SHEAR. TOO
EARLY TO DETERMINE EXACT SEVERE THREATS BUT COULD BE CONDUCIVE TO
A FEW SUPERCELLS.

THE REMAINDER OF THE FORECAST WILL FEATURE THE TRANSITION TO A
MORE ZONAL BUT STILL ACTIVE FLOW. THE EXTENDED IS LITTERED WITH
THUNDERSTORM CHANCES WHICH WILL SOUND MORE WET THAT WHAT WILL
OCCUR BUT THE POTENTIAL IS THERE FOR ANY GIVEN 12 HOUR PERIOD BUT
MOST PERIODS WILL BE MORE DRY THAN WET. TEMPERATURES WILL RETURN
TO MORE LATE MAY LIKE READINGS WITH HIGHS GENERALLY IN THE 70S AND
80S.

&&

.AVIATION...22/00Z
ISSUED AT 639 PM CDT THU MAY 21 2015

VFR CONDITIONS ARE ANTICIPATED THROUGH THE PERIOD. SCATTERED BAND
OF NW-SE AC WILL DISSIPATE OR PUSH AWAY FROM KDSM/KOTM DURING THE
EVENING LEADING TO CLEAR SKIES. WINDS WILL BE LIGHT AND
VARIABLE...THEN LIGHT SLY INTO PEAK HEATING FRI.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...COGIL
LONG TERM...DONAVON
AVIATION...SMALL


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