Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 212050
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
350 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 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...21/18Z
ISSUED AT 1242 PM CDT THU MAY 21 2015

WIDESPREAD VFR CONDITIONS ARE EXPECTED FOR THE DURATION OF THE
FORECAST WITH UNRESTRICTED VISIBILITIES AND CEILINGS. GUSTY WNW
WINDS ARE EXPECTED THIS AFTERNOON BECOMING LIGHT AND VARIABLE
OVERNIGHT.


&&

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

$$

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



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