Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 202119
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
419 PM CDT WED MAY 20 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 419 PM CDT WED MAY 20 2015

THE MAIN PRECIPITATION SHIELD HAS PASS EAST OF THE MISSISSIPPI
THIS AFTERNOON. A VAST STRATUS FIELD REMAINS IN PLACE WITH AN AREA
OF DEEPER LOW LEVEL MOISTURE STILL LINGERING. WEAK FORCING AND
CONVERGENCE IS ONGOING WITH IN THIS LOW LEVEL MOIST LAYER WITH
LIGHT SHOWERS AND/OR DRIZZLE STILL OCCURRING OVER CENTRAL IOWA.
THIS PRECIPITATION WILL DIMINISH THROUGH THE REMAINDER OF THE
AFTERNOON AND IS EXPECTED TO BE DONE BY THIS EVENING. DRIER LOW
LEVEL AIR WILL ARRIVE OVERNIGHT WITH CLEARING EXPECTED ALONG WITH LIGHT
WESTERLY WINDS. SOME POTENTIAL FOR FOG OVERNIGHT THOUGH AT THIS
TIME EXPECT THE LIGHT WESTERLY WINDS AND INFLUX OF DRIER AIR WILL
DIMINISH POTENTIAL.

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
ISSUED AT 419 PM CDT WED MAY 20 2015

A MUCH MORE PLEASANT COUPLE DAYS UPCOMING FOR THURSDAY AND FRIDAY
WITH SURFACE HIGH PRESSURE THE PRIMARY INFLUENCE ON THE WEATHER
ACROSS IOWA. HIGHS THURSDAY WILL BE IN THE 60S AND 70S WITH BREEZY
WEST TO NORTHWEST WINDS OF 15 TO 25 MPH EXPECTED WITH GOOD MIXING
TO AROUND 775 MB. CUMULUS DEVELOPMENT DURING THE AFTERNOON
CERTAINLY IS POSSIBLE. SOME MODEST INSTABILITY OF 100-200 J/KG OVER
NORTHEAST IOWA BY THE AFTERNOON AS A WEAK FRONTAL MOVES THROUGH
THOUGH WARMER TEMPERATURES ABOVE THIS CAPPING WILL BUT A LID ON
VERTICAL DISPLACEMENT WITH ANY ACTIVITY LIKELY EAST OF IOWA. MUCH
LIGHTER WINDS ON FRIDAY WITH THE HIGH PRESSURE RIDGE MOVING ACROSS
THE STATE. THE INITIAL SHORT WAVE ENERGY WILL LIFT UP THROUGH THE
INCREASING SOUTHWEST FLOW DURING THE DAY FRIDAY WITH THE ENERGY
SPLITTING AND SHEARING OUR AS IT ARRIVES WITH THE FORCING AND
MOISTURE FALLING APART AS IT ARRIVES. A GOOD AMOUNT OF LOW LEVEL DRY
AIR WILL BE IN PLACE AS THIS ENERGY ARRIVES OVER THE SOUTHWEST.
POSSIBLE SOME LIGHT SHOWERS OR SPRINKLES DEVELOP BY THE AFTERNOON
BUT THE DRY AIR SHOULD END UP HAVE A BIG IMPACT. POSSIBLE THE
HIGHER LEVEL CLOUDS ARRIVE AND LIMIT HIGH TEMPERATURES. HAVE THE
COOLEST TEMPERATURES OVER THE SOUTHWEST WITH THE MORE LIKELIHOOD
OF CLOUDS TO OCCUR.

THE POTENTIAL FOR PRECIPITATION THROUGH THE HOLIDAY WEEKEND STILL
THE MAIN FORECAST CHALLENGE. THE UPPER LEVEL LOW PRESSURE MOVING
INTO THE DESERT SOUTHWEST TOWARD THE END OF THE WEEK THEN LIFTING
SLOWLY NORTHEAST THOUGH THE WEEKEND IS STILL ON TARGET. TRACKING
THE NUMEROUS IMPULSES LIFTING AHEAD OF THE SYSTEM THROUGH THE
INCREASING SOUTHWEST FLOW AND THE DRY AIR FROM THE EAST WILL BE
BIG FACTORS. THE AFOREMENTIONED DRIER AIR SHOULD CONTINUE TO BE A
BIG IMPACT INTO SATURDAY WITH MOST LOCATIONS REMAINING DRY THROUGH
THE DAY. THE BETTER POTENTIAL FOR SHOWERS AND THUNDERSTORMS
ARRIVES SATURDAY NIGHT THEN AGAIN SUNDAY AND MONDAY WHEN BETTER
GULF MOISTURE ARRIVES. THE SEVERE WEATHER THREAT THROUGH THE
PERIOD IS GENERALLY LOW BUT CERTAINLY CAN NOT DISCOUNT A FEW
SEVERE STORMS BUT OVERALL SHEAR IS MODEST AT BEST AND SATURATING
PROFILES WILL NOT BE CONDUCIVE TO LARGE HAIL PRODUCTION. A BIGGER
POTENTIAL MAY BE FOR LOCALIZED HEAVY RAINFALL WITH PWATS RISING
ABOVE 1.50 INCHES OCCURS.

BEYOND THIS PERIOD AS THE UPPER LEVEL SYSTEM PASSES...A CHANGE TO
A MORE ZONAL FLOW AND WARMER WEATHER. THE PERIOD WILL REMAIN
ACTIVE WITH ON AND OFF CHANCES FOR THUNDERSTORMS FOR THE END OF
THE EXTENDED.

&&

.AVIATION...20/18Z
ISSUED AT 1250 PM CDT WED MAY 20 2015

MVFR CIGS WILL ERODE FROM THE NORTH AND EAST THIS AFTERNOON OVER
CENTRAL IOWA...CLEARING THE STATE AROUND OR SHORTLY AFTER SUNSET.
WINDS WILL BE FROM THE NORTHEAST AT 5 TO 10 KTS THROUGH THE
EVENING...SWITCHING TO THE NORTHWEST AT 10 TO 15 KTS THURSDAY
MORNING.


&&

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

$$

SHORT TERM...SKOW/DONAVON
LONG TERM...DONAVON
AVIATION...SKOW


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