Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 060859
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
359 AM CDT FRI MAY 6 2016

.SHORT TERM.../TODAY/
ISSUED AT 359 AM CDT FRI MAY 6 2016

UPPER RIDGE ACROSS THE CENTRAL UNITED STATES WILL BE MAIN PLAYER
TODAY PROVIDING QUIET WEATHER ACROSS IOWA AND SURROUNDING AREAS.
THERMAL RIDGING ACROSS THE PLAINS WILL SHIFT EASTWARD TODAY WITH
TEMPERATURES WELL ABOVE NORMAL THIS AFTERNOON HELPED BY AMPLE
SUNSHINE...DEEP MIXING AND DECENT SOUTHWEST WINDS.  HAVE KEPT
TEMPERATURES WELL INTO THE 80S AND MAY NOT BE WARM ENOUGH GIVEN
THE SETUP AND THE FACT THAT READINGS REACHED THE MID 90S IN
PORTIONS OF THE DAKOTAS YESTERDAY. OTHER CONCERN WOULD BE WITH
FIRE WEATHER. GIVEN THE DECENT MIXING...DEWPOINTS WILL LIKELY BE
LOWER THAN PREVIOUS FORECAST AND ANTICIPATE RELATIVE HUMIDITY
VALUES TO DROP WELL INTO THE 20S ALONG WITH BREEZY SOUTHWEST WINDS
BY AFTERNOON. HOWEVER...MOST OF THE FUELS ARE NOW QUITE GREEN
WHICH WILL LIMIT THE ABILITY OF FIRES TO SPREAD AS QUICKLY AND
WILL GO WITH AN SPS TO HIGHLIGHT THE GREATER FIRE POTENTIAL.

.LONG TERM.../TONIGHT THROUGH THURSDAY/
ISSUED AT 359 AM CDT FRI MAY 6 2016

ACTIVE WEATHER PATTERN DEVELOPS OVER THE WEEKEND AND LOOKS TO
CONTINUE THROUGHOUT MUCH OF NEXT WEEK. HENCE...MAJORITY OF FOCUS
WAS ON PRECIPITATION CHANCES OVER THE WEEKEND AND SEVERE WEATHER
POTENTIAL MONDAY.

TONIGHT INTO SUNDAY...MODELS REMAIN IN AGREEMENT WITH TIMING OF
COLD FRONT TO MOVE ACROSS THE STATE FROM NORTH TO SOUTH THROUGH
THE DAY SATURDAY. THE BETTER FRONTOGENETICAL FORCING AND MID-LEVEL
RH VALUES WILL BE BETWEEN 12-18Z SATURDAY AND HAVE HIGHEST POPS
GOING DURING THIS TIME WRT THIS SYSTEM. SURFACE HIGH BUILDS INTO
THE STATE SATURDAY AFTERNOON ACROSS NORTHERN IOWA AND WARDS OFF
ANY ADDITIONAL RAIN/STORM CHANCES AFTER 18Z. COULD EVEN GO DRIER
FURTHER SOUTH....EVEN TO THE INTERSTATE 80 CORRIDOR BY 21Z
SATURDAY AT THE LATEST. THE FRONT STALLS FROM EASTERN NEBRASKA TO
SOUTHEAST IOWA SATURDAY NIGHT INTO SUNDAY WITH A WEAK AREA OF
VORTICITY ADVECTING NORTHEAST AHEAD OF THE MAIN UPPER LOW EJECTING
OUT OF THE CENTRAL ROCKIES ON SUNDAY. STORM CHANCES RETURN NORTH
BY SUNDAY EVENING...OR AFTER 00Z MONDAY. HOWEVER...LOOKS AS IF
THE HIGH IS STUBBORN ENOUGH TO SLOW DOWN THE VORT MAX PROGRESSION
TO 03Z-06Z MONDAY. TEMPERATURES WILL BE TRICKY BOTH SATURDAY AND
SUNDAY DUE TO THE MANY ELEMENTS AT PLAY. WEAK CAA...CLOUD COVER
AND RAIN CHANCES ON SATURDAY AND THEN WITH THE FRONT MOVING BACK
NORTHWARD THROUGH THE DAY COMBINED WITH THE CLOUD COVER AND RAIN
CHANCES AGAIN. LEANED TOWARD THE WARMER GUIDANCE AS HAVE LOW
CONFIDENCE WITH ANY WIDESPREAD PRECIPITATION UNTIL MONDAY AND
LIKELY TO HAVE SOME EXTENDED BREAKS IN THE CLOUD DECK EACH DAY.

SUNDAY NIGHT INTO TUESDAY...THE AFOREMENTIONED DEEPLY STACKED LOW
PRESSURE SYSTEM CONTINUES TO MOVES OUT OF THE CENTRAL ROCKIES.
THIS RESULTS IN PLACING THE FORECAST AREA WITHIN SOUTHWEST FLOW
AND ALLOWS FOR SOME DECENT MOISTURE TO RETURN TO THE REGION.
SEVERAL VORT MAX FEATURES EMBEDDED IN THE 500MB FLOW WILL AFFECT
THE STATE LATE SUNDAY NIGHT INTO TUESDAY BEFORE THE UPPER LOW
FINALLY WEAKENS AND KICKS EASTWARD. THE FIRST SHORTWAVE WILL
AFFECT THE STATE BETWEEN 03Z TO MAYBE 15Z MONDAY BEFORE MOVING
NORTH INTO MINNESOTA AND PROVIDING A BRIEF BREAK MONDAY AFTERNOON.
THIS LOOKS TO ALLOW SOME INSTABILITY TO BUILD BACK INTO CENTRAL
AND SOUTHERN IOWA MONDAY AFTERNOON. GFS IS A BIT MORE POTENT WITH
THE NEXT SHORTWAVE TO PUNCH INTO THE STATE MONDAY
AFTERNOON/EVENING. THE DEEP LAYER SHEAR IS CONDUCIVE FOR LONGER
LASTING UPDRAFTS...BUT LOW LEVEL SHEAR IS NOT TOO IMPRESSIVE.
0-1KM HELICITY RANGES FROM 100-200 M2S2 DEPENDING THE MODEL AND
LITTLE TO NO CAP IN PLACE. HOWEVER...STORMS LOOK TO BE MAINLY
ELEVATED AS LCL HEIGHTS AROUND 1500-2000FT. CERTAINLY SEVERE
WEATHER POTENTIAL OVER THE SOUTHERN TWO-THIRDS OF THE CWA EXIST
MONDAY AFTERNOON/EVENING...BUT LOW CONFIDENCE IN TORNADIC ACTIVITYATTM.

BY TUESDAY...THE SURFACE LOW LOOKS TO BE LOCATED IN EASTERN
IOWA/NORTHERN ILLINOIS AND DRIER AIR ADVECTS INTO THE SOUTHWEST IN
THE AFTERNOON AND LEANED TOWARD LOWER POPS IN THIS LOCATION.

WEDNESDAY AND THURSDAY...ANOTHER UPPER LEVEL LOW IS LIKELY TO
AFFECT THE FORECAST DURING THIS TIME FRAME BUT MODELS REMAIN IN
DISAGREEMENT WRT TO TIMING AND LOCATION. THUS HAVE LOWER
CONFIDENCE IN ANY SEVERE WEATHER POTENTIAL.

&&

.AVIATION.../FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT/
ISSUED AT 1134 PM CDT THU MAY 5 2016

RELATIVELY LIGHT WINDS AND MOSTLY CLEAR SKIES ARE FORECAST
THROUGH THE PERIOD WITH VFR CONDITIONS EXPECTED.


&&

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

&&

$$

SHORT TERM...COGIL
LONG TERM...PODRAZIK
AVIATION...LEE



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