Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 161115
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
615 AM CDT THU APR 16 2015

.SHORT TERM /TODAY/...
ISSUED AT 400 AM CDT THU APR 16 2015

CENTRAL IOWA WILL GENERALLY REMAIN BETWEEN TWO WEATHER SYSTEMS FOR
TODAY. LARGE UPPER LEVEL LOW PRESSURE SYSTEM IN FOUR CORNERS REGION
WILL BEGIN TO INFLUENCE ARE FOR END OF PERIOD. HOWEVER...DIMINISHING
INFLUENCE FROM HIGH PRESSURE ACROSS THE EAST WILL CONTINUE TO KEEP
CONDITIONS PRIMARILY DRY THROUGH THE DAY. HOWEVER...INCREASING
INSTABILITY ASSOCIATED WITH LOW PRESSURE SYSTEM WILL BEGINNING TO ENTER
THE AREA AFTER 18Z. ENOUGH INSTABILITY TO WARRANT THUNDER MENTION IN
THE WEST IN THE AFTERNOON...HOWEVER...WEAK CAP WILL BE IN PLACE
WHICH SHOULD BE ENOUGH TO LIMIT MOST DEVELOPMENT AND HAVE ONLY
ISOLATED THUNDER MENTION IN THE WEST. WITH INCREASING WAA AND GOOD
MIXING IN THE AFTERNOON HAVE WARMED TEMPERATURES A FEW DEGREES FOR
TODAY. HOWEVER...WITH CLOUDS IN PLACE THROUGH THE DAY...MAY BE TOO
WARM.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 400 AM CDT THU APR 16 2015

THE PRIMARY FORECAST CHALLENGE THROUGH SATURDAY WILL BE
PRECIPITATION TIMING AS THE UPPER LEVEL SYSTEM NEAR THE 4 CORNERS
REGION BEGINS TO LIFT SLOWLY NORTHEAST FRIDAY BEFORE GAINING MORE
MOMENTUM ON SATURDAY. COMPLICATING THE TIMING IS A PERSISTENT VERY
DRY HIGH PRESSURE SYSTEM THAT HAS BEEN STRETCHED ACROSS THE
NORTHERN PLAINS AND GREAT LAKES REGIONS THE PAST SEVERAL DAYS.
HAVE RELEGATED ANY PRECIPITATION CHANCES TO THE FAR SOUTHWEST
THROUGH FRIDAY. THE FIRST SEGMENT IMPULSE EMANATING FROM THE
UPPER LEVEL LOW WILL LIFT INTO CENTRAL IOWA FRIDAY NIGHT IN
CONJUNCTION WITH SIGNIFICANT MOISTURE TRANSPORT LIFTING INTO THE
REGION. THIS WILL BRING GOOD WAVE OF FORCING FRIDAY NIGHT FOLLOWED
BY ANOTHER PUSH OF STRONGER FORCING SATURDAY AFTERNOON AND
EVENING. PARCEL STATIC STABILITIES WILL BE QUITE LOW ALONG WITH
MODEST MUCAPES AND INCREASING MID LEVEL LAPSE RATES WILL RESULT IN
A FEW THUNDERSTORMS. EAST TO NORTHEAST WINDS MAY ERODE THE
PRECIPITATION AS IT TRIES TO PUSH INTO THE NORTHEAST AREAS
INCLUDING WATERLOO AND MASON CITY HOWEVER THE SFC FLOW IS LIGHT
FRIDAY NIGHT SO MAY SEE PRECIPITATION REACH THOSE REGIONS WITH THE
INITIAL WAVE THEN DIMINISH AS THE SFC FLOW INCREASES ON SATURDAY
BEFORE POPS INCREASE AGAIN LATER. HAVE INCREASE POPS THROUGH MUCH
OF THIS PERIOD. SATURATED PROFILES ACROSS CENTRAL IOWA LATE
SATURDAY INTO SATURDAY NIGHT WILL NOT BE OVERLY CONDUCIVE TO
SEVERE WEATHER BUT CERTAINLY COULD RESULT IN BRIEF PERIODS OF
HEAVY RAINFALL. THE SYSTEM WILL BEGIN LIFT NORTHEAST THROUGH THE
STATE SATURDAY NIGHT AS ANOTHER STRONG SYSTEM DIVES INTO THE
NORTHERN PLAINS. PRECIPITATION WILL LIKELY LINGER THROUGH SUNDAY
BEFORE DRIER AIR ARRIVES LATER IN THE DAY. A BOUNDARY THAT WILL
MOVE ACROSS IOWA ON SUNDAY WILL BRING GUSTY NORTHWEST WINDS LATE
IN THE DAY INTO SUNDAY NIGHT.

A TRANSITION TO CYCLONIC FLOW OVER IOWA WILL LEAD TO COOLER
CONDITIONS ACROSS THE STATE AS THE SECOND STRONG SYSTEM BECOMES A
CLOSED LOW AND TAKES AN EXTENDED STAY OVER THE WESTERN GREAT LAKES
REGION. ANOTHER SYSTEM MOVING INTO THE DESERT SOUTHWEST WILL HELP
ENSURE THE WARMER SOUTHERN STREAM REMAINS SOUTH OF THE STATE
THROUGH MUCH OF NEXT WEEK. HIGH TEMPERATURES MAY BE TOO HIGH
TUESDAY INTO WEDNESDAY WITH 850 MB TEMPERATURES FALLING BELOW
ZERO CELSIUS. THAT SAID...THE FLOW WILL BE CONDUCIVE TO DEEP
MIXING AND BREEZY CONDITIONS WHICH WILL KEEP READINGS WARMER THAN
WHAT WOULD OTHERWISE BE EXPECTED.

&&

.AVIATION...16/12Z
ISSUED AT 611 AM CDT THU APR 16 2015

CONDITIONS WILL REMAIN PRIMARILY VFR THROUGH PERIOD. LOW VFR
CEILINGS MAY DROP TO MVFR BRIEFLY AT WESTERN SITES KFOD/KDSM NEAR
12Z. WINDS WILL BE GENERALLY LIGHT AND FROM THE EAST BECOMING
SOUTHERLY. WINDS WILL BECOME VARIABLE AFTER 00Z. MAY SEE MVFR
CEILINGS NEAR 12Z...BUT HAVE NOT INCLUDED MENTION ATTM DUE TO
UNCERTAINTIES IN TIMING AND LOCATION.

&&

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

&&

$$

SHORT TERM...AWB
LONG TERM...DONAVON
AVIATION...AWB



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