Area Forecast Discussion
Issued by NWS Des Moines, IA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KDMX 180839
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
339 AM CDT SAT OCT 18 2014

.SYNOPSIS...
ISSUED AT 327 AM CDT SAT OCT 18 2014

HIGH PRESSURE FROM WESTERN ONTARIO INTO OKLAHOMA WILL MOVE EAST OF
IA TONIGHT AS A WEAK TROUGH MOVES THROUGH THE STATE ON SUNDAY
NIGHT. A STRONGER WEATHER SYSTEM WILL MOVE THROUGH THE UPPER
MIDWEST WEDNESDAY NIGHT AND THURSDAY.

&&

.SHORT TERM /TODAY/...
ISSUED AT 327 AM CDT SAT OCT 18 2014

TODAY WILL BE MARKED BY SIGNIFICANTLY COLDER AND WINDER CONDITIONS
COMPARED TO YESTERDAY AS A POTENT CLOSED 300 MB LOW DIVES SOUTHEAST
FROM CANADA TO SOUTHEAST MINNESOTA BY 00Z SAT. STRONG SURFACE TO 850
MB CAA IS ALREADY POURING INTO NORTH CENTRAL IOWA WITH 850 MB TEMPS
OVER DES MOINES PROGGED TO FALL FROM +8 C AT 06Z TODAY TO -3C BY
18Z. DIFFERENTIAL CAA IN THE BOUNDARY LAYER WILL QUICKLY STEEPEN
LAPSE RATES TO NEAR ADIABATIC OVER NORTH CENTRAL IOWA THIS MORNING.
COMBINED WITH A RAPIDLY TIGHTENING PRESSURE GRADIENT--12 MB ACROSS
THE STATE BY 15Z--SURFACE WINDS OF 25-30 KTS WITH GUSTS CLOSE TO 40
KTS WILE BE COMMON ACROSS THIS REGION TODAY. HAVE SHIFTED THE WIND
ADVISORY FORWARD IN TIME FROM 15Z TO 23Z AND EXPANDED IT TO INCLUDE
MORE COUNTIES IN WEST CENTRAL AND NORTH CENTRAL IOWA. WINDS MAY
ACTUALLY FALL BELOW ADVISORY CRITERIA EARLIER THAN THE CURRENT
EXPIRATION TIME AS THE BEST PRESSURE RISES AND CAA SHIFT OFF TO THE
EAST AFTER 18-21Z AND THE PRESSURE GRADIENT RELAXES.

A 500MB SHORTWAVE AND ATTENDANT VORT MAX VISIBLE ON WATER VAPOR
IMAGERY ENTERING NORTH CENTRAL NEBRASKA WILL SLIDE SOUTHWEST OF THE
CWA THIS MORNING. AN AREA OF LIGHT RAIN THAT HAS FORMED IN THE
KINEMATIC FORCING OUT AHEAD OF THIS WAVE IS EXPECTED TO TAKE A
SOUTHEASTERLY COURSE AS WELL. THIS IS WELL HANDLED BY THE HIGH RES
WRF ARW/NMM MODELS AND USED THIS GUIDANCE FOR THE MORNING FORECAST.
THIS RESULTED IN BACKING OFF ON THE PREVIOUS POPS AND THUS ONLY
HAVE THE FAR SOUTHWEST CWA UNDER A SLIGHT CHANCE OF RAIN BEFORE 18Z.

LAST BUT NOT LEAST...A LARGE STRATUS/STRATOCUMULUS SHIELD ON THE 11-
3.9 IMAGERY IS RACING SOUTHEAST WITH THE CAA AND ENTERING THE
NORTHWEST CWA. THESE CLOUDS EXTEND BACK TO EASTERN MONTANA AND SEE
NO REASON FOR THEM DISSIPATING TODAY. WITH NO MODEL SOLUTION
HANDLING THE CLOUDS...HAVE EDITED SKY GRIDS THE OLD FASHION WAY AND
HELD ONTO MOSTLY CLOUDY WORDING FOR THE CWA FOR MUCH OF THE
DAY...CLEARING SKIES FROM THE WEST LATE AS UPPER LEVEL SUBSIDENCE
WORKS ACROSS THE MISSOURI RIVER. LOWERED HIGHS SLIGHTLY FOR TODAY
BUT OVERALL DID NOT MAKE ANY MAJOR TEMP MODIFICATIONS.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 327 AM CDT SAT OCT 18 2014

AS THE HIGH MOVES OFF TO THE EAST AND WINDS SWING TO THE
SOUTH...WARMER AIR WILL MOVE RAPIDLY INTO THE STATE. TEMPS WILL
RISE ABOUT 10 DEGREES ON SUNDAY VS SATURDAY FOR HIGHS. MILD
WEATHER WILL CONTINUE INTO MONDAY...TOUGH SOME COOLING WILL FOLLOW
THE PASSAGE OF THE COLD FRONT...BUT IT WILL BE VERY MINOR.

THE NEXT WEATHER FEATURE FOR MID WEEK HAS STRONGER UPPER LEVEL
SUPPORT AND WILL BRING WITH IT A CHANCE FOR SHOWER ACROSS THE CWA.
MOISTURE WILL BE LIMITED AD DO NOT EXPECT MORE THAN SCATTERED
COVERAGE. ONCE AGAIN...THE COOLING WILL BE LIMITED BEHIND THE
SYSTEM. BUILDING HEIGHTS WILL CONTINUE OVER THE CENTRAL U.S.,
KEEPING THE ARCTIC AIR AT BAY. THUS...MILD PACIFIC AIR WILL RULE
THROUGH THE REST OF THE FORECAST PERIOD.


&&

.AVIATION...18/06Z
ISSUED AT 1137 PM CDT FRI OCT 17 2014

THE LARGE STRATOCUMULUS SHIELD HAS CONTINUED TO CREEP SOUTHWARD AS
EXPECTED...HOWEVER CIG HEIGHTS HAVE BEEN MORE VARIABLE THAN
ANTICIPATED RANGING ANYWHERE FROM FL017 TO FL048. SATELLITE
IMAGERY ALSO DEPICTS A LARGE HOLE MOVING FROM SOUTHERN MINNESOTA
INTO NORTHERN IOWA IN WHICH SKIES ARE VIRTUALLY CLEAR BEFORE
FILLING IN AGAIN FURTHER NORTH. ALL IN ALL STILL EXPECT BKN-OVC
MOST OF THE TIME THROUGH SAT MORNING BEFORE THE CLOUDS FINALLY
BEGIN TO CLEAR OUT...HOWEVER JUDGING FROM RECENT AND UPSTREAM
OBS...PERIODS OF MVFR WILL REMAIN POSSIBLE FOR AT LEAST THE NEXT
8 HOURS BUT DIFFICULTY OF PREDICTING EXACT TIMING AND LIMITED
OVERALL EXTENT DICTATE MOSTLY VFR CIGS ADVERTISED IN THE TAFS
ATTM.


&&

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

$$

SYNOPSIS...MS
SHORT TERM...FAB
LONG TERM...MS
AVIATION...LEE


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.