Area Forecast Discussion
Issued by NWS Des Moines, IA

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465
FXUS63 KDMX 292342
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
642 PM CDT FRI APR 29 2016

.SHORT TERM.../TONIGHT/
ISSUED AT 336 PM CDT FRI APR 29 2016

EASTERLY FLOW STRATUS/STRATOCU WILL PERSIST THROUGH TONIGHT WITH
CANADIAN HIGH PRESSURE TO THE NORTH AND A DEEPENING CYCLONE TO THE
SOUTH. LITTLE DIURNAL CHANGE IN TEMPERATURE IS LIKEWISE EXPECTED
TONIGHT WITH LOWS ONLY ABOUT 5 TO 10 DEGREES BELOW TODAY`S HIGHS.
H300 NEGATIVELY TILTED TROUGH OVER THE FOUR CORNERS REGION IN 18Z
WATER VAPOR IMAGERY WILL LIFT NORTHEASTWARD INTO THE WESTERN HIGH
PLAINS TONIGHT...PULLING THE AFOREMENTIONED 1002 MB SOUTHERN PLAINS
LOW INTO NORTHEAST KANSAS BY 12Z SATURDAY. LINE OF SHOWERS AND
THUNDERSTORMS CURRENTLY ACROSS KANSAS AND OKLAHOMA WILL PIVOT
NORTHEASTWARD TONIGHT AND REACH SOUTHWEST IOWA AROUND
03Z...ENCOMPASSING THE SOUTHERN TWO-THIRDS OF THE CWA BY THE END OF
THE PERIOD. BROAD 295-305K ISENTROPIC ASCENT/H500 HEIGHT FALLS AHEAD
OF THE SYSTEM AND DEEP MOISTURE TRANSPORT OFF THE GULF OF MEXICO
WILL CONTINUE TO SUPPORT THIS BROAD SWATH OF RAINFALL INTO IOWA.
MODERATE TO LOCALLY HEAVY RAINFALL WILL OCCUR OVER MANY OF THE SAME
REGIONS THAT SAW HIGH RAINFALL AMOUNTS EARLIER IN THE WEEK. THIS MAY
RESULT IN A RENEWED LOCALIZED FLOODING THREAT IN AREAS OF POOR
DRAINAGE. RIBBON OF H850 THETA-E ADVECTION BELOW 200-300 J/KG OF
MUCAPE MAY IGNITE ISOLATED THUNDERSTORMS AFTER 06Z SOUTH OF I-80.

.LONG TERM.../SATURDAY THROUGH FRIDAY/
ISSUED AT 336 PM CDT FRI APR 29 2016

PRIMARY FORECAST CONCERNS ARE PRECIPITATION TRENDS AND RAINFALL THIS
WEEKEND...THEN TEMPERATURES NEXT WEEK.

SATURDAY THRU SUNDAY...FORECAST CONFIDENCE: MEDIUM/HIGH

A SEASONABLY STRONG UPPER LEVEL CLOSED LOW WILL WOBBLE SLOWLY
EASTWARD ACROSS IOWA THIS WEEKEND. GOOD AGREEMENT AMONGST THE
SHORT RANGE MODELS/ENSEMBLES AND CAM SOLUTIONS LIFTING A
WIDESPREAD EAST/WEST BAND OF PRECIPITATION NWD ACROSS IOWA DURING
THE DAY ON SATURDAY. EXPECT THE HEAVIEST PRECIPITATION TO FALL
ACROSS THE SRN HALF OF THE STATE IN THE MORNING HOURS...AND IN THE
NORTH IN THE AFTERNOON. A MAJORITY OF THE MODELS CONTINUE TO
DEPICT 200-300 J/KG OF MUCAPE IN THE SOUTH...SO WILL KEEP AN
ISOLATED MENTION OF THUNDER IN THE FORECAST FOR NOW. AS MENTIONED
PREVIOUSLY...A DRY SLOT WILL PIVOT INTO SRN IOWA IN THE
AFTERNOON...WITH A LOSS OF DEEP SATURATION AND LIFT.
HOWEVER...WOULD NOT BE SURPRISED TO SEE PATCHY DRIZZLE IN THE
AFTERNOON DUE TO RESIDUAL SATURATION IN THE 1000-800MB LAYER...MAY
NEED TO ADD EXPLICIT MENTION OF THIS LATER. THE SFC BOUNDARY
SHOULD REMAIN SOUTH OF THE AREA IN THE AFTERNOON...SO AT THIS TIME
BELIEVE A MAJORITY OF THE AFTERNOON CONVECTION WILL REMAIN OVER
MISSOURI. ALTHOUGH THE UPPER LOW IS EXPECTED TO WEAKEN ON
SUNDAY...EXPECT A CONTINUATION OF COOL TEMPERATURES...CLOUDY SKIES
AND SCATTERED SHOWERS AS WEAK FORCING AND PERIODS OF DEEPER
SATURATION PERSIST. STORM TOTAL RAINFALL AMOUNTS THIS WEEKEND ARE
EXPECTED TO RANGE FROM 0.5 TO 1.5 INCHES...WHICH COULD LEAD TO
SOME MINOR FLOODING ISSUES IN MORE FLOOD PRONE AREAS.

MONDAY THROUGH FRIDAY...FORECAST CONFIDENCE: MEDIUM

AFTER THE UPPER LOW DEPARTS ON MONDAY...MAINLY DRY CONDITIONS ARE
FORECAST FOR MUCH OF THE EXTENDED. THE SYNOPTIC PATTERN WILL
FEATURE UPPER RIDGING OVER THE ROCKIES AND TROUGHING IN THE EAST.
THERE IS THE POSSIBILITY OF SEVERAL WEAK SHORTWAVES TO DROP SWD
ALONG THE EAST FLANK OF THE AMPLIFYING RIDGE ON MONDAY AND AGAIN
ON WEDNESDAY. OVERALL FORCING AND MOISTURE/SATURATION SHOULD BE
LIMITED...SO DECIDED TO KEEP THE FORECAST DRY FOR NOW.
TEMPERATURES SHOULD GRADUALLY MODERATE INTO THE 60S AND 70S NEXT
WEEK...ALTHOUGH WILL NEED TO KEEP AN EYE ON POTENTIAL FOR A COUPLE
SHOTS OF COOLER AIR IF THE ABOVE MENTIONED SYSTEMS MATERIALIZE.

&&

.AVIATION.../FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING/
ISSUED AT 642 PM CDT FRI APR 29 2016

MVFR CEILINGS EXPECTED OVERNIGHT WITH SOME VFR CEILINGS IN THE FAR
NORTH WHERE DRIER AIR WILL WORK IN FROM THE EAST.  HOWEVER...
CEILINGS WILL BEGIN FALLING OVERNIGHT AS SHOWERS BEGIN ADVANCING
NORTHWARD INTO THE STATE. SURFACE WINDS WILL INCREASE FROM THE
EAST TO NORTHEAST DURING THE PERIOD AND BE QUITE STRONG ON
SATURDAY. IFR CONDITIONS WILL BE WIDESPREAD ON SATURDAY WITH AREAS
OF RAIN AND DRIZZLE PRODUCING VERY LOW CEILINGS AND RESTRICTED
VISIBILITIES THROUGH THE END OF THE PERIOD.

&&

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

&&

$$

SHORT TERM...SKOW
LONG TERM...FOWLE
AVIATION...COGIL



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