Area Forecast Discussion
Issued by NWS Des Moines, IA

Home | 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 260455
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1154 PM CDT SAT JUL 25 2015

...UPDATED FOR 26/06Z AVIATION FORECAST DISCUSSION...

.SHORT TERM /TONIGHT/...
ISSUED AT 309 PM CDT SAT JUL 25 2015

MAIN CONCERN INTO THE NIGHT WILL CONTINUE TO BE CONVECTIVE TRENDS.
SEPARATE NRN AND SRN STREAM SHORT WAVES PRODUCED MCSS OVER SD AND
NE/KS EARLIER TODAY WITH RESULTANT CLUSTERS SUSTAINING THEMSELVES TO
VARIED DEGREES AS THEY CROSSED THE MO RIVER INTO IA. THE
THERMODYNAMIC ENVIRONMENT IS QUITE VARIED DOWNSTREAM IN TERMS OF
BOTH MLCAPE AND MLCIN WITH SIOUXLAND CLUSTER HAVING MORE FAVORABLE
CONDITIONS AND BETTER EFFECTIVE SHEAR AS WELL. CLUSTER HAS WEAKENED
RECENTLY HOWEVER SO IT MAY BE MAINTAINING ITS MORE
KINEMATIC/ELEVATED ORIGINS RATHER THAN TRYING TO BE ROOTED LOWER AND
BECOME MORE SURFACE BASED. THUS...FOR THE TIME BEING...NEITHER AREA
IS OF TOO MUCH CONCERN FOR INTENSIFICATION WITH DOWNSTREAM
CONVERGENCE LACKING. WOULD TAKE AWHILE TO REALIZE THE EXTREME
UNCAPPED INSTABILITY NEAR THE QUAD CITIES.

CONFIDENCE IS SLIGHTLY BETTER UPSTREAM HOWEVER. CONDITIONS SEEM
FAVORABLE FOR DEVELOPMENT ACROSS SD WITH 0-1KM MOISTURE
CONVERGENCE...BACK EDGE OF SYNOPTIC SCALE LIFT AND MLCAPE/MLCIN ALL
APPEARING TO BE PHASED AND READY TO TRIGGER DEVELOPMENT...WHICH HAS
INDEED RECENTLY OCCURRED NORTH. THUS CANNOT ARGUE WITH NAM AND
SEVERAL CONVECTION ALLOWING MODELS WHICH FIRE SD MCS AND DROP IT
INTO IA EARLY SUN MORNING PER FORWARD PROPAGATING MCS VECTORS.
CURRENT KS/NE/SD MOISTURE TRANSPORT DOES WEAKEN SOMEWHAT AS IT VEERS
INTO IA OVERNIGHT...BUT SHOULD STILL BE SUFFICIENT TO SUSTAIN MCS.
INSTABILITY AND SHEAR WILL NOT BE EXTREME INTO IA...BUT MAY STILL BE
SUFFICIENT FOR SEVERE POTENTIAL TO EXTENT BEYOND CURRENT SPC DAY 1
OUTLOOK FOR EARLY SUN MORNING.


.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 309 PM CDT SAT JUL 25 2015

BEGINNING OF EXTENDED WILL BE MARKED BY LARGE RIDGE BUILDING INTO
NORTHERN PLAINS. EXPECT ANY PRECIPITATION ONGOING SUNDAY MORNING
TO PUSH QUICKLY EAST. HOWEVER...MAY SEE ADDITIONAL THUNDERSTORM
CHANCES IN THE AFTERNOON WITH BAND OF FORCING PUSHING EAST. MODELS
ARE NOT IN GOOD AGREEMENT WITH AMOUNT OF INSTABILITY AND
SHEAR...WITH NAM SIGNIFICANTLY MORE AGGRESSIVE THAN GFS...THOUGH
BOTH ARE SUFFICIENT TO WARRANT THUNDERSTORM POTENTIAL AND CHANCES
FOR ISOLATED SEVERE IN THE AFTERNOON. HAVE KEPT FORECAST DRY FOR
LATE SUNDAY NIGHT...EXPECTING SYSTEM TO PUSH EAST.
HOWEVER...CHANCES FOR THUNDERSTORMS WILL CONTINUE THROUGH MONDAY
AND TUESDAY AS LARGE LOW PRESSURE SYSTEM DEVELOPS IN THE NORTHWEST
TO HELP PUSH RIDGE EAST. WAVE PUSHING THROUGH MONDAY MAY BRING
PRECIPITATION TO THE SOUTH LATE IN THE DAY...THOUGH BEST FORCING
IS PRIMARILY TO THE WEST OF IOWA. BEST CHANCES FOR PRECIPITATION
BEGIN MONDAY NIGHT AND BOUNDARY PUSHES INTO MISSOURI RIVER VALLEY
WITH SURFACE LOW LIFTING NORTHEAST. MONDAY NIGHT PRECIPITATION
CONTINUES TO BE CONFINED PRIMARILY TO THE NORTH...NORTH OF IOWA.
HOWEVER...HAVE INCLUDED PRECIPITATION CHANCES FURTHER SOUTH GIVEN
MODEL UNCERTAINTY AND AMOUNT OF FORCING. HOWEVER...STRONG CAP
NOTED IN SOUNDINGS...ESPECIALLY IN THE NORTH AND MAY BE TOO
AGGRESSIVE WITH POPS MONDAY AND TUESDAY. BEST CHANCES FOR
PRECIPITATION WILL COME TUESDAY NIGHT AS BOUNDARY PUSHES SOUTH
ACROSS CENTRAL IOWA.

RIDGE WILL BRING CONTINUED HOT AND HUMID TEMPERATURES THROUGH
TUESDAY...WITH TUESDAY EXPECTED TO BE HOTTEST HOTTEST DAY AS RIDGE
SLIDES EAST. MAY NEED HEAT ADVISORY AT TIMES THROUGH
TUESDAY...ESPECIALLY IN THE SOUTH. WILL HOLD OFF ATTM WITH SOME
UNCERTAINTIES IN TEMPERATURES TRENDS DUE TO PRECIPITATION CHANCES
INTERFERING WITH HEATING. BEHIND BOUNDARY TUESDAY THROUGH END OF
THE PERIOD WILL SEE COOLER CONDITIONS...AND GENERALLY DRY.
TEMPERATURES WILL BE GENERALLY NEAR NORMAL.

&&

.AVIATION...26/06Z
ISSUED AT 1154 PM CDT SAT JUL 25 2015

UNSETTLED WX EXPECTED DURING THE VALID PERIOD. TSRA COMPLEX IS
EXPECTED TO TRACK SOUTHEAST FROM SOUTH DAKOTA INTO NORTHWESTERN IOWA
OVERNIGHT...MOVING FARTHER SOUTHEAST INTO IOWA. KFOD...KMCW AND KDSM
TERMINALS LOOK TO BE MOST AFFECTED. OVERALL VFR FLIGHT RULES
EXPECTED...HOWEVER MVFR/IFR PSBL IN CONJUNCTION IN VICINITY OF TSRA.
ADDITIONAL SHRA/TSRA CHANCES ON SUNDAY ESPECIALLY ACROSS THE EASTERN
HALF OF IA...IMPACTING THE KALO/KOTM TERMINALS.

&&

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

&&

$$

SHORT TERM...SMALL
LONG TERM...AWB
AVIATION...ZOGG


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