Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 291751
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1251 PM CDT MON JUN 29 2015

.UPDATE...
ISSUED AT 1111 AM CDT MON JUN 29 2015

UPDATE TO TRIM POP ACROSS THE AREA THROUGH MID/LATE AFTERNOON AS
FORCING VERY LIMITED. CURRENTLY UNSTABLE...BUT OVERALL NO SFC
CONVERGENCE. SMOKE FROM SASKATCHEWAN FOREST FIRES CONTINUES TO
MOVE SOUTHEAST OVER THE AREA THIS AFTERNOON/TONIGHT. LITTLE IMPACT
TO AFTERNOON HIGHS EXPECTED...PERHAPS A DEGREE OR SO COOLER
NORTHEAST WHERE SMOKE IS THICKEST. SUNSET SHOULD BE QUITE
BRILLIANT RED THIS EVENING WHERE CLOUDS REMAIN THIN ENOUGH TO
VIEW. HAVE RAISED HIGHS ACROSS THE SOUTH...WHERE DSM ALREADY AT 80
AT 11 AM. /REV

&&

.SHORT TERM /TODAY/...
ISSUED AT 214 AM CDT MON JUN 29 2015

MAIN FORECAST CONCERN DURING THE SHORT TERM PERIOD IS
SHRA/TSRA...AND POSSIBLE SVR...CHANCES THIS AFTERNOON.

BEFORE THE SHRA/TSRA CHANCES THIS AFTERNOON...THOUGH...WILL BE FOG
CONSIDERATIONS EARLY THIS MORNING. COMBINATION OF LIGHT WINDS AND
AMPLE LOW-LEVEL AND GROUND MOISTURE HAS LED TO FOG FORMATION. IT IS
THICKEST ACROSS THE EAST CENTRAL AND SOUTHEASTERN CWA. PRESENTLY
DENSE FOG ADVISORY CRITERIA IS BEING MET ONLY IN ISOLATED
AREAS...BUT WILL HAVE TO MONITOR TRENDS FOR A POSSIBLE SHORT-FUSED
ADVISORY ISSUANCE IF CONDITIONS WORSEN.

FOCUS THEN SHIFTS TO AFTERNOON THUNDERSTORM AND SVR CHANCES. THE CWA
WILL BE UNDER THE INFLUENCE OF DEEP LAYER NORTHWESTERLY FLOW. A
SHORTWAVE WILL BE DROPPING DOWN THROUGH THE FLOW ACROSS MN/WI DURING
THIS TIME...BRINGING AN AREA OF MODEST MID- TO UPPER-LEVEL ASCENT IN
ADVANCE OF IT. AFTERNOON TEMPS WILL REACH THE LOWER THE MIDDLE
80S...WHICH WOULD MEET OR EXCEED CONVECTIVE TEMPS. DEWPOINTS WILL BE
IN THE LOWER TO MIDDLE 60S...RESULTING IN MLCAPES AS HIGH AS 1.5 TO
2.0 KJ/KG. MODELS ARE PROGGING 0-6KM EFFECTIVE SHEAR AS HIGH AS 20
TO 30 KT. DECENT LOW- AND MID-LEVEL LAPSE RATES WILL EXIST AS WELL.
MID-LEVEL MOISTURE WILL BE MORE PLENTIFUL ACROSS THE NORTHEASTERN
HALF OF THE CWA. THE AFOREMENTIONED FACTORS POINT TO ISOLD-SCT
SHRA/TSRA DEVELOPMENT ESPECIALLY ACROSS THE NORTHEASTERN CWA. HI-RES
MODELS ALSO DEPICT THIS POSSIBILITY. SHEAR AND LAPSE RATE PARAMETERS
SUGGEST POSSIBILITY OF DISCRETE CELLS WITH LARGE HAIL POTENTIAL.
GREATEST POTENTIAL OF SVR CRITERIA HAIL WILL BE ACROSS THE FAR N/NE
CWA...AS WELL AS POINTS TO THE N/NE IN MN/WI...WHERE PARAMETERS ARE
SLIGHTLY MORE FAVORABLE...PER SPC DY1 OUTLOOK. MEAN STORM MOTION OF
APPROX 310 DEG AT 30-35 KT...ALONG WITH FAVORABLE LOW-LEVEL LAPSE
RATES...SUGGEST ANY STORMS THAT DO DEVELOP MAY ALSO BE ABLE TO
PRODUCE ISOLD DAMAGING WIND GUSTS AS WELL.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 214 AM CDT MON JUN 29 2015

BEGINNING TO SOUND LIKE A BROKEN RECORD...BUT THE STORY FOR THE
FORECAST CONTINUES TO SEE LITTLE TO NO CHANGE OVER THE LAST FEW
ITERATIONS WITH NORTHWEST FLOW DOMINATING THROUGH THE END OF THE
WEEK. AS A RESULT...TEMPERATURES REMAIN ON TRACK TO BE SEASONABLY
COOL AND ON THE ACTIVE SIDE WITH MULTIPLE SHORTWAVES MOVING
THROUGH AND BRINGING SHOWER AND STORM CHANCES ON MULTIPLE DAYS THIS
WEEK.

THE FIRST PERIOD OF THE LONG TERM...MONDAY EVENING/OVERNIGHT...WILL
SEE THE REGION SKIRTED BY A WEAK LOW PRESSURE SYSTEM/TROUGH.
GOOD INSTABILITY AND FORCING ON THE WEAK SIDE WILL BE ENOUGH FOR
A FEW STORMS ACROSS THE NORTH AND EAST...BUT WITH LITTLE OTHER
SUPPORT COME THE EVENING/OVERNIGHT AND THE THREAT EXITING THE AREA...SEVERE
POTENTIAL IS LOW. A SHORT BREAK SHOULD BE HAD THROUGH TUESDAY
AFTERNOON BEFORE THE NEXT WAVE MOVES IN AND PRODUCES SHOWERS AND
STORMS ACROSS WESTERN...CENTRAL...AND SOUTHERN IOWA WITH A GOOD
VORTICITY AND THETA-E PUSH...LIKELY OVERCOMING NEAR- SURFACE DRY
AIR. THE DRY POCKET NEAR THE SURFACE COUPLED WITH OVERNIGHT
TIMING/LACK OF INSTABILITY SHOULD RESULT IN GENERIC THUNDER AT
BEST. GUIDANCE SUGGESTS THE WEEKS DEEPEST TROUGH THURSDAY NIGHT
INTO FRIDAY MAY PROVIDE A WIDESPREAD SHOT AT PRECIPITATION...BUT
MODELS CONTINUE TO DISAGREE IN TIMING AND MAGNITUDE OF
PRECIPITATION. CURRENTLY THE EURO IS THE FASTEST AND WETTEST
BRINGING IT IN THURSDAY AFTERNOON/EVENING AND CANADIAN AND GFS
BOTH SLOWER AND DRIER. THE WETTER/MORE AGGRESSIVE EURO DEPICTS
WEAK INSTABILITY AND SUPPORT FOR ORGANIZED STORMS...LENDING TO A
SHOWERS/GENERIC THUNDER THREAT MORE THAN ANYTHING SEVERE.

THURSDAY INTO FRIDAY ALSO SIGNALS THE BEGINNING OF THE END OF THE
NORTHWEST FLOW WITH MORE ZONAL FLOW GRADUALLY SETTING IN. THE
CANADIAN TRIES TO PUSH A SIZABLE TROUGH INTO THE REGION...BUT IS
THE OUTLIER WHILE THE EURO/GFS SOLUTIONS BUILDING IN THE TREND TO
ZONAL FLOW AND SOME RIDGING THROUGH THE HOLIDAY WEEKEND AND INTO
THE NEXT WEEK.

&&

.AVIATION...29/18Z
ISSUED AT 1250 PM CDT MON JUN 29 2015

MAIN CONCERNS WILL BE COVERAGE AND TIMING OF CONVECTION. THOUGH
UNSTABLE...LITTLE FORCING OR INITIATION MECHANISM CURRENTLY TO
FORCE THUNDER THIS AFTERNOON. CU FIELD MAY SEE A FEW STRONGER
UPDRAFTS AND -TSRA BETWEEN 20-23Z...BUT MAIN FORCING OF SYNOPTIC
BOUNDARY OVER MN WILL BE THE BETTER TRIGGER TODAY...WITH SCT
THUNDER MOVING SOUTH TOWARD IA/MN BORDER BETWEEN 22-00Z. SMOKE
FROM FIRES IN SASKATCHEWAN CONTINUES TO DRIFT SOUTH OVER IOWA. THOUGH
SFC OBSTRUCTIONS HAVE NOT BEEN OBSERVED...LAYER OF SMOKE MAY CAUSE
SOME RESTRICTION ALOFT OR ON APPROACH GIVEN THE COVERAGE AND
DEPTH. WINDS WILL REMAIN NEAR 10-12KT GUSTS 15 KTS THROUGH 00Z. AS
DIURNAL HEATING WANES...CONVECTION WILL END AND CONDITIONS REMAIN
QUIET THROUGH END OF PERIOD. /REV

&&

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

$$

UPDATE...REV
SHORT TERM...ZOGG
LONG TERM...CURTIS
AVIATION...REV


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