Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 201139
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
639 AM CDT SUN JUL 20 2014

.SYNOPSIS...
ISSUED AT 634 AM CDT SUN JUL 20 2014

COLD FRONT FROM CENTRAL ND INTO CO WILL MOVE VERY SLOWLY
EWD...ENTERING IA TUESDAY AND PASSING SOUTHEAST OF THE AREA WED.
COOL HIGH PRESSURE WILL BUILD IN BEHIND THE COLD FRONT WED AND
THU.

&&

.SHORT TERM /TODAY/...
ISSUED AT 343 AM CDT SUN JUL 20 2014

SOUTH FLOW OF WILL DRAW MOISTURE INTO THE STATE WITH TEMPS TODAY
RUNNING A FEW DEGREES WARMER THAN HIGHS SAT. DEW POINTS WILL RISE
INTO THE MID 60S TO LOT 70S ACROSS THE CWA BY THIS AFTERNOON.
AREA OF MID LEVEL CLOUDS OVER THE NORTHEAST HALF OF THE STATE WILL
GRADUALLY PULL AWAY. EXPECT PLENTY OF SUNSHINE TODAY WITH WINDS A
LITTLE STRONGER THAN ON SATURDAY WITH SOME GUSTS TO AROUND 30 MPH
OVER THE NORTHWEST.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 343 AM CDT SUN JUL 20 2014

FORECAST REMAINED FOCUSED ON HEAT AND PRECIPITATION CHANCES
MONDAY AND TUESDAY AND THEN WITH COOLER TEMPERATURES THROUGH THE
REST OF THE WEEK. LEANED TOWARD A DRIER FORECAST PER NAM/ECMWF
MONDAY AND TUESDAY AS GFS SEEMS TOO AGGRESSIVE WITH BREAKING OUT
THUNDERSTORMS ON TUESDAY WITH COLD FRONT MOVING THROUGH THE STATE.

TONIGHT THROUGH WEDNESDAY...WAA CONTINUES TONIGHT INTO MONDAY WITH
DEEP MIXING DEVELOPING THROUGHOUT THE DAY MONDAY. 850MB TEMPS WARM
TO +24 OR SLIGHTLY HIGHER BY 21Z MONDAY BUT MIXING TO AROUND 900MB
MORE LIKELY. INCREASING SURFACE DEW POINTS TONIGHT INTO MONDAY WILL
AID IN THE SWELTERING HEAT INDEX READINGS BY MONDAY. NO MAJOR
CHANGES WITH ONGOING TEMPERATURE FORECAST FOR MONDAY AND HEAT INDEX
VALUES REMAIN JUST BELOW HEADLINE CRITERIA FOR MONDAY.

TUESDAY STILL ON TRACK TO BEING THE HOTTEST DAY OF THE SEASON
THUS FAR FOR MUCH OF THE FORECAST AREA. RAISED OVERNIGHT LOWS UP A
COUPLE DEGREES MONDAY NIGHT WITH THE WAA AND THETA-E ADVECTION
INTO THE STATE DURING THIS TIME. DEW POINTS RISE INTO THE MIDDLE
TO UPPER 70S...PLUS THE CORN MAY ADD A DEGREE OR TWO ONTO THE
SURFACE DEW POINTS. REGARDLESS...HEAT INDEX VALUES OVER THE 105
BY THE AFTERNOON ARE LIKELY. TIMING OF FRONT MOVING THROUGH THE
STATE WILL BE CRUCIAL AND THINK IT WILL MOVE ACROSS THE SOUTHERN
TWO-THIRDS OF THE FORECAST AREA LATE ENOUGH IN THE DAY TO NOT
HINDER THE MAX TEMPERATURES. CERTAINLY HEADLINE MATERIAL TUESDAY
AND ONE WILL BE CONSIDERED CLOSER TO THIS TIME PERIOD.

TREMENDOUS INSTABILITY ON TUESDAY BUT WITH LIMITED SHEAR AND A
VERY STRONG CAP AT 700MB (+16C)...AND LEANED TOWARD LESSER POPS
DURING THE DAY WITH THE STRONG CAP IN PLACE. STILL MAY SEE A FEW
STORMS BRIEFLY BREAK THROUGH THE CAP BUT WITH THE WEAK DEEP LAYER
SHEAR...ANY STORMS THAT DEVELOP WILL BE DIFFICULT TO SUSTAIN
THEMSELVES. MUCH COOLER BY WEDNESDAY WITH CAA AND REGION IN
NORTHWEST FLOW ALOFT AND SURFACE HIGH BUILDING INTO THE STATE.

THURSDAY THROUGH SATURDAY...HIGH PRESSURE GRADUALLY MOVES EAST AND
NEXT SYSTEM LOOKS TO MOVE THROUGH FRIDAY INTO SATURDAY...DEPENDING
OF THE EXTENDED MODEL. BETTER POPS ARE FRIDAY NIGHT PER
ECMWF...BUT EVEN THE GFS HINTING ON SHORTWAVE MOVING ACROSS LATER
IN THE PERIOD.

&&

.AVIATION...20/12Z
ISSUED AT 634 AM CDT SUN JUL 20 2014

SLY FLOW OF MOIST AIR WILL CONTINUE THROUGH THE TAF PERIOD. VFR
CONDITIONS EXPECTED WITH ONLY MID AND HIGH LEVEL CLOUDS. THE ONLY
CONCERN IS THE POSSIBILITY OF SOME MVFR FOG AND STRATUS FORMING
TOWARD SUNRISE MONDAY. PROBABILITY OF THAT IS LOW AT THIS TIME
AND DID NOT MENTION IN THE TAF`S BUT IT WILL NEED TO BE MONITORED.

OUTLOOK...VFR CONDITIONS WILL HOLD INTO MONDAY NIGHT. AS COLD
FRONT APPROACHES...THUNDERSTORMS ARE EXPECTED TO FORM ALONG THE
FRONT. THE PERIOD OF THUNDERSTORMS IS NOT LIKELY TO BE MORE THAN A
FEW HOURS AT ANY TAF SITE. VFR CONDITIONS BY WED THROUGH THU AS
HIGH PRESSURE BUILDS BACK INTO THE AREA.

&&

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

$$

SYNOPSIS...MS JUL 14
SHORT TERM...MS JUL 14
LONG TERM...PODRAZIK
AVIATION...MS JUL 14


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