Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 132335
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
635 PM CDT SUN JUL 13 2014

...UPDATED AVIATION DISCUSSION...

.SHORT TERM /TONIGHT/...
ISSUED AT 323 PM CDT SUN JUL 13 2014

WEAK WIND SHIFT CONTINUES TO MOVE ACROSS THE AREA THIS AFTERNOON AND
NEARLY TO THE METRO A THIS TIME. SCATTERED SHOWERS AND THUNDERSTORMS
HAVE DEVELOPED ALONG THE BOUNDARY. MAIN CONCERNS WILL BE A FEW WIND
GUSTS AND BRIEF DOWNPOURS AS THEY PASS TO THE SOUTHEAST. LINGERING
SHOWERS/ISO THUNDER THIS EVENING AS THE WIND SHIFT/COOL FRONT SOUTH
THROUGH THE REGION. THE BOUNDARY SHOULD LINGER OVER THE SOUTH WITH
SCATTERED SHOWERS INCREASING AGAIN BETWEEN 06Z AND 12Z AS COOLER AIR
ALOFT CATCHES UP WITH THE WARM LAYER NEARER THE SFC. BUFR SOUNDINGS
SHOW INSTABILITY INCREASING SLIGHTLY DURING THIS TIME AND H850
FRONTAL BOUNDARY SHOWS SOME INTENSIFICATION. GIVEN THE INCREASED
DYNAMICS AND INSTABILITY OVER THE FAR SOUTH...WILL KEEP POPS GOING
FOR THE LATTER HALF OF TONIGHTS FORECAST PERIOD OVER THE SOUTH. LOWS
TONIGHT WILL BEGIN THE SLIDE WITH LOWER 50S OVER THE FAR NORTH AND
LOWER 60S IN THE FAR SOUTH. WINDS WILL BECOME LIGHT NORTHWEST
FOLLOWING THE PASSAGE OF THE BOUNDARY THIS EVENING.

.LONG TERM /MONDAY THROUGH SUNDAY/...
ISSUED AT 323 PM CDT SUN JUL 13 2014

A REINFORCING COLD FRONT WILL BE MOVING ACROSS THE AREA ON MONDAY
MORNING...SWEEPING ANY OVERNIGHT STORMS OUT TO THE SOUTH BY NOON
AND USHERING IN SEVERAL DAYS OF MUCH COOLER AND MOSTLY DRY
WEATHER. ON MONDAY AFTERNOON AS A LARGE 500 MB GYRE MOVES OVER
WISCONSIN TOWARD THE GREAT LAKES IT WILL GENERATE A LARGE SHIELD
OF STRATOCUMULUS CLOUDS AND ISOLATED TO SCATTERED LIGHT
SHOWERS...BUT THESE SHOULD ONLY GRAZE OUR NORTHEASTERN COUNTIES
AND PRODUCE NEGLIGIBLE EFFECTS. THE BIGGER STORY WILL BE THE DROP
IN TEMPERATURES WHICH WILL BE PRONOUNCED FOR THIS TIME OF THE
YEAR...WITH LOWS MONDAY NIGHT/TUESDAY MORNING DIPPING INTO THE
UPPER 40S IN SOME AREAS...POSSIBLY APPROACHING DAILY RECORDS AT A
FEW STATIONS.

FROM TUESDAY THROUGH FRIDAY THERE WILL BE A CHANCE FOR A FEW SMALL
LIGHT SHOWERS EACH AFTERNOON...BUT THE PROBABILITY OF RAIN AT ANY
GIVEN SPOT IS SO LOW THAT IT IS NOT MENTIONED IN THE OUTGOING
FORECAST. TEMPERATURES WILL SLOWLY REBOUND AFTER TUESDAY...GAINING
A FEW DEGREES EACH DAY THROUGH THE REST OF THIS WEEK. THE LARGE
COOL SURFACE HIGH PRESSURE AREA DOMINATING THE REGION WILL FINALLY
MOVE AWAY BY THURSDAY...ALLOWING FOR A RETURN OF SOUTHEASTERLY AND
THEN SOUTHERLY WITH HIGHS RETURNING TO THE 80S IN MOST AREAS.

BY FRIDAY A DEEP LAYER RIDGE WILL BE BUILDING ACROSS THE
SOUTHWESTERN U.S. AND INTO THE HIGH PLAINS...WITH A 500 MB
SHORTWAVE TROUGH DIGGING INTO SOUTHERN CANADA AND THE NORTHERN
U.S. ROCKIES. THE GFS KEEPS THIS TROUGH TO OUR NORTH ACROSS CANADA
RESULTING IN CONTINUED DRY WEATHER FOR IOWA...WHILE THE ECMWF HAS
CONSISTENTLY BEEN RIDING THE TROUGH AROUND THE NORTHEASTERN
PERIPHERY OF THE DEEP RIDGE AND ACROSS IOWA AND THE MIDWEST ON
SATURDAY NIGHT AND SUNDAY RESULTING IN A CHANCE FOR THUNDERSTORMS.
GIVEN THE CONSISTENCY OF THE ECMWF SOLUTIONS AND ITS RECENT
PERFORMANCE HAVE MAINTAINED CHANCE POPS IN THE FORECAST IN THE
MIDDLE OF THIS WEEKEND...BUT CONFIDENCE IS PRETTY LOW AND ANY
IMPACTS WOULD PROBABLY BE MINIMAL GIVEN THE SYNOPTIC SETUP. AT ANY
RATE...IN WAKE OF THIS TROUGH AND ITS POSSIBLE INFLUENCE ON OUR
AREA...ALL LONG RANGE INDICATORS AGREE THAT THE SOUTHWESTERN U.S.
RIDGE WILL BUILD MORE POWERFULLY...RESULTING IN A LIKELIHOOD OF
DRY AND MUCH HOTTER WEATHER FOR ROUGHLY THE FIRST HALF OF NEXT
WEEK.

&&

.AVIATION...14/00Z
ISSUED AT 633 PM CDT SUN JUL 13 2014

VFR CONDITIONS WILL PREVAIL DURING THE TAF PERIOD WITH MAIN
CONCERN OF GUSTY WINDS DEVELOPING TOMORROW BEHIND SHARP COLD
FRONT. MAY SEE A STRAY SHOWER WITH THE COLD FRONT TOMORROW AND
HAVE VCSH MENTIONED AT OTM.

&&

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

&&

$$

SHORT TERM...REV
LONG TERM...LEE
AVIATION...PODRAZIK



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