Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 091121
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
621 AM CDT WED JUL 9 2014

.SHORT TERM /TODAY/...
ISSUED AT 310 AM CDT WED JUL 9 2014

ANOTHER QUIET AND RELATIVELY COOL DAY IS IN STORE AS A HIGH
PRESSURE RIDGE REMAINS DRAPED ACROSS THE REGION. SKIES WILL BE
MOSTLY SUNNY WITH A REPEAT OF YESTERDAYS SHALLOW CUMULUS
CLOUDS...AND AGAIN A SLIM CHANCE FOR A FEW TINY LIGHT SHOWERS IN
THE NORTH BUT WITH PROBABILITY AND IMPACT TOO LOW TO EVEN MENTION
IN THE FORECAST. HIGH TEMPERATURES ARE A BIT TRICKY TODAY GIVEN
SEVERAL COMPETING FACTORS. YESTERDAY SAW TEMPERATURES RISE FURTHER
THAN EXPECTED DESPITE DECENT COLD AIR ADVECTION WITH BRISK
NORTHWEST WINDS AND SCATTERED TO BROKEN CLOUDS ACROSS THE NORTH.
TODAY WINDS WILL BE CONSIDERABLY LIGHTER WITH FEWER
CLOUDS...SUPPORTING EVEN WARMER TEMPERATURES. HOWEVER...WITH THE
HIGH NOW FIRMLY OVERHEAD THE AIR MASS IS STARTING OUT A BIT
COOLER AS EVIDENCED BY EARLY MORNING TEMPERATURES ACROSS THE
REGION...AND THE ELEVATED SMOKE PLUME EMANATING FROM WILD FIRES IN
NORTHERN CANADA THAT WAS EVIDENT IN VISIBLE SATELLITE IMAGERY
YESTERDAY SHOULD BE FIRMLY OVERHEAD TODAY AND COULD MITIGATE
INSOLATION. GIVEN THE ARGUMENTS ON BOTH SIDES...HAVE GONE WITH A
MAX TEMP FORECAST ABOVE GUIDANCE BUT NEAR YESTERDAYS LEVELS...OR
AROUND A DEGREE COOLER IN SOME AREAS. IN ANY EVENT IT WILL BE NEAR
OR BELOW NORMAL FOR THE SEASON AND OVERALL A VERY PLEASANT DAY FOR
MOST OUTDOOR ACTIVITIES.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 310 AM CDT WED JUL 9 2014

LONG TERM FORECAST PERIOD BEGINS WITH ANOMALOUSLY DEEP TROF
CONTINUING OVER EASTERN U.S./CANADA. ENERGY COMING ASHORE ACROSS
WESTERN CANADA WILL HELP PUSH THE TROF EASTWARD...ALLOWING RETURN
FLOW TO COMMENCE OVER THE HIGH PLAINS. COMBINATION OF RETURN FLOW
AND SYNOPTIC FORCING OWING TO A SOUTHEAST-MOVING H5 SHORTWAVE WILL
HELP FACILITATE SHRA/TSRA DEVELOPMENT TONIGHT ACROSS
NE/KS...HOWEVER THAT CONVECTION IS EXPECTED TO STAY WEST OF THE
CWA AS IT SLIDES SOUTHEAST.

GUIDANCE HAS BEEN TRENDING SLOWER ON THE THURSDAY NIGHT H5
SHORTWAVE TO IMPACT OUR CWA. THIS SHORTWAVE...IN ADVANCE OF THE
STRONGER H5 TROF ACROSS WESTERN CANADA...IS NOW PROGGED TO SLIDE
SOUTHEAST ACROSS OUR CWA LATE THURSDAY NIGHT OR EARLY FRIDAY
MORNING. THERMODYNAMIC AND KINEMATIC FORCING ARE EXPECTED TO BE
SUFFICIENT TO BRING SHRA/TSRA TO MUCH OF THE CWA. SEVERE WEATHER
POTENTIAL IS LOOKING LESS FAVORABLE...HOWEVER...WITH MUCAPES
TRENDING LOWER. CLOUD LAYER SHEAR PARAMETERS DO SUGGEST THE
POTENTIAL FOR SOME HAIL...WITH SOME POSSIBLE ISOLATED INSTANCES OFHAIL
THAT REACHES SVR CRITERIA OF 1 INCH OR LARGER IN DIAMETER.

PRECIP CHANCES RETURN FRIDAY NIGHT INTO SATURDAY AS A WEAK H5
RIPPLE AND ASSOCIATED SFC BOUNDARY MOVE OVER THE REGION. AMPLE
MOISTURE IS EXPECTED TO BE AVAILABLE AS LLJ KICKS IN AGAIN. AS
WITH THE THURSDAY NIGHT EVENT...AM NOT OVERLY CONCERNED ABOUT SVR
POTENTIAL DUE TO RELATIVELY LOW MUCAPE AND SHEAR VALUES.

PCPN CHANCES CONTINUE THROUGH THE WEEKEND AS THE SFC BOUNDARY
STALLS OUT ACROSS THE CWA...LIKELY ACROSS THE SOUTHERN CWA NEAR
THE IA/MO BORDER. A STRONGER H5 SHORTWAVE IS PROGGED TO ROTATE
AROUND THE SOUTHERN CANADA H5 TROF BY LATE WEEKEND...BRINING A
REINFORCING BOUNDARY AND PUSHING BOTH SOUTH OF THE CWA BY EARLY
NEXT WEEK. BY THAT TIME...MODELS ARE SUGGESTING THAT SOUTHERN
CANADA H5 TROF WILL CLOSE OFF TO ANOMALOUSLY LOW HEIGHTS AND BE
CENTERED INVOF THE NORTHERN GREAT LAKES. THIS SOLUTION HAS BEEN
FACTORED INTO THE END OF THE LONG TERM PERIOD...WHICH SUGGESTS
THE POTENTIAL FOR BELOW NORMAL TEMPERATURES.

&&

.AVIATION...09/12Z
ISSUED AT 621 AM CDT WED JUL 9 2014

MAINLY VFR CONDITIONS WILL PREVAIL WITH LIGHT WINDS AND NO PRECIP
THROUGH THE TAF PERIOD...HOWEVER THERE IS ONE BIG CAVEAT.
WILDFIRES ACROSS NORTHERN CANADA ARE PRODUCING A LARGE SMOKE PLUME
THAT HAS SPREAD INTO NORTH DAKOTA...AND WITH NORTHWEST FLOW ALOFT
AND A SURFACE HIGH PRESSURE RIDGE BUILDING DOWN ACROSS IOWA TODAY
THERE IS A POSSIBILITY THAT THE SMOKE COULD LEAD TO VSBY
RESTRICTIONS AT OUR TERMINALS ESPECIALLY THIS AFTN AND EVE. AT
THIS TIME CONFIDENCE IS LOW...SO HAVE ADVERTISED ONLY 6SM HZ.
HOWEVER...UPSTREAM OBS WILL NEED TO BE WATCHED TODAY IN CASE LOWER
VSBYS MAKE THEIR WAY THIS FAR SOUTH.

&&

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

&&

$$

SHORT TERM...LEE
LONG TERM...ZOGG
AVIATION...LEE


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