Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 280958
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
358 AM CST WED JAN 28 2015

.SHORT TERM /TODAY/...
ISSUED AT 355 AM CST WED JAN 28 2015

COMPLICATED FORECAST TODAY TO SAY THE LEAST.  INTENSE LOW EAST OF
MAINE CONTINUES TO BE HOLDING BACK EASTWARD TRANSLATION OF THE UPPER
LEVEL RIDGE OVER THE MIDWEST TODAY...RESULTING IN LOW STRATUS CLOUDS
HOLDING ON OVER EASTERN IOWA YESTERDAY AFTERNOON. FAST FORWARD TO
CURRENT WITH LOW STRATUS AND LIGHT FOG EXPANDING WEST A BIT INTO
CENTRAL IOWA ALONG A WEAK FRONTAL BOUNDARY EXTENDING WEST TO EAST
OVER THE FORECAST AREA AT 08Z. MESOSCALE MODELS DOING A BETTER JOB
WITH CLOUDS THAN SYNOPTIC...HRRR CAPTURES THE EXPANSION AND
GENERALLY BEGINS TO MOVE THE DECK NORTHEAST DURING THE DAY AS THE
PLAINS LOW ENTERS IOWA THIS AFTERNOON. OVER THE NORTH...MOISTURE
WILL REMAIN FOR MUCH OF THE DAY SO CLOUDS AND MUCH COOLER
TEMPERATURES THIS AFTERNOON ARE LIKELY ACROSS THE NORTH. A WIDE
RANGE OF TEMPERATURES IS EXPECTED TODAY WITH HIGHS IN THE UPPER 30S
FROM MASON CITY TO WATERLOO TO THE MID 50S AT DES MOINES TO NEAR 60
OVER THE FAR SOUTH. WILL CONTINUE THE NEAR RECORD HIGH HEADLINE OVER
THE SOUTHWEST AS ONCE THE CLOUDS BACK OFF...TEMPERATURES SHOULD MOVE
UP RATHER QUICKLY LATER THIS MORNING AND EARLY AFTERNOON. BY MID TO
LATE AFTERNOON CLOUDS WILL BEGIN TO FILL IN AGAIN AS THE LOW BEGINS
TO INCREASE LIFT ACROSS THE REGION. BY LATE AFTERNOON PARTLY SUNNY
CONDITIONS TO CLOUDY SKIES WILL PREVAIL. WINDS WILL BE SOUTH
SOUTHEAST THIS AFTERNOON WITH THE STRONGER WINDS OVER SOUTHEAST
SECTIONS. DESPITE THE UNSEASONABLY WARM TEMPERATURES ALOFT...6C
NORTHEAST TO 14C SOUTHWEST BY MIDDAY COOLING TO 4C NORTHEAST TO 10C
SOUTH...AFTERNOON HIGHS WILL BE ADVECTION BASED RATHER THAN PURE
MIXING BASED. TOWARD SUNSET MOSTLY CLOUDY CONDITIONS ARE EXPECTED.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 355 AM CST WED JAN 28 2015

A VERY FAST MOVING SHORTWAVE IS STILL ON TRACK TO IMPACT DMX CWA
THURSDAY MORNING. AT 06Z WED...WATER VAPOR IMAGERY EASILY PICKING UP
THIS MID TO UPPER LOW CROSSING OVER THE ROCKIES. THE MODELS CONTINUE
TO INITIALIZE WELL WITH PLACEMENT OF THIS MID TO UPPER WAVE. TIMING
HAS REMAINED CONSISTENT...WITH THE MODELS PLACING THIS LOW DIRECTLY
OVER CENTRAL IOWA AT 06Z THU. SOUNDINGS ONCE AGAIN SHOW A SIZABLE
DRY AIR POCKET FROM AROUND 850MB TO 600MB WHICH WILL PREVENT CLOUD
THICKNESS FROM EXCEEDING 5 KFT AND...SUBSEQUENTLY...KEEP THIS SYSTEM
FROM PRODUCING ANYTHING BEYOND LIGHT PRECIP. KMCW TO KEST GFS
SOUNDINGS SUPPORT MAINLY DZ/-RA...WITH A VERY NARROW WINDOW OF -IP
TO -SN POSSIBLE FROM AROUND 09Z TO 12Z. BY 12Z THU...THIS LOW WILL
BE OVER NORTHERN ILLINOIS AND STRONG CAA ALONG WITH VERY DRY AIR IN
THE MID TO UPPER LEVELS WILL BE BROUGHT INTO OUR CWA. THOUGH A FAIR
AMOUNT OF SUNSHINE IS EXPECTED...DAYTIME TEMPS TO ONLY WARM AROUND 3
TO 5 DEGREES FROM OVERNIGHT MINS DUE TO CAA.

THURSDAY`S WINDS REMAIN WORTH MENTIONING. MODELS SHOWING 25 KT TO
30 KT WINDS RIGHT OFF THE DECK...APPROACHING 45 KT TO THE TOP OF
THE MIXED LAYER. SFC PRESSURE GRADIENT OF 3MB/100KM TO SUPPORT
STRONG WINDS AT THE SFC. WITH LOW OVER GREAT LAKES...WINDS WILL BE
STRONGEST ACROSS OUR NORTHERN CWA. IN ALL...WIND ADVISORY
BEGINNING EARLY THU AM LOOKING MORE AND MORE LIKELY WITH THE NEXT
UPDATE PACKAGE.

WHILE FRIDAY SHOULD BE SUNNY AND QUIET...IT LOOKS LIKE QUITE A
DIFFERENT STORY IS SHAPING UP FOR THE WEEKEND...ESPECIALLY
SATURDAY NIGHT INTO SUNDAY MORNING. THE EURO AND THE GFS ARE
BEGINNING TO COME IN LINE BOTH TEMPORALLY AND SPATIALLY WITH
BRINGING OUR NEXT CHANCE FOR "IMPACTFUL" SNOW ACCUMULATION TO OUR
CWA. FORECAST SOUNDINGS BEGIN TO SATURATE FROM TOP-DOWN SATURDAY
AFTERNOON. SEE LITTLE TO NO JUSTIFIABLE REASON FOR PRECIP DURING
THE MORNING SATURDAY...SO HAVE LOWERED POPS ACCORDINGLY. SATURDAY
EVENING...SOUNDINGS BEGIN TO COMPLETELY SATURATE ACROSS THE CWA
FROM SW TO NE...BECOMING COMPLETELY SATURATED BETWEEN 00Z SUN AND
06Z SUN. BOTH GFS AND EURO HAVE A LLJ TRANSPORTING MOISTURE INTO
THIS SYSTEM FROM THE GULF OF MEXICO. THE EURO IS SLIGHTLY FURTHER
NORTH WITH THIS MOISTURE...WHICH IS HELPING YIELD A COMPARATIVELY
HIGHER QPF. HIGHEST SNOWFALL AMOUNTS WILL THUS BE IN OUR SOUTHERN
CWA. CROSS SECTIONS CLEARLY SHOW LIFT THROUGH THE DENDRITIC GROWTH
ZONE. WAY TOO EARLY FOR ANY HEADLINES AT THIS POINT...BUT WORTH
NOTING THAT MODELS MAY BE KEYING IN ON A SOLUTION...WHICH WOULD
INCREASE CONFIDENCE.

BEHIND THIS SYSTEM...MONDAY INTO THE MID-WEEK...IT IS A LOCK THAT
TEMPERATURES WILL BE SIGNIFICANTLY COOLER THAN THEY HAVE BEEN FOR
THE PAST TWO WEEKS. THE FORECAST CHALLENGE FOR NOW IS HOW FAR THE
BOTTOM WILL FALL OUT ON TEMPS. ENSEMBLE RUNS ARE SHOWING AROUND -1
TO -2 STD DEV ON 850MB TEMPS ACROSS OUR CWA. TONIGHT`S 00Z GFS WAS
MARKEDLY COLDER THAN PVS RUNS. THE GFS HAS 850MB TEMPS DOWN TO
-19C ACROSS THE NE PORTION OF OUR CWA...WHEREAS THE EURO HAS 850
MB TEMPS DOWN TO ONLY -10C. SINCE OBVIOUS LACK OF CONSISTENCY FROM
GFS...WILL LEAN TOWARDS MORE CONSISTENT...LESS EXTREME...EURO. IF
THIS 00Z WED GFS SOLN HOLDS IN SUBSEQUENT RUNS...MAX AND MIN TEMPS
WILL NEED AT LEAST 5 DEGREES LOPPED OFF.

&&

.AVIATION...28/06Z
ISSUED AT 1140 PM CST TUE JAN 27 2015

IFR TO MVFR STRATUS EXPECTED TO IMPACT ALL SITES TONIGHT IN
ADDITION TO SOME VSBY RESTRICTIONS DUE TO FOG. CURRENTLY STRATUS
IS JUST EAST OF KFOD AND KDSM BUT SHOULD SHIFT SLIGHTLY WEST.
SOME BREAKS OVER THE SOUTH ON WEDNESDAY BUT STRATUS LIKELY WILL
LINGER NORTH. A FRONTAL BOUNDARY WILL BEGIN TO ARRIVE LATE
WEDNESDAY AND WILL BRING ANOTHER AREA OF IFR OR LOWER CIGS TO
NORTHERN IA BY 06Z. BREEZY SOUTHEAST WINDS BECOMING NW WITH FROPA
LATE.


&&

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

$$

SHORT TERM...REV
LONG TERM...KOTENBERG
AVIATION...DONAVON


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