Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 231741
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1241 PM CDT WED APR 23 2014

.SHORT TERM /TODAY/...
ISSUED AT 322 AM CDT WED APR 23 2014

MAIN CHALLENGES TODAY WILL BE TEMPERATURES...WIND AND PRECIPITATION.
THOUGH MOISTURE IS SOMEWHAT LIMITED AT THE MOMENT AT H850...MODELS
HAVE CONTINUE TO NAIL CONVECTION THAT IS DEVELOPING ACROSS
NORTHEASTERN KS EARLY TODAY ALONG SFC WARM FRONT AND LEADING EDGE OF
STRONGER WIND FIELDS/MOISTURE CHANNEL ALOFT. SOME MOISTURE HAS MADE
IT BACK TO EASTERN OK... AND SUSPECT THAT THIS IS THE SOURCE OF
CURRENT CONVECTION. THIS WILL DRIVE NORTHEAST WITH TIME TODAY AND
FILL IN OVER OUR AREA BETWEEN 12-18Z AS THETAE ADVECTION INCREASES
THROUGH MID MORNING. BEST FORCING WILL MOVE NORTHEAST WITH TIME
THROUGH NORTHEAST SECTIONS OF FORECAST AREA BY LATE AFTERNOON...BUT
SOME LINGERING SHOWERS WILL REMAIN SW INTO CENTRAL SECTIONS PRIOR TO
MAIN SHORT WAVE EXPECTED TO MOVE ACROSS THE REGION TONIGHT/THURSDAY.
TEMPERATURE FORECAST TODAY SOMEWHAT CHALLENGING...STARTING DAY MILD
WITH TEMPS IN THE 40S TO LOWER 50S SOUTH...BUT SUSTAINED EAST
SOUTHEASTERLY FLOW THROUGH A GOOD SHARE OF THE DAY NORTH OF THE WARM
FRONT SOUTH OF US TODAY WILL CAP HIGHS IN THE 60S SOUTH AND 50S
NORTH. SHOWER ACTIVITY WILL FURTHER PREVENT ANY RAPID WARMING DUE TO
EVAP COOLING DURING THE DAY. FORECAST MUCAPE VALUES TODAY NEARLY NIL
ACROSS THE AREA AND WILL TRIM ISO THUNDER BACK TO SHOWERS DUE TO DRY
AIRMASS IN PLACE AT THIS TIME. GRADIENT WINDS WILL PICK UP TODAY
ESPECIALLY ACROSS THE WEST. BY LATE MORNING...SOUTHEAST WINDS LOOK
TO BE NEARING OR JUST ABOUT 30 MPH OVER THE FAR WEST/NORTHWEST
THROUGH MOST OF THE AFTERNOON. WILL ISSUE WIND ADV FOR SMALL PORTION
OF THE WESTERN FORECAST AREA TODAY.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 322 AM CDT WED APR 23 2014

STILL DEALING WITH THE TWO MAIN SYSTEMS TONIGHT INTO THURSDAY AND
THEN THE NEXT ONE SATURDAY NIGHT INTO EARLY NEXT WEEK. INITIALLY
THIS EVENING EXPECT AN EXITING AREA OF SHOWERS TO THE EAST...WITH
THE NEXT MORE ROBUST ROUND OF PRECIP EXPECTED BY LATE EVENING INTO
THE OVERNIGHT HOURS. STRONG THETA-E ADVECTION/WAA SETTING UP ACROSS
THE AREA...WITH MOISTURE TRANSPORT VERY IMPRESSIVE AND DIRECTED
RIGHT INTO CENTRAL IA BY 06-09Z THURSDAY. EXPECT SHOWER/THUNDERSTORM
DEVELOPMENT ACROSS NORTHERN HALF OF THE CWA THIS EVENING ON THE NOSE
OF THE THETA-E RIDGE...WITH MORE WIDESPREAD ACTIVITY BY LATE EVENING
INTO THE OVERNIGHT HOURS...AS THE LINE OF CONVECTION EXPECTED TO
FIRE TO THE WEST LATER TODAY PUSHES EASTWARD THROUGH THE CWA AS THE
SFC LOW SLIDES INTO CENTRAL IA BY AROUND SUNRISE THURSDAY. AS THE
ENTIRE SYSTEM SHOVES EAST THURSDAY...EXPECT PRECIP TO TAPER OFF FROM
WEST TO EAST THROUGH THE LATE MORNING/EARLY AFTERNOON HOURS. DRY
CONDITIONS THEN STILL EXPECTED FOR THURSDAY NIGHT INTO FRIDAY. WEAK
WAA WITH H85 TEMPS AROUND +10C TO +12C ACROSS THE AREA SHOULD ALLOW
FOR A PRETTY DECENT SPRING DAY ACROSS THE AREA.

ATTENTION THEN SHIFTS TOWARD THE LATE WEEKEND SYSTEM...WITH A VERY
POTENT SYSTEM DIGGING INTO THE INTERMOUNTAIN WEST BY SATURDAY. UPPER
LEVEL SYSTEM TO CLOSE OFF AND BECOME NEARLY STACKED TOWARD
SUNDAY...WITH THE MAIN CIRCULATION MOVING VERY SLOWLY FROM SE CO AT
12Z SUNDAY TO SOUTH CENTRAL NE BY 12Z MONDAY. THIS PLACES THE STATE
IN AN ACTIVE SOUTHWESTERLY FLOW PATTERN ALOFT...WITH IMPULSES ALOFT
EJECTING OUT AHEAD OF THE MAIN UPPER LOW. THIS SHOULD BRING ROUNDS
OF PRECIPITATION CHANCES TO MUCH OF THE STATE BEGINNING SATURDAY
NIGHT...AND CONTINUING INTO EARLY NEXT WEEK. HARD TO NAIL DOWN THE
TIMING OF THESE IMPULSES...THEREFORE HAVE SOME BROADBRUSH HIGH
CHANCE/LIKELY POPS ACROSS THE ENTIRE CWA FROM SATURDAY NIGHT THROUGH
MONDAY NIGHT. MODELS THEN SHOVE THE SYSTEM EAST INTO THE OHIO VALLEY
REGION WITH BROAD UPPER LEVEL TROUGHING ACROSS THE CENTRAL/EASTERN
US AND LET THE CIRCULATION SPIN THERE FOR A FEW MORE DAYS. THEREFORE
EXPECT AN OVERALL COOLER PERIOD INTO TUESDAY AND THE MIDDLE OF NEXT
WEEK...WITH POSSIBILITY OF ADDITIONAL CHANCES OF PRECIPITATION
WRAPPING BACK INTO THE CWA. OVERALL MODELS IN BETTER AGREEMENT WITH
THE GENERAL TREND WITH THIS SYSTEM...AND THEREFORE CERTAINTY IS HIGH
THAT SHOULD SEE SOME SORT OF LONG DURATION PRECIPITATION EVENT FOR
THE STATE ESPECIALLY SUNDAY INTO MONDAY. IT IS THE FINER DETAILS
THAT STILL REMAIN QUITE UNCERTAIN...INCLUDING HOW MUCH COLD AIR WILL
WRAP INTO THE BACKSIDE OF THIS SYSTEM. EC IS MUCH COLDER...THAN THE
CANADIAN/GFS AT THIS TIME. HAVE LEFT ALL PRECIP MENTION IN LIQUID
FORM...BUT IF THE EC VERIFIES COULD HAVE SOME SNOW MIXING WITH THE
RAIN OR A BRIEF CHANGEOVER TO ALL SNOW BY MONDAY NIGHT ACROSS
PORTIONS OF THE CWA.

&&

.AVIATION...23/18Z
ISSUED AT 1237 PM CDT WED APR 23 2014

AREA OF SHRA WITH ISOLATED TSRA WILL CONTINUE TO PUSH EAST ACROSS
SITES THROUGH THE AFTERNOON. HOWEVER...CONDITIONS WILL REMAIN
PRIMARILY VFR THOUGH MAY DROP TO MVFR AT TIMES WITH SHRA. WINDS
WILL BE STRONG AND GUSTY FROM THE SOUTHWEST. WILL LIKELY SEE A
BRIEF PERIOD OF DRY BEFORE ADDITIONAL TSRA AND SHRA IS POSSIBLE
OVERNIGHT...PUSHING EASTWARD...AFFECTING WESTERN
SITES...KFOD...FIRST. WILL SEE VISIBILITIES AND CEILINGS DROP TO
MVFR OR IFR AT TIMES WITH PRECIPITATION. HAVE TRENDED THIS WAY FOR
NOW...WITH LOW CEILINGS AND VISIBILITIES LINGERING THROUGH
PERIOD. WINDS WILL REMAIN STRONG AND GUSTY THROUGH PERIOD.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 PM CDT THIS EVENING FOR CALHOUN-CARROLL-
CRAWFORD-EMMET-PALO ALTO-POCAHONTAS-SAC.

&&

$$

SHORT TERM...REV
LONG TERM...BEERENDS
AVIATION...AWB



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