Area Forecast Discussion
Issued by NWS Des Moines, IA

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738
FXUS63 KDMX 181150
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
652 AM CDT MON MAY 18 2015

.SYNOPSIS...
ISSUED AT 326 AM CDT MON MAY 18 2015

INTENSE LOW FOR MID MAY OVER NORTHERN MINNESOTA WILL MORE
NORTHEAST OUT OF THE AREA TODAY. HIGH PRESSURE OVER CENTRAL CANADA
WILL DROP SOUTH INTO THE DAKOTAS TONIGHT...SINKING SOUTH SLOWLY
AND REMAINING OVER THE CENTRAL U.S. THROUGH THE WEEK. AN UPPER
LEVEL SYSTEM WILL MOVE THROUGH THE CENTRAL U.S. WEDNESDAY.

&&

.SHORT TERM /TODAY/...
ISSUED AT 326 AM CDT MON MAY 18 2015

THE FORECAST PROBLEM TODAY WILL BE ONE OF WIND AND TEMPERATURES.  A
STRONG COLD FRONT WILL BE PUSHING ACROSS THE STATE AND HIGHS TODAY
WILL BE NOTABLY COLDER THAN WHAT WE HAVE BEEN SEEING OF LATE.  MOS
GUIDANCE IS SUGGESTING HIGHS IN THE LOW 50S TO LOW 60S ACROSS IOWA.
SOUNDINGS AND CURRENT OBS SHOW WINDS HAVING MORE OF A WESTERLY THAN
A NORTHERLY COMPONENT AND THIS COUPLED WITH THE LAST COLD SNAP BEING
NOT AS COLD AS WHAT GUIDANCE WAS SUGGESTING SO I RAISED MOST HIGHS
TODAY ABOVE WHAT MODEL BLENDS WERE PUTTING OUT.  THE EXCEPTION TO
THIS WAS ACROSS THE NORTH WHERE CLOUD COVER WILL HAMPER TEMPS.

WINDS WILL BE PROBLEMATIC AS WELL TODAY.  SUSTAINED WINDS TODAY WILL
BE FROM 15 TO 30 MPH WITH GUSTS AROUND 40 MPH OR SO.  THE STRONGEST
WINDS WILL BE ACROSS THE NORTHERN QUARTER OR THIRD OF IOWA.  HOWEVER
WITH CLOUD COVER PRESENT FOR A FAIR PART OF THE DAY IT DOES NOT
APPEAR THAT MAX MIXING POTENTIAL MAY BE REALIZED.  IT IS LIKELY THAT
A LOCATION OR TWO MAY BRIEFLY HIT ADVISORY CRITERIA BUT WIDESPREAD
ADVISORY CRITERIA IS NOT LIKELY.  WINDS SHOULD BE SIMILAR TO
YESTERDAY IN THAT SPOTS WILL HIT CRITERIA FROM TIME TO TIME BUT
SPEEDS SHOULD BE A LITTLE LESS THAN YESTERDAY.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 326 AM CDT MON MAY 18 2015

VERY COLD AIR IS IN PLACE OVER THE DAKOTAS WITH MODELS SHOWING
CURRENT H8 TEMPS IN THE -6 TO -8 C RANGE. SOME MODIFICATION AS IT
CONTINUES SOUTH...BUT THE POOL OF COOL AIR WILL BE WITH US THROUGH
A GOOD PART OF THE WORK WEEK. HIGH PRESSURE WILL DOMINATE THE
WEATHER THROUGH TUESDAY WITH A VERY COOL START ON TUESDAY. WILL
MENTION PATCHY FROST OVER NORTHERN IA...GENERALLY ALONG AND NORTH
OF U.S. HIGHWAY 30. DO NOT EXPECT SUB-FREEZING TEMPS...BUT A SMALL
WINDOW AROUND SUNRISE DECOUPLING TIME WILL GIVE THE POSSIBILITY OF
PATCHY FROST IN LOW LYING AREAS.

AS THE UPPER LEVEL SYSTEM MOVES IN TUESDAY NIGHT AND
WEDNESDAY...EXPECTED TO SEE A LARGE RAIN SHIELD DEVELOP IN THE WAA
ZONE AS SURFACE LOW PASSES SOUTH OF IOWA. THIS WILL MAKE FOR
TRICKY TEMPERATURES AND ACTUALLY AN INVERTED DAY WITH COOLEST
HIGHS IN THE SOUTH WHERE MORE CONTINUOUS RAINFALL IS MORE
LIKELY...AND HIGHEST OVER THE NORTH.

MODERATION IS ON TAP FOR THE REST OF THE WEEK. A STRONGER SYSTEM
WILL LIFT OUT FROM THE SOUTHWEST U.S. OVER THE WEEKEND. SOME
SIMILARITIES TO THE CURRENT SYSTEM...THOUGH DYNAMICS ARE NOT AS
STRONG AS THE CURRENT SYSTEM. ECMWF IS FARTHER SOUTH WITH THE
LOW. WOULD LEAN TOWARD THE EC SOLUTION...BUT THIS WILL NEED TO BE
MONITORED FOR SEVERE POTENTIAL...WHETHER IOWA GETS CLEANLY INTO
THE WARM SECTOR OR NOT.

&&

.AVIATION...18/12Z
ISSUED AT 652 AM CDT MON MAY 18 2015

MVFR CIGS ARE EXPECTED ACROSS NORTHERN TAF LOCATIONS WHILE REMAINDER
OF THE STATE WILL BE VFR.  W TO NW WIND AT 15 TO 25KTS WILL BE
COMMON WITH THE STRONGER WINDS ACROSS THE NORTH.  WIND GUSTS TO
35KTS ARE FCST THROUGH 21Z BEFORE DIMINISHING.

&&

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

$$

SYNOPSIS...MS MAY 15
SHORT TERM...FAB
LONG TERM...MS MAY 15
AVIATION...FAB



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