Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 212343
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
643 PM CDT TUE OCT 21 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 349 PM CDT TUE OCT 21 2014

RIDGE WILL CONTINUE TO PUSH EASTWARD OVERNIGHT. WINDS WILL SHIFT TO
THE SOUTH. MOISTURE WILL INCREASE AHEAD OF APPROACHING FRONTAL
BOUNDARY WITH SOUTHERLY SURFACE FLOW. INSTABILITY INCREASES...AND
MODELS ATTEMPT TO BRING PRECIPITATION TO THE NEAR 12Z.
HOWEVER...GIVEN AMOUNT OF DRY AIR AT MID AND UPPER LEVELS...HAVE
OPTED FOR DRY FORECAST. LOW LEVEL MOISTURE INCREASING MAY ALLOW FOR
FOG DEVELOPMENT...THOUGH WITH WINDS INCREASING HAVE LEFT FOG MENTION
OUT AS WELL. WAA WILL ALSO INCREASE FROM WEST TO EAST...HELPING TO
KEEP TEMPERATURES UP...AS WELL AS WITH INCREASING CLOUDS...AND HAVE
KEPT TEMPERATURES WARMER THAN PREVIOUS NIGHT...THOUGH MAY STILL BE
TOO WARM.

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
ISSUED AT 349 PM CDT TUE OCT 21 2014

PRECIPITATION CHANCES LATE WEDNESDAY THROUGH EARLY THURSDAY AND
TEMPERATURES THROUGH THE WEEKEND ARE THE PRIMARY FORECAST
CHALLENGES FOR THE PERIOD. MAIN PV ANOMALY IS CURRENTLY CENTERED
FROM WESTERN MONTANA THROUGH IDAHO. THIS SYSTEM WILL SHIFT
GENERALLY EAST AND MOVE THROUGH THE DAKOTAS ON WEDNESDAY AND INTO
MINNESOTA WEDNESDAY NIGHT. A MID LEVEL SHORT WAVE CURRENTLY OVER
ERN COLORADO WILL LIFT NORTHEAST AS THE AFOREMENTIONED PV ANOMALY
SHIFTS EAST. THIS SYSTEM WILL LIFT BEGIN TO BRING KINEMATIC
FORCING ACROSS WESTERN IOWA BY LATE WEDNESDAY. IN
ADDITION...THETA-E ADVECTION WILL MOVE ACROSS IOWA IN 2 SURGES
WITH THE FIRST ARRIVING MID DAY WEDNESDAY AND THE OTHER BY
WEDNESDAY EVENING. THE INITIAL SURGE SHOULD BRING SOME CLOUD
COVER TO THE STATE AND LIKELY ENOUGH TO LIMIT TEMPERATURES DURING
THE AFTERNOON. THEREFORE HAVE BACKED HIGH TEMPERATURES DOWN A FEW
DEGREES. THE SECOND SURGE WILL BE THE ARRIVAL OF GULF MOISTURE.
THE MOISTURE PLUME MOVING ACROSS THE STATE WILL BE ALONG A NARROW
RIBBON. THE COMBINATION OF THE THETA-E ADVECTION AND SOME RESIDUAL
KINEMATIC FORCING SHOULD LEAD TO A THIN LINE OF PRECIPITATION
MOVING EAST ACROSS THE STATE WEDNESDAY NIGHT.

MUCH OF THE PRECIPITATION IS EXPECTED TO BE OVER EASTERN IOWA BY
THURSDAY MORNING...THEN DRY AIR ARRIVES AS HIGH PRESSURE ARRIVES.
THIS SHOULD LEAD TO GOOD VIEWING CONDITIONS FOR THE PARTIAL SOLAR
ECLIPSE LATE THURSDAY AFTERNOON. THE THERMAL RIDGE WILL BECOME
ESTABLISHED ACROSS IOWA FRIDAY THROUGH THE WEEKEND IN WHAT LOOKS
TO BE AN OUTSTANDING THREE DAYS. HIGH TEMPERATURES IN THE 60S AND
70S ARE EXPECTED. SUNDAY SHOULD BE THE WARMEST DAY WITH THE
PRESSURE GRADIENT INCREASING AS THE HIGH PRESSURE DEPARTS TO THE
EAST AND LOW PRESSURE MOVES INTO THE WESTERN PLAINS. A FEW AREAS
LIKELY WILL REACH THE UPPER 70S BY SUNDAY AFTERNOON. A FRONTAL
BOUNDARY WILL MOVE THROUGH EARLY NEXT WEEK AND WILL BRING ANOTHER
CHANCE FOR PRECIPITATION MONDAY AND MONDAY NIGHT ALONG WITH COOLER
CONDITIONS WITH HIGHS SETTLING BACK INTO THE 50S BY TUESDAY.

&&

.AVIATION...21/00Z
ISSUED AT 643 PM CDT TUE OCT 21 2014

VFR CONDITIONS ARE ANTICIPATED THROUGH THE PERIOD...ALTHOUGH THERE
ARE A FEW CONCERNS. SKIES WILL BE CLEAR INITIALLY HOWEVER LOW END
VFR CIGS MAY DEVELOP EARLY WED MORNING ALONG WITH THE POSSIBILITY
OF BRIEF MVFR FOG EAST AS MOISTURE BEGINS TO INCREASE. THERE IS
ALSO THE POTENTIAL FOR SOME SHOWERS EARLY WED...BUT WILL LIKELY
MAINLY BE VIRGA. NO MENTION FOR THE MOMENT.

&&

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

&&

$$

SHORT TERM...AWB
LONG TERM...DONAVON
AVIATION...SMALL



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