Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 232048
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
348 PM CDT THU APR 23 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 217 PM CDT THU APR 23 2015

HIGH PRESSURE WILL CONTINUE TO PUSH SOUTHEAST FOR THE BEGINNING OF
THE PERIOD. THIS WILL HELP TO KEEP CONDITIONS DRY AND WINDS LIGHTER.
THIS MIGHT ALLOW FOR TEMPERATURES TO QUICKLY DROP IN THE EAST. HAVE
THEREFORE DROPPED TEMPERATURES SLIGHTLY IN THE EAST...AND ELSEWHERE.
GIVEN AMOUNT OF DRY AIR...MAY BE TOO WARM ON TEMPERATURES WHICH
COULD ALLOW FOR TEMPERATURES TO DROP BELOW FREEZING IN THE EAST.
HOWEVER...WITH RETURN OF CLOUDS AND WAA AND INCREASING WINDS AHEAD
OF A BOUNDARY WHICH WILL ENTER WESTERN IOWA NEAR 12Z...DO NOT HAVE
HIGH CONFIDENCE IN FREEZING TEMPERATURES TO ISSUE FREEZE OR FROST
HEADLINES...THOUGH WILL NEED TO BE MONITORED.

BOUNDARY WILL PUSH EAST WHICH WILL BRING INCREASING CLOUDS AND
MOISTURE. MODELS ARE A BIT SLOWER ON THE PROGRESSION OF THE
BOUNDARY...AND FEEL THEY DO NOT HAVE A GOOD HANDLE ON CURRENT DRY
AIR. THEREFORE...BELIEVE DRY AIR WILL HELP TO KEEP ONSET OF
PRECIPITATION DELAYED...AND HAVE PUSHED BACK ONSET TO CLOSER TO 12Z.
ENOUGH MID LEVEL INSTABILITY TO WARRANT ISOLATED THUNDER MENTION
OVERNIGHT AS WELL. WITH COLDER TEMPERATURES IN THE NORTH MAY SEE A
RAIN/SNOW MIX IF PRECIPITATION PUSHES FAR ENOUGH EAST...THOUGH WILL
LEAVE MENTION OUT ATTM AS BELIEVE TEMPERATURES WILL BE WARM ENOUGH
FOR RAIN WHEN PRECIPITATION STARTS.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 217 PM CDT THU APR 23 2015

THE WEEKEND WILL BE A WET ONE ACROSS THE CWA WITH A COUPLE OF
ROUNDS OF PRECIPITATION. THE FIRST WILL BE IN THE REGION EARLY FRIDAY
AND WILL BE DRIVEN INITIALLY BY GOOD WAA/THETA-E
ADVECTION...PRIMARILY ABOVE THE SURFACE AROUND 850MB...AND QUICKLY
FOLLOWED BY A VORT MAX FROM A SHORT WAVE MOVING THROUGH AHEAD OF
THE IMPENDING LOW PRESSURE SYSTEM. INITIAL PRECIPITATION WILL BE
ON THE LIGHT SIDE FROM THE MORE GRADUAL LIFT OF THE WAA AND
LIKELY HEAVIER WHEN THE VORT MAX AND BOUNDARY MOVES THROUGH A
SHORT WHILE LATER. THE POSSIBILITY OF ISOLATED STORMS ARE
POSSIBLE WITH A LITTLE BIT OF ELEVATED CAPE...BUT WAS HELD OUT OF
THE FORECAST FOR THE TIME BEING GIVE ITS UNDERWHELMING NATURE.

EARLY SATURDAY WILL BEGIN THE SECOND ROUND OF PRECIPITATION AND
WILL BE DRIVEN BY A LOW PRESSURE SYSTEM THAT IS CURRENTLY WORKING
ITS WAY OFF THE ROCKIES AND INTO KANSAS. THE LOW SHOULD PASS JUST
SOUTH OF IOWA AND MAY CLIP SOUTHEAST IOWA AS IT PASSES. THUNDERSTORMS
WILL BE POSSIBLE AND EVEN LIKELY IN THE SOUTHERN THIRD OF THE
STATE SATURDAY MORNING AND INTO THE AFTERNOON WITH ELEVATED CAPE
VALUES AROUND 1000J/KG AND MARGINAL SHEAR. WHILE WIDESPREAD SEVERE
STORMS ARE NOT EXPECTED...A FEW MAY BE SEVERE WITH THE PRIMARY
CONCERN BEING HAIL AND WINDS. THE REST OF THE STATE WILL BE
COOL...IF NOT COLD...AND DREARY AS THEY CONSTANT OVERCAST SKIES
AND PRECIPITATION WHILE SITTING IN THE WRAP AROUND SECTION OF THE
LOW AND SHOULD REMAIN SO FOR MUCH OF THE DAY. TOTALS MAY EASILY
EXCEED AN INCH ON SATURDAY...ESPECIALLY IN THE SOUTH WHERE STORMS
MAY BE PRESENT.

AFTER THE LOW QUICKLY EXITS THE REGION LATE SATURDAY AND INTO
SUNDAY...A SURFACE RIDGE WILL SET IN AND CLEAR SKIES OUT SUNDAY
AND INTO THE EARLY WORK WEEK. SURFACE FLOW WILL BE WEAK AND
GENERALLY OUT OF THE NORTHEAST THROUGH MIDWEEK...HELPING KEEP THE
TEMPERATURES SEASONABLE AND IN THE 60S. MIDWEEK THE MODELS
CONTINUE TO HOLD ONTO A WEAK UPPER LEVEL TROUGH THAT SHOOTS SOUTH
THROUGH WESTERN IOWA LATE TUESDAY AND MAY PROVIDE A QUICK SHOT OF
CLOUDS AND LIGHT PRECIPITATION...BUT THE PRECIPITATION LOOKS
UNLIKELY AT THIS POINT. BY THURSDAY WE SHOULD FINALLY GET SITUATED
UNDERNEATH A RIDGE RATHER THAN SITTING IN NORTHWEST FLOW AS HAS
BEEN COMMON OF LATE. WITH THE RIDGE OVERHEAD...SOUTHERLY FLOW WILL
RETURN AND TEMPERATURES SHOULD BEGIN TO CLIMB BACK INTO THE 70S
AND POSSIBLY BEYOND FOR THE WEEKEND.

&&

.AVIATION...23/18Z
ISSUED AT 1233 PM CDT THU APR 23 2015

HIGH PRESSURE WILL KEEP CONDITIONS VFR FOR BEGINNING OF PERIOD.
WINDS WILL BE LIGHT AND VARIABLE...BECOMING SOUTHERLY NEAR 00Z.
BOUNDARY WILL PUSH EAST INTO WESTERN IOWA BY END OF PERIOD WITH
WINDS INCREASING. SHRA WILL BE POSSIBLE AT WESTERN SITES KFOD/KDSM
BY END OF PERIOD. WITH SHRA MAY SEE MVFR OR LOWER CEILINGS AND
VISIBILITIES THOUGH HAVE NOT INCLUDED MENTION ATTM DUE TO
UNCERTAINTIES IN TIMING.


&&

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

$$

SHORT TERM...AWB
LONG TERM...CURTIS
AVIATION...AWB



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