Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 221734
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1234 PM CDT WED OCT 22 2014

.SYNOPSIS...
ISSUED AT 618 AM CDT WED OCT 22 2014
LOW PRESSURE TROUGH FROM CENTRAL ND INTO THE TX PANHANDLE WILL
MOVE INTO IA LATER TONIGHT AND EAST ON THURSDAY. PACIFIC HIGH
PRESSURE WILL BUILD INTO THE UPPER MIDWEST FOR FRIDAY THROUGH MUCH
OF THE WEEKEND.

&&

.UPDATE...
ISSUED AT 634 AM CDT WED OCT 22 2014

AN UPDATE WILL BE OUT SHORTLY TO TAKE IN TO ACCOUNT SPRINKLES THAT
HAVE DEVELOPED IN THE WAA BAND OF CLOUDS OVER WESTERN IA.

&&

.SHORT TERM /TODAY/...
ISSUED AT 343 AM CDT WED OCT 22 2014

HIGH PRESSURE RIDGE HAS MOVE EAST OF THE MISSISSIPPI RIVER WITH A
SOUTHEAST FLOW OVER THE CWA TODAY. STRONG THETA-E ADVECTION IS
TAKING PLACE THIS MORNING AND IS EVIDENT IN THE CLOUD FIELD ON
SATELLITE THIS MORNING OVER WESTERN IA. THIS FITS WELL WITH THE
MODELS DEPICTION. OPTED TO IGNORE THE VERY LIGHT PRECIPITATION
MODELS SHOW WITH THE BAND OF THETA-E ADVECTION...FEELING THE LOWER
LEVELS WILL BE TOO DRY FOR THAT THIS MORNING. TEMPERATURES WILL BE
TRICKY. THOUGH H8 TEMPS ARE ON THE RISE...CLOUDS WILL PLAY A
FACTOR WITH THE WEAK LATE OCT SUN. WILL GO CLOSE TO A DEGREE OR
TWO BELOW YESTERDAY. HIGH OCTANE AIR FOR OCTOBER IS TO THE WEST OF
THE STATE WITH PWAT VALUES RIDING TO 1.25 INCHES OR MORE. PRECIP
IS LIKELY TO SLIP INTO THE FAR WESTERN COUNTIES LATE IN THE DAY
TODAY. WENT WITH SHOWERS AND ISOLATED THUNDER. DO NOT THINK THE
THUNDER IS VERY LIKELY, BUT WOULDN`T RULE OUT A CRACK OF THUNDER
HERE AND THERE.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 343 AM CDT WED OCT 22 2014

PRIMARY FORECAST FOCUS REMAINED ON RAIN CHANCES TONIGHT INTO
THURSDAY MORNING...AND WITH TEMPERATURES OVER THE WEEKEND. LEANED
TOWARD A BLEND OF THE NAM12/SREF AND NMM/ARW FOR TIMING OF PRECIP
TONIGHT INTO THURSDAY...THEN TOWARDS THE ECMWF FRIDAY THROUGH
EARLY NEXT WEEK.

TONIGHT INTO THURSDAY...CLIPPER SYSTEM QUICKLY MOVES ACROSS THE
REGION TONIGHT AND EXITS THE STATE A BIT SOONER THAN PREVIOUSLY
FORECAST...AT LEAST THE BULK OF THE FORECAST AREA. STILL DEEP
MOISTURE TRANSPORT AND GOOD THETA-E ADVECTION INTO CENTRAL IOWA
TONIGHT AHEAD OF THE FRONT. STRONGEST FORCING ENTERS THE WESTERN
EDGES OF THE FORECAST AREA B/T 00-03Z THURSDAY BEFORE
TRANSITIONING EAST B/T 03Z TO 09Z THURSDAY. THE PRECIP LOOKS TO
QUICKLY EXIT THE SOUTHEAST BY 18Z AT THE LATEST. CUT BACK ON POPS
ACROSS THE NORTHEAST B/T 15-18Z THURSDAY WITH THE QUICKER MODEL
SOLUTIONS. STILL LOOKING AT A DECENT AMOUNT OF RAINFALL WITH
PRECIPITABLE WATER VALUES TOPPING 1.00 TO 1.25 INCHES TONIGHT.

FRIDAY THROUGH SUNDAY...500MB RIDGE GRADUALLY SHIFTS EASTWARD
FRIDAY INTO SATURDAY AND BY SUNDAY LOOKS TO BE CENTERED OVER THE
MISSISSIPPI VALLEY. A WEAK SHORTWAVE RIDING THE UPPER RIDGE WILL
RAPIDLY MOVE ACROSS THE STATE ON FRIDAY AND BRING A LITTLE MORE
CLOUD COVER AND A WESTWARD WIND SHIFT BY THE AFTERNOON. NOT
ENOUGH TO GO ANY COOLER THAN PREVIOUSLY FORECAST HOWEVER. SUNDAY
STILL LOOKS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD WITH
STRONG SOUTHWEST FLOW AT THE SURFACE AND ALOFT. 850MB TEMPS WARM
TO +14C TO +16C AND WITH VERY GOOD MIXING TO NEAR 900MB.

MONDAY AND TUESDAY...GFS AND ECMWF BOTH DEPICTING A LONGWAVE
TROUGH MOVING INTO THE CENTRAL U.S. BY MONDAY INTO
TUESDAY...WITH THE ECMWF SLIGHTLY DEEPER. PRECIP CHANCES LOOK TO
BE MONDAY NIGHT INTO TUESDAY.

&&

.AVIATION...22/18Z
ISSUED AT 1234 PM CDT WED OCT 22 2014

VFR CONDITIONS WILL PREVAIL INTO THIS EVENING BEFORE A BAND OF LOW
CLOUDS AND SHRA MOVE INTO THE AREA FROM WESTERN IOWA. THIS BAND
WILL PROGRESS STEADILY OVER THE TERMINALS OVERNIGHT...CLEARING OUT
AFTER SUNRISE THURSDAY MORNING. PRIMARY FORECAST CHALLENGE IS THE
EXTENT TO WHICH CIGS/VSBYS WILL FALL WITHIN THE BAND OF
CLOUDS/SHRA. FORECAST SOUNDINGS ARE DIRE WITH IFR CIGS
INDICATED...HOWEVER UPSTREAM RADAR RETURNS AND SURFACE OBS ARE
SHOWING THAT THE MODELS HAVE BEEN OVERLY PESSIMISTIC TO THIS POINT
SO MVFR MAY BE MORE THE RULE. FOR NOW HAVE ADVERTISED MVFR
CONDITIONS OVERNIGHT IN THE 18Z TAFS...BUT THIS WILL NEED TO BE
REASSESSED FOR THE 00Z AND 06Z ISSUANCES.

&&

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

&&

$$

UPDATE...MS OCT 14
SYNOPSIS...MS OCT 14
SHORT TERM...MS OCT 14
LONG TERM...PODRAZIK
AVIATION...LEE



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