Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 221723
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1222 PM CDT TUE APR 22 2014

.SHORT TERM /TODAY/...
ISSUED AT 319 AM CDT TUE APR 22 2014

HIGH PRESSURE AND COOLER AIR SETTLING INTO THE AREA TODAY. SECONDARY
COLD FRONT JUST ENTERING NORTHERN IA AT 04Z THIS EVENING AND WILL
MOVE SOUTHEAST REMAINDER OF OVERNIGHT. COOLER AIR FROM MN/SD WILL
MOVE ACROSS THE REGION TODAY. ALOFT...POCKET OF H850 TEMPS OF 5C TO -
5C TO OUR NORTH...THOUGH TRAJECTORY WILL KEEP COOLEST AIR NORTHEAST
OF THE REGION AS THE HIGH BUILDS SOUTHEAST THROUGH IOWA TODAY. BUFR
SOUNDINGS SHOW DRY AIRMASS...BUT SHOULD BE ABLE TO PRODUCE A FEW
FAIR WX CLOUDS TODAY ACROSS THE REGION WITH SOME DAYTIME HEATING. BY
LATE AFTERNOON H850 TEMPS RECOVER TO 3C NORTHEAST TO ABOUT 5C WEST.
THIS SHOULD HELP PUSH HIGHS TO NEAR THE 60F MARK NORTHEAST AND THE
MID 60S ACROSS THE WEST. LIGHT NORTH WINDS WILL REMAIN IN THE
MORNING BUT THEN BECOME MORE SOUTHEAST OVER WESTERN SECTIONS BY LATE
DAY. OTHERWISE...UPSTREAM WAVE FOR WEDNESDAY EXPECTED TO THROW SOME
MID TO UPPER LEVEL CLOUDS BACK INTO THE REGION AS WEAK WARM FRONT
NOW OVER THE HIGH PLAINS THROUGH CENTRAL NE BEGINS TO PROVIDE SOME
RETURN LIFT THROUGH THE AFTERNOON HOURS.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 319 AM CDT TUE APR 22 2014

TWO MAIN PERIODS OF NOTE THROUGHOUT THE EXTENDED WITH THE FIRST
BEING WEDNESDAY INTO THURSDAY...AND THE SECOND OVER THE UPCOMING
WEEKEND INTO EARLY NEXT WEEK. INITIALLY WILL HAVE AN AREA OF SFC
HIGH PRESSURE SLIDING EAST TONIGHT WITH RETURN FLOW SETTING UP IN
ADVANCE OF AN AREA OF DEVELOPING LOW PRESSURE ALONG THE FRONT RANGE
OF THE ROCKIES IN RESPONSE TO AN UPPER TROUGH DIGGING INTO THE
INTERMOUNTAIN WEST. SOME THETA-E ADVECTION PUSHING INTO THE
WESTERN/NORTHERN CWA LATE TONIGHT...WITH MAJORITY OF MOISTURE
TRANSPORT IN THE LOW LEVELS ORIENTED MORE TO THE WEST/NORTH OF THE
CWA...AND JUST STARTING TO ANGLE INTO THE WESTERN CWA BY 12Z
WEDNESDAY. THEREFORE KEPT MAJORITY OF TONIGHT DRY WITH JUST
INCREASING CLOUD COVER...WITH THE EXCEPTION OF SOME SLIGHT CHANCE
POPS ACROSS THE FAR WEST LATE. EXPECT AN AREA OF LIGHT
SHOWERS/POSSIBLY ISOLATED THUNDER TO MOVE THROUGH THE NORTHERN CWA
WEDNESDAY MORNING IN AREA OF STRONGER THETA-E ADVECTION AND AS
MOISTURE TRANSPORT VECTORS BECOME ORIENTED INTO NORTH CENTRAL IOWA.
NAM TRYING TO SUGGEST DEVELOPMENT OF AN MCS ACROSS EASTERN NEBRASKA
LATE TONIGHT AND TRACKING IT EASTWARD INTO THE CENTRAL CWA
WEDNESDAY MORNING. GIVEN LOCATION OF THE BAROCLINIC ZONE AND HAVE
SOME SLIGHT CHANCE POPS ACROSS THE CENTRAL FOR THIS
POSSIBILITY...BUT EXPECT THE BETTER CHANCES TO BE WITH THE PUSH OF
MOISTURE ACROSS THE NORTH WEDNESDAY MORNING. EXPECT A BREAK FROM
ACTIVITY POSSIBLY IN THE AFTERNOON AS NEXT PUSH OF ENERGY ALOFT TO
SWING THROUGH LATER INTO WEDNESDAY EVENING/NIGHT WITH THE
DEVELOPMENT CLOSER TO THE SFC LOW CENTER/COLD FRONT CENTERED
ACROSS CENTRAL NE/WRN KS BY LATE WED AFTERNOON. SFC LOW TO LIFT
AND DEEPEN AS IT PUSHES INTO NW/CNTRL IA BY LATE WEDNESDAY NIGHT.
AS THE SFC TROUGH AXIS AND COOL FRONT SWING THROUGH AND THE ENERGY
ALOFT LIFTS THROUGH THE CWA...EXPECT GREATEST CHANCES FOR
WIDESPREAD SHOWER AND THUNDERSTORMS ACROSS THE CWA BY LATE
WEDNESDAY EVENING INTO THE OVERNIGHT HOURS. SYSTEM TO PUSH EAST OF
THE AREA THURSDAY...WITH LINGERING CHANCES OF SHOWERS/ISOLATED
THUNDER EXPECTED ACROSS THE CWA THURSDAY MORNING WITH PRECIP
CLEARING FROM WEST TO EAST BY THU AFTERNOON. DRY CONDITIONS THEN
EXPECTED THURSDAY NIGHT INTO FRIDAY AS HIGH PRESSURE BRIEFLY
BUILDS INTO THE STATE.

FOCUS THEN SHIFTS TO THE WEEKEND WITH THE LONG WAVE TROUGH EXPECTED
TO EJECT FROM THE WEST THROUGH THE CENTRAL US SATURDAY INTO MONDAY.
EC/GFS HAVE BEEN IN BETTER AGREEMENT...BUT IN THE LATEST MODEL SUITE
GFS BECOMING SLIGHTLY FASTER AND MORE AGGRESSIVE WITH THE SYSTEM
THAN THE EC/CANADIAN. UPPER TROUGH TO EJECT INTO THE CENTRAL PLAINS
SUNDAY BECOMING NEGATIVELY TILTED...WITH AN ASSOCIATED SFC LOW
BECOMING CENTERED AROUND THE KS/OK AREA WITH SOUTHERLY FLOW OUT
AHEAD OF THE SYSTEM INTO IOWA. MAIN WARM FRONT TO REMAIN TO THE
SOUTH OF THE STATE...WITH MAINLY ELEVATED OVERRUNNING SITUATION
OCCURRING ACROSS IOWA. BIGGEST ISSUE WILL BE THE STRONG
NORTHEASTERLY TO EASTERLY FLOW OF A LARGE AREA OF HIGH PRESSURE
SITUATED ACROSS THE GREAT LAKES. THIS WILL LIKELY CREATE A SHARP
CUTOFF ON THE NORTHERN/EASTERN EDGE OF AN PRECIPITATION AREA AND
WILL LIKELY DELAY ONSET OF THE PRECIPITATION AS IT WILL TAKE SOME
TIME TO SATURATE THE LOWEST LEVELS. THE EC/CANADIAN SHOWING A DRIER
SOLUTION WITH THE MAJORITY OF HEAVIER PRECIP EXPECTED TO REMAIN
SOUTH OF THE CWA CLOSER TO THE SFC WARM FRONT. THEREFORE HAVE
TRIMMED BACK POPS ACROSS MUCH OF THE CWA FOR SATURDAY COMPARED TO
THE GUIDANCE GRIDS WHILE THE LOW LEVELS MOISTEN...WITH MORE
WIDESPREAD POPS FOR SATURDAY NIGHT INTO MONDAY. STILL THINK THESE
COULD BE OVERDONE ON THE NORTHERN/EASTERN EDGES WITH MAJORITY OF
PRECIP MOST LIKELY CONFINED TO THE SOUTHERN AND POSSIBLY CENTRAL
CWA. COLDER AIR CONTINUES TO PUSH INTO THE CWA SO HAVE A COOLING
TREND FOR SATURDAY INTO EARLY NEXT WEEK...WITH MUCH OF H85 TEMPS
JUST BELOW FREEZING BY MONDAY INTO TUESDAY. THIS SHOULD PUSH SFC
TEMPS INTO THE 10 TO 20 DEGREE BELOW NORMAL RANGE BY EARLY NEXT
WEEK. OVERALL TRENDED TEMPS DOWNWARD FOR THE WEEKEND...WITH THE
COOLER AIRMASS IN PLACE AND POSSIBILITY OF PRECIP/CLOUD COVER.

&&

.AVIATION...22/18Z
ISSUED AT 1222 PM CDT TUE APR 22 2014

HIGH PRESSURE DRIFTS ACROSS IOWA EXITING EASTERN IOWA BY 12Z.  A
SURFACE LOW OVER THE HIGH PLAINS WITH A WARM FRONT INTO NW IA WILL
AFFECT LOCATIONS AFT 06Z.  WINDS WILL SWITCH AROUND TO A SRLY
DIRECTION FM KDSM AND KMCW WEST AND BY 12Z ALL TAF LOCATIONS WILL
SEE A SOUTHERLY DIRECTION.  WINDS WILL ALSO INCREASE TO 15 TO 25KTS
THROUGH THE MORNING.  AS WARMER AND MORE UNSTABLE AIR MOVES IN
SHOWERS AND ISOLD THUNDERSTORMS WILL DEVELOP ACROSS TAF LOCATIONS
TOWARDS 18Z.

&&

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

$$

SHORT TERM...REV
LONG TERM...BEERENDS
AVIATION...FAB



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