Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 041119
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
619 AM CDT WED MAY 4 2016

.SHORT TERM.../TODAY/
ISSUED AT 329 AM CDT WED MAY 4 2016

LITTLE SENSIBLE WEATHER TODAY AS THE OVERNIGHT SYSTEM DEPARTS TO
THE EAST AND HIGH PRESSURE MOVES IN FROM THE NORTHWEST. THE
STATE WILL BE IN THE THERMAL TROUGH IN THE WAKE OF THE OVERNIGHT
COLD FRONT AND WEAK COLD ADVECTION WILL CONTINUE INTO THIS
MORNING. THE ADVECTION WILL TRANSITION TO MORE NEUTRAL TO WEAK
WARM ADVECTION THIS AFTERNOON. GOOD MIXING CONDITIONS TODAY WITH
MIXING OCCURRING TO ABOVE 800 MB AND WITH THE DRY AIR IN
PLACE...EXPECT SUPER ADIABATIC LAPSE RATES NEAR SFC WHICH WILL
HELP WARM TEMPERATURES INTO THE MID TO UPPER 60S BY MID AFTERNOON.
A FEW CUMULUS CLOUDS MAY DEVELOP OVER THE EAST LATE THIS MORNING
IN THE EARLY AFTERNOON BUT SHOULD DISSIPATE LATER IN THE DAY WITH
THE ARRIVAL OF EVEN DRIER AIR. THE RESULT WILL BE AN ABUNDANCE OF
SUNSHINE TODAY. THE NORTHWEST WINDS WILL BE GUSTY WITH GUSTS OVER
25 MPH AT TIMES.

.LONG TERM.../TONIGHT THROUGH TUESDAY/
ISSUED AT 329 AM CDT WED MAY 4 2016

TEMPERATURES WERE THE MAIN FOCUS OF THE MID-TERM AND THEN POPS
RETURNING TO THE FORECAST OVER THE WEEKEND AND INTO NEXT WEEK AS
THE PATTERN BECOMES A BIT MORE ACTIVE. LEANED SLIGHTLY MORE
TOWARDS THE WARMER GFS TONIGHT THROUGH FRIDAY AND THEN UTILIZED A
BLEND OF THE ECMWF/GFS THROUGH THE REMAINDER OF THE FORECAST
PERIOD.

TONIGHT THROUGH FRIDAY...SURFACE HIGH PRESSURE BUILDS INTO THE
STATE AND PROVIDES ONE LAST COOL (WELL BELOW NORMAL) PERIOD
TONIGHT INTO THURSDAY MORNING. RADIATIONAL COOLING LOOKS TO PUT
MINIMUM TEMPERATURES INTO THE UPPER 30S ACROSS NORTH TO NORTHEAST
PORTIONS OF THE FORECAST AREA WHICH RESULTED IN SLIGHTLY LOWERING
TEMPERATURES FROM PREVIOUS FORECAST. THE SURFACE HIGH MEANDERS
EAST THROUGH THE DAY THURSDAY INTO THURSDAY NIGHT...ENOUGH TO
ALLOW FOR THE WESTERN PORTIONS OF THE FORECAST AREA TO WARM INTO
THE MID-70S WITH SOME WEAK MIXING DEVELOPING. THE RIDGE CONTINUES
TO MOVE EAST THURSDAY NIGHT INTO FRIDAY WHICH BRINGS SOME WEAK
RETURN FLOW PAST 06Z FRIDAY AND THUS KEEPING TEMPERATURES UP
SLIGHTLY OVERNIGHT. RAISED MINIMUM TEMPERATURES SLIGHTLY THURSDAY
NIGHT. NOT CONFIDENT ATTM TO MENTION A NON-DIURNAL TEMPERATURE
TREND AS WINDS MAY NOT BE STRONG ENOUGH OVERNIGHT ACROSS THE
FORECAST AREA...BUT SOMETHING TO CONSIDER IN NEXT PACKAGE.

DEEP MIXING DEVELOPS LATE FRIDAY MORNING AND INTO THE AFTERNOON
HOURS...WITH WINDS REMAINING WEST-SOUTHWEST THROUGHOUT THE DAY.
NUDGED UP WINDS ACROSS THE FORECAST AREA AS MODELS SEEM TO
UNDERCUT THE MIXING DURING THIS TYPE OF SETUP. BUFR SOUNDINGS
SUGGEST WINDS ATOP THE MIXED LAYER RANGE FROM 25-30 KNOTS...AND
THUS CONFIDENT TO INCREASE WINDS. ALSO WITH THE BUFR
SOUNDINGS...VERY DRY DEW POINTS ARE LIKELY DURING THE AFTERNOON
AND LOWERED THEM ROUGHLY 2-4 DEGREES ACROSS THE FORECAST AREA DUE
TO THE GOOD MIXING...AND STILL MAY BE TOO HIGH. REGARDLESS...WITH
THE DRIER AIR MASS AND SLIGHTLY STRONGER MIXING...RAISED MAX
TEMPERATURES A COUPLE OF DEGREES FOR FRIDAY. THIS WAS ROUGHLY 2-3
DEGREES ABOVE THE WARMEST GUIDANCE...WHICH WAS MAINLY THE GFS.

FRIDAY NIGHT THROUGH SUNDAY...NORTHWEST FLOW ALOFT DEVELOPS DURING
THE WEEKEND AND MODELS ARE HAVING A DIFFICULT TIME PINPOINTING
ANY CANADIAN CLIPPER SYSTEM TO AFFECT THE STATE. ECMWF/GFS DO
BRING A WEAK FRONTAL BOUNDARY ACROSS THE REGION LATE FRIDAY NIGHT
INTO SATURDAY AND WILL BE THE FOCUS FOR THUNDERSTORM DEVELOPMENT.
THE LIMITING FACTOR WITH THIS SYSTEM IS MOISTURE AND HAVE LOW
CONFIDENCE WITH ANY WIDESPREAD PRECIPITATION OVER THE WEEKEND. THE
SURFACE HIGH OVER THE GREAT LAKES LOOKS TO BECOME THE DOMINANT
WEATHER FEATURE TOWARDS THE END OF THE WEEKEND AND THUS LEANED
TOWARD A DRIER FORECAST EXCEPT ACROSS THE SOUTHWEST WHERE THE
BOUNDARY REMAINS. PLUS...COULD EVEN TREND DRIER SUNDAY NIGHT INTO
MONDAY IF GFS HOLDS TRUE.

MONDAY INTO TUESDAY...A LARGE CUTOFF LOW FINALLY IS ABLE TO MOVE
EAST EARLY NEXT WEEK AND LOOKS TO AFFECT THE STATE BY MONDAY NIGHT
INTO TUESDAY. THERE ARE STILL PLENTY OF DISCREPANCIES IN THE
EXTENDED PERIOD BUT AT LEAST SOME AGREEMENT WITH THE UPPER LOW
TRACKING ACROSS THE PLAINS DURING THE AFOREMENTIONED TIME.

&&

.AVIATION.../FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING/
ISSUED AT 618 AM CDT WED MAY 4 2016

VFR CONDITIONS ARE FORECAST TO PREVAIL THROUGH THE PERIOD. SCT
CUMULUS MAY DEVELOP AROUND 5 KFT LATE MORNING INTO THE EARLY
AFTERNOON OTHERWISE MOSTLY CLEAR SKIES WILL PREVAIL. BREEZY NORTH
WINDS TODAY WILL DIMINISH BY THIS EVENING.

&&

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

$$

SHORT TERM...DONAVON
LONG TERM...PODRAZIK
AVIATION...DONAVON


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