National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KDMX 052330
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
530 PM CST THU MAR 5 2015

...UPDATED AVIATION DISCUSSION...

.SHORT TERM /TONIGHT/...
ISSUED AT 305 PM CST THU MAR 5 2015

HIGH PRESSURE CURRENTLY CENTERED OVER SE IOWA WILL CONTINUE TO SLIDE
SOUTHEAST AWAY FROM THE STATE TONIGHT. RETURN FLOW SETS UP WITH WAA
ALOFT TONIGHT ACROSS IOWA. AN WEAK UPPER LEVEL SHORTWAVE WILL DIVE
SOUTHEASTWARD ACROSS THE STATE TONIGHT...RESULTING IN MAINLY SOME
MID LEVEL CLOUD COVER AND INCREASING WINDS AS THE SFC PRES GRADIENT
TIGHTENS. THEREFORE WITH THE WAA...INCREASING WINDS AND CLOUD COVER
TEMPS NOT EXPECTED TO FALL OFF MUCH OVERNIGHT. AS WINDS BECOME MORE
SOUTHERLY TOWARD MORNING...STEADY TO WARMING TEMPS EXPECTED TOWARD
SUNRISE. LOWS SHOULD BOTTOM OUT MAINLY THIS EVENING WITH SINGLE
DIGITS ABOVE ZERO EXPECTED ACROSS THE NORTHEAST...AND TEENS ACROSS
THE REMAINDER OF THE CWA.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 305 PM CST THU MAR 5 2015

BIGGEST STORY THROUGH THE NEXT SEVEN DAYS IS CERTAINLY THE WARMING
TREND DURING THE PERIOD. A MAJOR FACTOR DURING THIS PERIOD IS THE
LACK OF SNOW COVER THROUGH NEBRASKA...KANSAS AND MISSOURI AND INTO
SW IOWA. THIS WILL ALLOW GOOD WARMING INTO IOWA WITH NO
MODIFICATION TO THE SOUTH BEFORE THE AIR ARRIVES. GOOD WARM
ADVECTION AT 925 MB TONIGHT WILL HAVE THE 925 MB TEMPERATURES 20C
WARMER THAN THIS MORNING. THIS ALONG WITH THE SWITCH TO SOUTHERLY
WILL HELP TEMPERATURES RISE INTO THE MID 30S TO MID 40S BOTH
FRIDAY AND SATURDAY. MUCH OF THE SNOW ACROSS THE WESTERN HALF OF
IOWA SHOULD MELT ON BY SATURDAY.

SHORT WAVE ENERGY WILL DROP SOUTHEAST SATURDAY NIGHT INTO EARLY
SUNDAY. THE BULK OF THE KINEMATIC FORCING ASSOCIATED WITH THE
SYSTEM IS EXPECTED TO BE TO THE NORTHEAST OF THE AREA HOWEVER BOTH
THE ECMWF AND GEM HAVE A SECOND STRONGER WAVE FOLLOWING THAT WOULD
BRING MORE FORCING INTO NORTHERN IOWA. HAVE INCREASED POPS FOR
SNOW A BIT OVER THE NORTH AND HOPEFULLY WILL BE ABLE TO LATCH ON
TO THE SECOND IMPULSE WITH FUTURE FORECASTS. SUNDAY WILL BE A
BIT WARMER THOUGH A BOUNDARY WILL MOVE THROUGH FOLLOWING THE UPPER
SYSTEM PASSAGE AND BRING A SWITCH TO NORTHWEST WINDS. MAY HAVE
SOME FOG DEVELOP EACH NIGHT WHERE GOOD SNOW MELT OCCURS ESPECIALLY
SATURDAY NIGHT AS HIGH PRESSURE MOVES ACROSS THE STATE AND WINDS
DIMINISH.

THE BIGGEST CHANGE IN THE PATTERN ARRIVES TUESDAY INTO WEDNESDAY
AS THE UPPER FLOW TRANSITIONS FROM WEAK NORTHWEST TO ZONAL TO
POSSIBLY RIDGING. SFC FLOW WILL BECOME SOUTHWESTERLY WHICH IS WILL
PROMOTE GOOD WARMING POTENTIAL. HIGHS TUESDAY WILL BE IN THE 50S
AND 60S THOUGH IT IS POSSIBLE THAT SOME RESIDUAL SNOW PACK OVER
THE FAR NORTHEAST LIMITS READINGS A BIT. WEDNESDAY HAS THE
POTENTIAL TO BE SPECTACULAR AS THE THERMAL RIDGE PASSES THROUGH
THE STATE. POTENTIAL IS THERE TO REACH 70 IN SOUTHWEST TO NEAR DES
MOINES PENDING A GOOD AMOUNT OF SUN. THURSDAY WILL BE COOLER BUT
STILL MILD CONSIDERING THE RECENT COLD WEATHER.

&&

.AVIATION...06/00Z
ISSUED AT 530 PM CST THU MAR 5 2015

VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. WEAK SHORTWAVE
MOVES ACROSS THE STATE OVERNIGHT TONIGHT AND BRINGS A WIND SHIFT
AND INCREASE TOWARDS FRIDAY MORNING. NAM IS VERY BULLISH WITH LOW
STRATUS DEVELOPING FRIDAY MORNING BUT THE SHORTWAVE LACKS ANY
SIGNIFICANT MOISTURE AND SHOULD QUICKLY MOVE EAST WITH THE WEST
TO SOUTHWEST FLOW DEVELOPING FRIDAY.

&&

.HYDROLOGY...
ISSUED AT 305 PM CST THU MAR 5 2015

THE SECOND /AND FINAL/ SPRING FLOOD OUTLOOK OF THE SEASON WAS
RELEASED EARLIER TODAY...AND CALLS FOR A NEAR NORMAL RISK OF
FLOODING THROUGH EARLY JUNE. THAT OUTLOOK DOES NOT GIVE FULL
CONSIDERATION TO ICE JAMS...HOWEVER...AS ICE JAMS TEND TO BE HIGHLY
LOCALIZED EVENTS. THERE HAS BEEN INTEREST IN ICE JAM POTENTIAL NEXT
WEEK GIVEN THE FORECAST WARMUP.

ALTHOUGH THE ICE IS THICK ON AREA RIVERS...AND IS THUS PRIMED FOR AN
ICE JAM EVENT...TYPICALLY A FORCING ELEMENT SUCH AS MODERATE TO
HEAVY RAINFALL AND/OR SIGNIFICANT SNOWMELT IS NEEDED TO START THE
ICE JAM PROCESS. ABSENT EITHER OF THOSE...THEN THERMAL BREAK-UP OF
THE ICE IS THE MOST LIKELY ROUTE WHICH DOES NOT NORMALLY CAUSE
SIGNIFICANT FLOODING ISSUES. THE GOING FORECAST IS NOT SHOWING HIGH
CONFIDENCE OF HEAVY RAINFALL LAST WEEK...AND THE EXISTING SNOWPACK
IS NOT SIGNIFICANT ENOUGH TO YIELD SIGNIFICANT SNOWMELT. THUS...THE
ICE JAM THREAT IS RATHER MINIMAL. ALTHOUGH SOME LOCALIZED MINOR
ISSUES MAY OCCUR...SIGNIFICANT FLOODING IS NOT EXPECTED. HAVING SAID
THAT...SINCE MARCH IS OUR CLIMATOLOGICAL PEAK FOR ICE JAMMING...WE
WILL CONTINUE MONITORING.

AS AN ASIDE...IF THERE WAS A SIGNIFICANT SNOWPACK...THEN FOR ICE
JAMS DRIVEN PRIMARILY BY SNOWMELT...3 TO 5 CONSECUTIVE DAYS WITH
DAILY MAX TEMPERATURES AT LEAST IN THE 40S WOULD BE NEEDED TO START
THE ICE JAM PROCESS. OVERNIGHT LOWS WOULD NOT MATTER MUCH.
ALSO...BASED ON PAST EXPERIENCE...WHENEVER THE DAILY AVERAGE
TEMPERATURE IS 42F OR HIGHER...THEN ICE JAMS ALMOST ALWAYS OCCURRED
WITHIN 1 TO 2 DAYS. FOR ICE JAMS DRIVEN BY THE COMBINATION OF
SNOWMELT AND RUNOFF...3 TO 5 CONSECUTIVE DAYS WITH DAILY MAX
TEMPERATURES AT LEAST IN THE MIDDLE 30S WOULD BE NEEDED TO START THE
ICE JAM PROCESS.

&&

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

&&

$$

SHORT TERM...BEERENDS
LONG TERM...DONAVON
AVIATION...PODRAZIK
HYDROLOGY...ZOGG