Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 222132
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
332 PM CST SAT NOV 22 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 316 PM CST SAT NOV 22 2014

PLENTY OF MINOR CHALLENGES FOR TONIGHT`S FORECAST. TEMPERATURES
CONTINUE TO WARM THIS AFTERNOON WITH CLEARING AREA ADVANCING
NORTHEAST AT THE MOMENT WAS SFC BOUNDARY MOVES NORTHEAST. SOUTH
MOISTURE ALOFT HAS BEEN INCREASING SINCE THE MORNING HOURS AND WITH
THE NEXT SURGE OF SFC MOISTURE WILL SEE LOW CLOUDS AND AREAS FOG
AGAIN FILL IN DURING THE EVENING HOURS. LIKELY THAT SATURATION WILL
LEAD TO PATCHY DRIZZLE TURNING OVER TO LIGHT RAIN AFTER 9 TO 10 PM
AS ISENTROPIC LIFT INCREASES WITH MOISTURE TRANSPORT. WILL CONTINUE
TREND TO RAISE POP OVERNIGHT WITH LIGHT RAIN OR DRIZZLE AND FOG. FOR
NOW...WILL NOT RAISE HEADLINES FOR VISIBILITY...THOUGH FAR NORTH MAY
STILL PRESENT SOME ISSUES IN THE MID EVENING HOURS. WOULD LIKE TO IF
WARM AIR ADVECTION OVERCOMES THE INCREASING MOISTURE FIRST...WHICH
WOULD KEEP FOG IN THE 2 TO 5 MILE RANGE AT WORST. WILL PASS ALONG TO
EVENING SHIFT FOR CONSIDERATION. OTHERWISE...WITH SUSTAINED SOUTH
FLOW OVERNIGHT AND AMPLE WARM AIR ADVECTION OVERNIGHT MINS SHOULD
REMAIN QUITE MILD AND HAVE RAISED MINS ACROSS THE AREA. LOOKING FOR
LOWS IN THE UPPER 30S TO LOWER 40S NORTH AND IN THE UPPER 40S OVER
THE FAR SOUTH. IRONICALLY...THIS WILL BE MUCH WARMER THAN THE HIGHS
OF THE PAST 11 DAYS. BUT IT WONT LAST TOO LONG AS THE SYSTEM OVER
THE SOUTH ADVANCES NORTH IN THE NEXT 24 HOURS.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 316 PM CST SAT NOV 22 2014

SUNDAY STARTS OUT WARM WITH A SURFACE LOW LIFTING OUT OF THE
SOUTHERN PLAINS INTO EASTERN IOWA AS AN UPPER TROUGH DIGS INTO
WESTERN IOWA. THIS WILL AID IN CONTINUING TO DRAW WARM MOIST AIR
UP OVER IOWA. I NUDGED BOTH TEMPS AND MAX TEMPS UP AS WELL AS
DEWPOINTS ON SUNDAY. PRECIP OVER THE STATE WILL BE ALL RAIN
DURING MOST OF THE DAY. THERE WILL BE A NARROW WINDOW LATE IN THE
AFTERNOON FOR A MIX AS COLDER AIR BEGINS TO PUSH IN.

SUNDAY NIGHT THE TROUGH CONTINUES TO DEEPEN AND MOVE INTO IOWA.
COLDER AIR WILL PUSH INTO THE STATE. LOOKING AT SOUNDINGS THERE
STILL COULD BE A BRIEF PERIOD ACROSS THE NORTH THROUGH 00Z MON
WHERE SOME MIXED PRECIP OCCURS BUT THE COLDER AIR REALLY COMES
CHARGING INTO THE STATE AND IS VERY DEEP SO SOUNDINGS SHOW THE
ENTIRE COLUMN JUST MOVING BELOW ZERO...NO WARM LAYER ANYWHERE FOR
MELTING TO OCCUR. THE TRANSITION TO SNOW WILL BE QUICK. SNOWFALL
AMOUNTS AT THIS POINT ARE DIFFICULT TO PREDICT...ESPECIALLY
NORTHEAST. THIS IS A RAPIDLY DEEPENING STORM AND THINGS COULD
EVOLVE DIFFERENTLY THAN MODELS ARE SHOWING WHICH WOULD MEAN
BIGGER IMPACTS... ESPECIALLY EAST/NORTHEAST. IF THE STORM
DEVELOPS JUST A LITTLE FURTHER WEST THAN MOST MODELS SHOW THEN
NORTHEAST IOWA COULD POTENTIALLY SEE SOME MODERATE SNOWFALL
AMOUNTS. IF IT DOES IN FACT DEVELOP FURTHER EAST AS MOST MODELS
SUGGEST THEN WE WILL ONLY SEE LIGHT SNOWFALL AMOUNTS.

AT THIS POINT BASED ON A BLEND OF THE MODELS...FOR MOST OF IOWA
IT DOES NOT APPEAR THAT WE WILL SEE MUCH SNOW OUT OF THIS AS LOWER
LAYERS DRY OUT SOME. NOT SURE I BUY THAT WE WILL DRY OUT AT ALL
JUST YET...BUT ACCUMULATIONS ACROSS ALL BUT THE NORTHEAST SHOULD
BE UNDER ANY ADVISORY CRITERIA. THE EXCEPTIONS TO THIS...IF THE
GFS VERIFIES...WOULD BE THE EAST AND NORTHEAST. THE GFS SHOWS MUCH
STRONGER QG FORCING INTO THIS AREA AS THE PRECIP IS SHIFTING EAST
ACROSS THE AREA AND COLDER AIR PLUNGES IN. BOTH THE NAM AND GFS
PRINT OUT A HALF INCH OR MORE OF QPF WHILE THE EURO IS QUITE A BIT
LESS AND EVEN FURTHER EAST. THE NAM IS FURTHER SOUTH WITH THE
HEAVIER QPF WHERE TEMPS WILL HOLD ABOVE FREEZING A BIT LONGER THAN
ACROSS THE NORTHEAST. AT THIS POINT THERE ARE BIG DISCREPANCIES
BETWEEN MODELS WITH THE GFS BEING THE STRONGEST AND THE OUTLIER OF
THE MODELS. THEREFORE I WENT WITH A COMPROMISE OF THE TWO BRINGING
A BIT MORE QPF NORTH THAN THE NAM HAD AND LESS THAN THE GFS HAD. THE
NAM COBB OUTPUT IS SHOWING A FEW TENTHS OF SNOW ACROSS THE NORTHEAST
AT BEST WHILE THE GFS HAS MODERATE SNOWFALL AMOUNTS. AT THIS POINT
WE WILL BEEF UP WORDING IN THE HWO AND WILL CONTINUE TO MONITOR
FOR CHANGES TO HEADLINES BUT THE GFS IS THE ODD MODEL OUT SO MY
CONFIDENCE ISN`T HIGH ENOUGH TO CHANGE THINGS JUST YET. ONE THING
THAT NEEDS TO BE CONSIDERED BEGINNING LATE SUNDAY NIGHT AND
MONDAY IS WIND. I DO NOT SEE A BLOWING SNOW POTENTIAL AT THIS
POINT. MUCH OF THE SNOW WE GOT ACROSS THE NORTH WILL HAS OR WILL
MELT AND ANY SNOW WE GET WON`T BE ENOUGH TO COVER THE GRASS TO A
SUFFICIENT DEPTH. THERE COULD BE SOME ISSUES WITH DRIFTING SNOW
CREATING SLICK ROADS WHICH WILL NEED TO BE CONSIDERED LATER.

BEYOND MONDAY....THE DEEP UPPER LEVEL TROUGH PARKS ITSELF OVER THE
UPPER MIDWEST FOR ANOTHER PROLONGED PERIOD OF COLDER TEMPERATURES.
AN UPPER LEVEL RIDGE DEVELOPS OVER THE WEST WHICH COULD MODERATE
TEMPS OVER THE UPPER MIDWEST AS IT SHIFTS THE TROUGH AXIS EAST BUT
AGAIN THE EURO IS MORE BULLISH ON THIS HIGH WHILE THE GFS IS MORE
MUTED. WE ALSO HAVE TO DEAL WITH A CLIPPER SYSTEM THAT ALL MODELS
ARE PICKING UP ON FOR TUESDAY NIGHT/WEDNESDAY FOLLOWED BY ANOTHER
SHOT OF COLD AIR WITH A POTENTIAL FOR ADDITIONAL LIGHT SNOW
WEDNESDAY NIGHT INTO THANKSGIVING.  LOWS FROM MID WEEK INTO THE
HOLIDAY WEEKEND WILL BE IN THE SINGLE DIGITS AND TEENS WITH HIGHS IN
THE TEENS AND 20S.

&&

.AVIATION...22/18Z
ISSUED AT 1141 AM CST SAT NOV 22 2014

MAIN CONCERNS WILL REMAIN VSBY AND CIGS NEXT 24 HOURS. CONDITIONS
HAVE IMPROVED A BIT...BUT PLENTY OF LOW STRATUS AROUND YET THROUGH
00Z AND EXPECTED THAT IFR/VLIFR CONDITIONS WILL RETURN AFT 00-03Z
MANY AREAS. DRIZZLE AND POTENTIAL FOR -RA INCREASE OVERNIGHT
SOUTHEAST TO NORTHWEST WITH TIME. HAVE ADDED WITH DECREASED CIGS
AND VSBY AS WELL. WINDS REMAIN SOUTH 12 TO 15KTS THROUGH TONIGHT
GRADUALLY SHIFTING NW BY 18Z SUNDAY NORTHWEST HALF./REV


&&

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

$$

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



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