Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 271137
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
537 AM CST TUE JAN 27 2015

.SHORT TERM /TODAY/...
ISSUED AT 355 AM CST TUE JAN 27 2015

MAIN CONCERNS TODAY WILL BE TEMPS AND CLOUD COVER THROUGH THE
MORNING HOURS...AND PERHAPS A PORTION OF THE AFTERNOON EAST. TO
VARYING DEGREES...MODELS ALL HINT AT SOME CLOUDS MOVING SOUTHEAST
ALONG THE EASTERN EDGE OF THE H700 RIDGE CAUGHT IN THE NORTHWEST
FLOW EARLY TODAY. HOWEVER...NONE OF THE MODELS IS DOING VERY WELL.
THE HRRR AND NMM WRF MAY HAVE A SLIGHTLY BETTER HANDLE ON THE
SITUATION. EXAMINING THE UPPER LEVEL H700 RIDGE THROUGH THE DAY
TODAY SHOWS THAT IT IS LIKELY TO CONTINUE BUILDING EAST THROUGH THE
AFTERNOON HOURS...ENDING ANY CYCLONIC PORTION OF CIRCULATION WHICH
IS ASSOCIATED WITH THE LEFTOVER SYSTEM FROM YESTERDAY. AT 00Z TUE
THE H850 ANALYSIS SHOWED A PRONOUNCED WAVE TRACKING THROUGH EASTERN
IOWA BACK NORTH TOWARD MINNEAPOLIS...BUT NORTHWEST OF THERE THE FLOW
BECOMES MORE ANTICYCLONIC OVER THE EASTERN DAKOTAS. ANOTHER UPSTREAM
TROUGH IS ALREADY DEVELOPING WITH AN ATTENDANT WARM FRONT OVER THE
WESTERN DAKOTAS. SOME CLOUDS OVER SASKATCHEWAN AND MANITOBA MAY
TRACK SOUTHEAST TOWARD THE REGION THIS AFTERNOON BUT LIKELY ONLY
AFFECT THE FAR EASTERN COUNTIES WITH MID TO HIGH LEVEL CLOUDS. BASED
ON CLOUDS AND LATER TRAJECTORIES...COOLER HIGHS WILL BE HAD OVER THE
NORTHEAST HALF OF THE FORECAST AREA WHILE THE SOUTHWEST HALF WILL
REMAIN MILD FOR JANUARY...BUT NOT AS WARM AS YESTERDAY. WITH A
RATHER WEAK RIDGE AXIS PASSING OVER THE AREA TODAY WINDS WILL REMAIN
LIGHT. HIGHS WILL RANGE FROM THE UPPER 30S NORTHEAST TO THE UPPER
40S SOUTHWEST.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 355 AM CST TUE JAN 27 2015

AM EXPECTING MAX TEMPS FOR WED TO BE VERY SIMILAR TO MONDAY`S HIGHS.
A WARM FRONT WILL CUT ACROSS THE MIDDLE OF THE CWA...LEADING TO A
NOTABLE TEMP GRADIENT...FROM NW TO SE. LOW 40S EXPECTED IN NE CWA
AND UPPER 50S IN SW CWA. NAM MORE AGGRESSIVE WITH LOW LEVEL CLOUD
COVER AND THUS IS A COOL OUTLIER. NAM ALSO STILL THINKS THERE IS
SNOW ACROSS THE CWA SO AM DISCARDING NAM SOLUTION.

A VERY FAST MOVING SHORTWAVE TO IMPACT CWA THURSDAY MORNING. THROUGH
WATER VAPOR IMAGERY...THIS SHORTWAVE CAN BE EASILY PICKED UP COMING
ONTO THE CALIFORNIA COAST AT 06Z TUE. MODELS INITIALIZING WELL WITH
PLACEMENT OF THIS LOW AS IT COMES ONSHORE.

ADDITIONALLY...MODELS CONVERGING ON SOLUTION OF PUTTING THE WAVE
DIRECTLY OVER CENTRAL IOWA AT 06Z THU. THERE IS A SIZABLE DRY AIR
POCKET FROM AROUND 850MB TO 500MB WHICH WILL PREVENT CLOUD
THICKNESS FROM EXCEEDING 5 KFT AND...SUBSEQUENTLY...KEEP THIS
SYSTEM FROM PRODUCING ANYTHING BEYOND LIGHT PRECIP. HAVE BUMPED
UP TEMPS FROM PVS SHIFT. KMCW TO KEST GFS SOUNDINGS SUPPORT MAINLY
DZ/-RA...WITH A VERY NARROW WINDOW OF -IP TO -SN POSSIBLE FROM
AROUND 09Z TO 12Z. PROFILE DURING THIS TIME IS BELOW ZERO UNTIL
NEAR SFC...WHICH IS NOT ENOUGH WARM LAYER DEPTH TO FULLY MELT ALL
SNOW FLAKES. BY 12Z THU...THIS LOW WILL BE OVER NORTHERN ILLINOIS
AND STRONG CAA PLUS SUBSIDENCE WILL BE ADVECTED INTO OUR CWA.
THOUGH SUNSHINE EXPECTED...DAYTIME TEMPS TO ONLY WARM AROUND 3 TO
5 DEGREES FROM OVERNIGHT MINS DUE TO CAA.

THURSDAY`S WINDS ALSO WORTH MENTIONING. MODELS SHOWING 25 KT TO 30
KT WINDS RIGHT OFF THE DECK...APPROACHING 35 KT TO 40 KT TO THE TOP
OF THE MIXED LAYER. SFC PRESSURE GRADIENT OF 3MB/100KM TO SUPPORT
STRONG WINDS AT THE SFC. IN ALL...MAY APPROACH WIND ADVISORY
CRITERIA STARTING EARLY THU AM AND HEADLINE MAY BE WARRANTED IF THIS
SOLUTION HOLDS. A STRONG SFC HIGH WILL MOVE THROUGH THE MIDWEST
FRIDAY...KEEPING FRIDAY QUIET AND HELPING TO DECOUPLE WINDS HEADING
INTO SATURDAY.

FOR THIS WEEKEND...THE 00Z RUNS ARE HOLDING AS THEY ARE SHOWING AN
ALBERTA CLIPPER TYPE SYSTEM LOOKS TO PASS THROUGH THE GREAT LAKES
REGION. THERE WILL BE AN ATTENDANT COLD FRONT TO THIS LOW WHICH IS
BEING PROGGED TO PROPAGATE THROUGH THE CWA SUNDAY MORNING. THE
TIMING HAS CHANGED SOME FROM THE 12Z MON MODEL RUNS TO THE 00Z TUE
RUNS...WITH THE EURO AND GFS DROPPING BACK FROPA UNTIL AROUND 06Z
TO 12Z SUN. MODELS SATURATE THE SKIES FROM TOP DOWN IN ADVANCE OF
THIS SYSTEM...STARTING SATURDAY MORNING. PUSHING TIMING BACK SEEMS
REASONABLE...AS LOW LEVELS NOT SATURATED UNTIL AFTER 00Z SUN. THUS
HAVE PUSHED BACK POPS SLIGHTLY. SOUNDING PROFILE COMPLETELY
SATURATED AND WELL BELOW FREEZING SUNDAY MORNING. HAVE BEGUN TO
NUDGE SUNDAY MORNING POPS UPWARD...WITH FURTHER INCREASES
CERTAINLY POSSIBLE IF THE MODEL SOLNS CONTINUE TO HOLD.

THE PAST FEW MODEL RUNS HAVE CERTAINLY BEEN TRENDING DOWNWARD WITH
TEMPERATURES BEHIND THIS FRONT. ENSEMBLES HAVE 850 MB TEMPS DOWN TO
THE -12C TO -15C RANGE ACROSS THE CWA. SINGLE DIGIT TEMPERATURES
APPEAR VERY POSSIBLE MONDAY AND TUESDAY MORNING.

&&

.AVIATION...27/12Z
ISSUED AT 537 AM CST TUE JAN 27 2015

MAIN CONCERNS THROUGH THE PERIOD ARE LOW CLOUDS. CLOUDS TRAPPED
WITHIN A WEAK UPPER LEVEL RIDGE CONTINUE TO DRIFT SLOWLY SOUTHWEST
INTO THE NORTHEAST AND NORTHERN PORTIONS OF THE FORECAST AREA AT
1130Z. MEANWHILE THE UPPER LEVEL H700 RIDGE IS EXPECTED TO SLOWLY
DRIFT EAST...FORCING THE DECK OF IFR/MVFR CONDITIONS TO SLIDE EAST
AS WELL. THE RAP AND 06Z GFS SUGGEST THE DECK WILL HOLD ON LONGER
...ESPECIALLY NORTHEAST AT KMCW AND KALO. HAVE LENGTHENED CLOUD
RESIDENCE TIME THROUGH 18Z WITH GRADUAL SCT CONDITIONS RETURNING
AFT 18Z THERE. AT THIS TIME...WILL CONTINUE VFR CONDITIONS AT KDSM
AND KOTM WITH BRIEF PERIOD OF MVFR CIGS AT KFOD BETWEEN 15 AND
17Z. REMAINDER OF PERIOD STRONGER SOUTHEAST FLOW RETURNS WITH 12KT
SUSTAINED AND GUSTS AFT 07Z WEST AND NORTH SITES. /REV

&&

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

$$

SHORT TERM...REV
LONG TERM...KOTENBERG
AVIATION...REV


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