Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 171718
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1218 PM CDT FRI OCT 17 2014

.SHORT TERM /TODAY/...
ISSUED AT 316 AM CDT FRI OCT 17 2014

STRONG UPPER LOW PRESSURE SYSTEM CENTERED OVER NW WISCONSIN WILL
CONTINUE TO PUSH TO THE SOUTHEAST TODAY AND DROP A COUPLE OF
SHORTWAVES ACROSS IOWA.  AS THE LOW MOVES TO THE SOUTHEAST THE
PRESSURE GRADIENT WILL TIGHTEN ACROSS IOWA AND THIS WILL BE
RESPONSIBLE FOR STRONG AND GUSTY WINDS TODAY.  STRATUS HAS WORKED
ITS WAY DOWN FROM THE DAKOTAS INTO NW IOWA BY 3 AM AND WILL CONTINUE
TO SHIFT SOUTHEAST ACROSS THE STATE.  BY DAYBREAK OR SHORTLY
THEREAFTER THE ENTIRE FORECAST AREA SHOULD BE ENVELOPED IN THE
STRATUS.  THIS WILL HAMPER TEMPS BUT IT WILL ALSO HAMPER BETTER
MIXING AND SHOULD KEEP WINDS BELOW ADVISORY CRITERIA FOR THE MOST
PART.  FAVORED AREAS WILL COME CLOSE TO ADVISORY CRITERIA BUT IT
SHOULD NOT BE WIDESPREAD ENOUGH TO WARRANT AN ADVISORY...AT LEAST AT
THIS POINT.  IT WILL HOWEVER BE WINDY WITH SOME STRONG GUSTS.

THE MODELS BRING A COUPLE OF SHORTWAVES THROUGH CENTRAL IOWA
TODAY...EACH OF WHICH WILL BRING IN COLDER AND COLDER AIR.  HOWEVER
THE COLDEST AIR IS STILL NOT EXPECTED UNTIL LATER TONIGHT.  CLOUD
COVER WILL HAMPER TEMPS AND I BELIEVE GUIDANCE IS TOO WARM TODAY
GIVEN THE EXTENT OF THE STRATUS COMING DOWN.  SOUNDINGS SHOW A
PRETTY STEEP INVERSION THAT STAYS WITH US THROUGH TODAY THUS I DO
NOT BELIEVE THE STRATUS WILL BREAK UP OR MOVE OUT VERY QUICKLY.  IT
MAY SHIFT TO THE EAST...OUT OF FAR SOUTHWEST IOWA...AS THE LOW
PRESSURE SYSTEM SHIFTS TO THE SOUTHEAST BUT WILL STILL HAVE ENOUGH
OF AN IMPACT TO KEEP TEMPS AT LEAST A COUPLE DEGREES COLDER THAN
WHAT MODEL GUIDANCE IS SUGGESTING.  PRECIP CHANCES ARE VERY LOW
THOUGH A BRIEF SPRINKLE CANNOT BE RULED OUT.  WHILE LOW LEVEL
MOISTURE IS DECENT...SOUNDINGS SHOW RATHER DRY AIR IN THE MID
LEVELS.  TODAY WILL FEEL LIKE FALL WITH CLOUDY SKIES...COOL TEMPS
AND GUSTY WINDS.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 316 AM CDT FRI OCT 17 2014

CYCLONIC FLOW WILL PERSIST OVERNIGHT WITH SMALL PERTURBATION
DROPPING ALONG MISSISSIPPI RIVER VALLEY. LOW CLOUDS EXPECTED TO
PERSIST MUCH OF THE NIGHT IN THIS FLOW ALONG WITH AN INCREASING
FAVORABLE CLIMATOLOGY OF CLOUDS LINGERING LONGER THAN MODELS
INDICATE. GIVEN THE ADDITIONAL CLOUDS TONIGHT HAMPERING DECOUPLING
AND KEEPING WINDS SLIGHTLY HIGHER...LOWS LIKELY TO BE SLIGHTLY
WARMER THAN PREVIOUSLY EXPECTED. SURFACE RIDGING SLIDES THROUGH ON
SATURDAY PRIOR TO THE NEXT SYSTEM DROPPING INTO THE BACKSIDE OF
LARGE EASTERN TROF. SOUTHWEST WINDS WILL INCREASE SATURDAY NIGHT
INTO SUNDAY WITH THERMAL RIDGE BUILDING TOWARD THE STATE.
HOWEVER...MID AND HIGH CLOUDS SHOULD OVERSPREAD IOWA WHICH WILL
LIMIT INSOLATION AND KEEPING READINGS A BIT LOWER THAN OTHERWISE
WOULD BE EXPECTED. BULK OF LIFT AND SATURATION REMAIN WELL NORTH
AND EAST OF IOWA WITH DRY FROPA.

THEREAFTER...BOTH GFS AND EURO INDICATE LARGE UPPER LOW FORMING
ALONG THE EAST COAST WITH JET MIGRATING NORTHWARD INTO SOUTHERN
CANADA BY MIDWEEK. WARMER AIR WILL GRADUALLY EXPAND NORTHWARD INTO
THE MIDWEST WITH SLOWLY MODERATING TEMPERATURES INTO THE LATER
HALF OF NEXT WEEK. MOISTURE AXIS APPROACHES THE STATE BY LATE
WEDNESDAY INTO THURSDAY...HOWEVER FORCING IS NEGLIGIBLE AS
SHORTWAVE LIFTS NORTHEAST INTO CANADA WHERE THE WESTERLIES
RESIDE. THEREFORE...THREAT OF PRECIPITATION WILL BE MINIMAL.

&&

.AVIATION...17/18Z
ISSUED AT 1219 PM CDT FRI OCT 17 2014

CIGS CONTINUE TO HOVER IN THE MVFR/LOW VFR RANGE AND EXPECT THIS
TREND TO CONTINUE THROUGH THE FORECAST PERIOD. MODELS SHOW SOME
THINNING OF THE CLOUD DECK ACROSS THE SOUTHERN SITES LATER TODAY
INTO TONIGHT...BUT EXPECT AS ANOTHER PUSH OF COLD AIR COMES DOWN
TONIGHT...THE CIGS WILL BE REINFORCED AND MAY EVEN LOWER INTO THE
LOWER MVFR RANGE TOWARD SATURDAY MORNING. NORTHWEST WINDS TO
REMAIN GUSTY THIS AFTERNOON AND WILL BEGIN TO DIMINISH AND LOSE
SOME OF THE GUSTINESS TOWARD EVENING. WINDS WILL SHIFT MORE TO THE
NORTH INTO SATURDAY.

&&

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

&&

$$

SHORT TERM...FAB
LONG TERM...COGIL
AVIATION...BEERENDS


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