Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 211148
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
548 AM CST SUN DEC 21 2014

.UPDATE...
ISSUED AT 536 AM CST SUN DEC 21 2014

HAVE TRIMMED OFF MORE OF THE FOG ADVISORY WITH CONTINUED IMPROVEMENT
IN SOUTHEAST MIXING SFC FLOW OF 8-12 MPH. REST OF THE REMAINING
COUNTIES ALONG THE HWY 20 CORRIDOR WILL PROBABLY ALSO BE CANCELED
EARLY AND WILL WATCH FOG TRENDS THROUGH SUNRISE. ADDITIONAL SPOTTY
AREAS OF DRIZZLE MOVING OUT OF CENTRAL IA THIS MORNING BUT SFC
TEMPS CWA WIDE ABOVE 32 EXCEPT RIGHT AT FREEZING ALONG THE HWY 20
CORRIDOR EAST OF DBQ INTO NW IL.

&&

.SYNOPSIS...
ISSUED AT 325 AM CST SUN DEC 21 2014

LATEST SFC ANALYSIS WAS INDICATING SOUTH TO SOUTHEASTERLY RETURN
FLOW GRADIENT IN FULL SWING ACRS THE AREA...ALONG WITH LLVL MOISTURE
TRANSPORT AND WARM AIR ADVECTION. THE LOCAL 88D WAS INDICATING MORE
SWATHS OF DRIZZLE MOVING EAST ACRS THE CWA...BUT ALMOST CWA-WIDE SFC
TEMPS ARE AT OR ABOVE FREEZING LIMITING MUCH OF ANY ADDITIONAL
FREEZING DRIZZLE THREAT EVEN ALONG THE HWY 20 CORRIDOR...MAYBE A BIT
MORE LINGERING POTENTIAL THRU 6 AM AROUND THE FREEPORT AREA IN NW
IL. SFC OBS AND WEB CAMS INDICATING DENSE FOG IMPROVEMENT ACRS AT
LEAST THE SOUTH HALF OF THE ONGOING ADVISORY AND WILL DROP THAT
SECTION WITH 4AM FCST PACKAGE. ALOFT...WATER VAPOR IMAGERY
INDICATING WEAK VORT MOVING EAST TOWARD NORTHERN IL WITH TEMPORARY
UPPER RIDGE BULGE SET TO SLIDE ACRS EASTERN IA AND NORTHWEST IL THIS
MORNING...BUT STRONGER WAVE NOTED UPSTREAM ACRS THE WEST CENTRAL
PLAINS WHICH WILL LOOK TO PROPAGATE EAST ACRS CENTRAL IA BY THIS
AFTERNOON.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 325 AM CST SUN DEC 21 2014

TODAY...WILL KEEP SOME LINGERING FOG MENTION IN THE NORTHERN THIRD
THROUGH LATE MORNING...ALTHOUGH WITH INCREASING SOUTHERLY SFC FLOW
OF 7-12 KTS EXPECT MIXING AND REDUCTION OF THE DENSE FOG...REST OF
THE ADVISORY MAY BE CANCELED EARLY LATER THIS MORNING. ALSO LINGERING
SWATHS OF DRIZZLE TO WALK OUT OF THE CWA/ESPECIALLY THE NORTH HALF/
THROUGH MID TO LATE MORNING BUT AS WAVE ALOFT DEPARTS THE CWA MY BE
MAINLY DRY BY MIDDAY IF NOT EARLIER. CURRENTLY ADVERTISED HIGH TEMPS
LOOK ON TRACK WITH ONGOING WARM AIR ADVECTION OUT OF MO...DESPITE
THE CLOUDS AND HIGHER SFC LAYER RH/DPTS MUCH OF THE CWA MAY REACH
40 DEGREES OR MILDER BY THIS AFTERNOON. UPSTREAM WAVE/VORT COMPLEX
NOTED ABOVE...ROLLING ACRS CENTRAL IA BY THIS AFTERNOON WILL LOOK TO
KICK UP SOME SPOTTY AREAS OF DRIZZLE OR EVEN LIGHT RAIN/IF MOISTURE
LAYER CAN DEEPEN ENOUGH/ ACRS THE WESTERN THIRD OF THE CWA AFTER MID
AFTERNOON. SOME PATCHY FOG STILL POSSIBLE NORTH OF I80 FROM LATE
MORNING AND INTO THE AFTERNOON...BUT EXPECT RATHER BRISK SOUTHERLY
BL FLOW TO MIX OUT ANY DENSE FOG POTENTIAL INTO THE EVENING.

TONIGHT...ONGOING LOW MOIST FLOW AND WAA TO KEEP TEMPS STEADY IN THE
MID TO UPPER 30S IF NOT MILDER IN A FEW SPOTS OVERNIGHT...THUS NO
CHC FOR ANY MIX OR FREEZING PRECIP POTENTIAL TONIGHT. CONTINUING
UPTICK IN APPROACHING FORCING OFF THE DIGGING WAVE JUST TO THE
WEST...ALONG WITH DEEPENING VERTICAL MOISTURE PROFILES/PWATS
EXPECTED TO RISE TO 0.50 TO 0.60+ AFTER MIDNIGHT/...TO FUEL
INCREASING RAIN DEVELOPMENT FROM WEST TO EAST FROM MID EVENING AND
ESPECIALLY INTO THE POST-MIDNIGHT PERIOD. BULK OF MEASURABLE PRECIP
WILL STILL LOOK TO REAMING WEST OF THE MS RVR THROUGH DAWN MONDAY
MORNING. RAINFALL AMOUNTS STILL WILL LOOK TO REMAIN ON THE LIGHT
SIDE TONIGHT WITH MOST AREAS THAT GET MEASURABLE AT 0.05 OR LESS BY
12Z MON.   ..12..

.LONG TERM...(MONDAY THROUGH NEXT SATURDAY)
ISSUED AT 325 AM CST SUN DEC 21 2014

OUR FORECAST FOR THE LONG TERM REMAINS LARGELY CONSISTENT FROM ITS
EARLIER ISSUANCES...BUT OBVIOUS TO ANYONE FOLLOWING THIS PERIOD IS
THAT THE ELEPHANT IN THE ROOM HAS FINALLY LEFT THE HOUSE. NO MODELS
WITHIN THE 00Z SUITE OF DATA HAVE RETAINED THE NEGATIVELY TILTED
INTENSE LOW PRESSURE WITH HEAVY DEFORMATION ZONE SNOWS/WINTER STORM
FOR THE UPPER MIDWEST. IT IS GONE...AS THE PHASING OF NORTHERN AND
SOUTHERN STREAM ENERGY ON TUESDAY APPEARS MORE DELAYED AND LESS
LIKELY TO OCCUR OVER THE MIDWEST. THIS RESULTS IN A MORE EASTERLY
PATH TO THE SECONDARY LOW AND FAR LESS OF A NOTABLE EVENT ANYWHERE.

GETTING BACK TO MONDAY INTO TUESDAY...THE SIGNAL FOR A PERIOD OF
LIGHT TO MODERATE RAIN CONTINUES TO BE OFFERED IN THIS PERIOD ON
NEARLY EVERY MODELS AS THE INITIAL STRONG NORTHERN WAVE DROPS INTO
WESTERN IOWA...ALLOWING FOR A SLOW MOVING LOW PRESSURE TO MOVE EAST
AND OCCLUDE OVER THE UPPER MISSISSIPPI VALLEY. A COLD RAIN IS IN THE
OFFING AS TEMPERATURES AT 850 AND BELOW ARE BOTH ABOVE FREEZING AND
SATURATED...THUS SNOW SHOULD NOT SURVIVE THAT LAYER UNTIL WE ARE
WELL ON THE BACKSIDE AND COOL THE ENTIRE COLUMN...AND WITH NO
SIGNIFICANT CLOSED LOW JUST TO THE EAST AS SOME HAD INDICATED
EARLIER...THERE SHOULD BE LITTLE MOISTURE LEFT TO PRECIPITATE OUT OF
THE ATMOSPHERE. THUS...ONLY VERY LIGHT SNOW SHOWERS SEEM LIKELY FROM
TUESDAY EVENING THROUGH WEDNESDAY. THERE REMAINS SOME DIFFERENCES ON
TIMING OF THE BEST FORCING...WHICH THE GFS HAS FASTER THAN THE
ECMWF. THE GFS HAS STRONG WAA FORCING BY MORNING WEDNESDAY...LASTING
THROUGH VERY EARLY EVENING BEFORE DRY SLOTTING OUR CWA...LIKELY WITH
DRIZZLE AND FOG TO FOLLOW. THE EC IS SLOWER...AND HAS A SIMILAR
ROUND OF FORCING MONDAY LATE AFTERNOON THROUGH MONDAY NIGHT.  SINCE
LIGHT MEASURABLE RAIN IS LIKELY BOTH MONDAY AND MONDAY NIGHT IN EACH
SCENARIO...I HAVE ELECTED TO HAVE A PROLONGED PERIOD OF LIKELY
POPS...WITH CATEGORICAL CENTERED MAINLY MONDAY AFTERNOON AND
EVENING. IT WILL DEFINITELY BE A WET PERIOD BUT WINDS SOUTH WINDS
BLOWING AT 10 TO 15 MPH...NO HAZARDS ARE EXPECTED. THE SYSTEM TO THE
EAST SHOULD NOT CREATE A WIDESPREAD GRADIENT WIND EVENT IN THE
MIDWEST. THUS FOR OUR CWA...WINDS ALSO DO APPEAR LIGHTER THAN
EARLIER FORECAST BY OUR OFFICE...AND THAT IS THE BIGGEST CHANGE TO
THE OFFICIAL GRIDS. WINDS SEEM UNLIKELY TO EXCEED 30 MPH ON
GUSTS...SO WHILE BREEZY...WEDNESDAY DOES NOT LOOK TO BE ANYWHERE
CLOSE TO ADVISORY LEVELS.

THURSDAY THROUGH SATURDAY...MODELS CONTINUE TO SHOW A SECONDARY LOW
MOVING THROUGH THE MIDWEST...BUT HAVE STARVED THIS LOW OF BOTH
SIGNIFICANT DYNAMICS AND MOISTURE. THIS MAY BRING SOME LIGHT SNOW TO
THE REGION...BUT IN GENERAL...CHRISTMAS AND FRIDAY REPRESENT TWO
MORE MODERATE DAYS BEFORE COLDER WEATHER RETURNS FOR THE WEEKEND.

ERVIN

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 536 AM CST SUN DEC 21 2014

JUST SPOTTY REGULAR DRIZZLE MOVING ACRS THE TAF SITES THIS MORNING
WITH SFC TEMPS ABOVE FREEZING. FOG IMPROVING AS WELL WITH MAINLY
MVFR VSBYS AROUND NOW...AND A TEMPORARY RISE TO LOW VFR CIGS ALONG
AND SOUTH OF I80. DO EXPECT CIGS TO TREND DOWN AGAIN TO LOWER MVFR
OR EVEN POSSIBLY IFR LATER THIS MORNING AND INTO THE AFTERNOON
WITH ADDITIONAL LLVL MOISTURE INFLUX OUT OF MO. SOUTH TO SOUTHEAST SFC
WINDS OF 10-15 KTS INTO THE EVENING. TONIGHT...MANY CIGS TO LOWER
TO IFR AGAIN...AND POSSIBLY SOME 2-4SM FOG BUT SFC WINDS MAINTAINING 8-13KTS
SHOULD LIMIT WIDESPREAD DENSE OR MUCH OF ANY DENSE FOG TONIGHT.
MORE DRIZZLE AND LIGHT RAIN TO INCREASE FROM THE WEST ESPECIALLY
AFTER MIDNIGHT IN THE VCNTY OF CID AND DBQ.    ..12..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR BUCHANAN-
     DELAWARE.

IL...NONE.
MO...NONE.
&&

$$

UPDATE...12
SYNOPSIS...12
SHORT TERM...12
LONG TERM...ERVIN
AVIATION...12






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