Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 240928
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
328 AM CST SAT JAN 24 2015

.SYNOPSIS...
ISSUED AT 327 AM CST SAT JAN 24 2015

LATEST SFC ANALYSIS WAS INDICATING PASSING TROF ACRS THE EASTERN CWA
AND INTO WI. STRATOCU DECK ACRS WI AND FAR EASTERN MN...ROTATING
AROUND AND CLIPPING THE NORTHEASTERN CWA ATTM...WITH SOME ADDITIONAL
AREAS POSSIBLY MOVING DOWN ACRS THE EASTERN CWA THIS MORNING OUT OF
EASTERN MN. ALOFT...WATER VAPOR IMAGERY WAS INDICATING THE MAIN
UPSTREAM VORT COMPLEX THAT WILL BE TONIGHTS/SUNDAYS CLIPPER...
ROLLING EASTWARD ACRS B.C. WESTERN CANADA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 327 AM CST SAT JAN 24 2015

TODAY...AFTER THE MORNING STRATOCU IN THE NORTHEASTERN HALF TO
THIRD OF THE CWA MOVES OUT THIS MORNING...JUST SOME OCCASIONAL
HIGHER CLOUDS MOVING ACRS THE REGION ALLOWING SOME SUNSHINE. LOW
TO MID LEVEL NORTHWESTERLIES ACTUALLY WARM AIR ADVECT TODAY AN
AIRMASS FROM THE CENTRAL AND NORTHERN PLAINS...WITH THERMAL
PROFILES WITH EVEN MODERATE MIXING SUPPORTING HIGHS IN THE LOW TO
MID 40S AWAY FROM THE LINGERING SNOW COVER AREAS OF FAR EASTERN/
NORTHEASTERN IA INTO NW IL. UPPER 40S OR EVEN A 50 POSSIBLE IN THE
FAR SOUTH AND SOUTHWESTERN CWA...MAKING FOR THE MILDEST DAY OF THE
PERIOD.

TONIGHT...ASSESSING THE 00Z MODEL RUNS AND SOME OF THE INCOMING NEW
06Z DATA...THE INCOMING CLIPPER TRENDS OF DEEPENING AND DIGGING
FURTHER WEST AND SOUTH ARE STILL THERE FOR THE MOST PART.  THE GFS
AND ECMWF DEEPENING THE SFC LOW TO AROUND 1000 MB WITH THE LOW
DROPPING ACRS THE SOUTHERN CWA BORDER BY 12Z SUNDAY...06Z NAM NOT
QUITE AS DEEP AND FURTHER NORTH NEAR THE QUAD CITIES AT THAT TIME.
THE LATEST SREF BLEND A NICE COMPROMISE FOR NOW AND WILL FOLLOW
THROUGH 12Z SUNDAY. SOME INCOMING LEAD WAA TYPE PRECIP BANDS
STREAKING INTO THE WESTERN CWA AFTER 03Z THIS EVENING...WITH THE
BULK OF THIS PRECIP MAINLY RAIN AND SFC TEMPS HOLDING UP IN THE
MID TO UPPER 30S ALMOST THROUGH MIDNIGHT IN THESE AREAS...NO
FREEZING RAIN THREAT. TOP-DOWN COOLING MAY ALLOW SOME RAIN-SNOW
MIX IN THE FAR NORTHWESTERN CWA TOWARD MIDNIGHT. THEN THE
DEVELOPING DEF ZONE SWEEPS DOWN AND ENGULFS THE NORTHERN HALF OR
EVEN MORE OF THE DVN CWA THROUGH 12Z SUNDAY...AGAIN TAKING INTO
ACCOUNT FORCING SWATHS OF THE LATEST SREF/ECMWF/GFS. THERMAL
PROFILES MAINTAIN MAINLY RAIN ALONG AND SOUTH OF I80...RAIN GOING TO
A RAIN-SNOW MIX FROM I80 UP TO THE HWY 30 CORRIDOR...AND MAINLY A
WET SNOW NORTH OF HWY 30. THE DAY SHIFT WILL HAVE TO MAKE ONE MORE
ANALYSIS OF THE 12Z MODEL RUNS WHEN THEY COME LATER THIS MORNING
WITH AN EVEN BETTER SAMPLED LOW PRESSURE SYSTEM IN THE NORTHWEST FOR
HOPEFULLY MORE MODEL COMPROMISE AND DEFINITION IN LOW PATH
PROPAGATION...ASSOCIATED FORCING SWATH AND OF COURSE THE THERMAL
PROFILES FOR PRECIP TYPE/AMOUNTS. MOISTURE INGEST INTO THE SYSTEM
STILL SEEMS AN UNCERTAINTY...AND THE NEW 00Z ECMWF COMING IN DRIER
WITH JUST A HALF INCH OF SNOW IN THE NORTHWESTERN THIRD OF THE CWA
BY 12Z SUNDAY...MAKE FOR LESS CONFIDENCE IN HIGHER AMOUNTS. FORCING
OFF THE NAM AND IT/S WETTER PROFILES WOULD SUPPORT 1-2 INCHES
ALREADY BY 12Z WEST OF THE MS RVR AND NORTH OF I80. THE GFS SIMILAR
AMOUNTS BUT FURTHER NORTH IN COOLING NORTH-NORTHEASTERLY LLVL FETCH
NORTH OF CEDAR RAPIDS OVER TO EAST OF THE MT CARROLL AREA IN NW IL.
FOR NOW WILL ADVERTISE A WET SNOW ACCUMULATION THRU 12Z SUNDAY OF
AROUND AN INCH OR LITTLE MORE ALONG AND NORTH OF HWY 30...HALF INCH
TO NEAR AN INCH FROM HWY 30S TO I80...AND JUST A FEW TENTHS ALONG
THE I80 CORRIDOR WHERE RAIN OR A NON-ACCUMULATING RAIN-SNOW MIX MAY
HANG ON TIL SUNRISE ESPECIALLY FROM THE QUAD CITIES ON EASTWARD.
  ..12..

.LONG TERM...(SUNDAY THROUGH NEXT FRIDAY)
ISSUED AT 327 AM CST SAT JAN 24 2015

SUNDAY WILL SEE STRONG FORCING THROUGH THE MORNING HOURS OVER TOP OF
THE CWA. THIS SHOULD SUPPORT WIDESPREAD PCPN. UNFORTUNATELY FOR
THOSE LOOKING FOR AN EASY FORECAST THIS ONE ISN/T IT. THE RAIN SNOW
LINE WILL STILL BE OVER THE CWA...LIKELY IN THE SOUTH 1/2...AND
DESPITE STRONG FORCING...THERE REMAINS QUESTIONABLE MOISTURE
AVAILABILITY. THUS...WE HAVE SEVERAL SIGNIFICANT NEGATIVE FACTORS
FOR SNOW FORECASTING HERE. SURFACE TEMPERATURES SHOULD BE COLD
ENOUGH FOR ACCUMULATION IN THE NORTH HALF THROUGHOUT THE
EVENT...WHILE THE SOUTH MAY BE IN THE MID 30S THROUGH THE EVENT.
SHOULD THERE BE SUFFICIENT MOISTURE IN THE ATMOSPHERE...WE SHOULD
HAVE A BAND OF MODERATE TO HEAVY SNOW...ROUGHLY ALONG A CEDAR
RAPIDS...TO DAVENPORT/CLINTON...TO PRINCETON ILLINOIS AXIS SUNDAY
MORNING. THIS IS LINED UP WITH 800 TO 700 MB FRONTOGENESIS ON THE
NAM/GFS/NMM/ARW MODELS WITH ADDITIONAL SUPPORT FROM THE 03Z SREF.
WITH MARGINAL RATIOS OF ONLY AROUND 10 OR 12:1 TAKING
PLACE...WIDESPREAD AMOUNTS SUNDAY MORNING MAY ONLY BE 1 TO 2 INCHES.
HOWEVER...THE NARROW SCOPE OF FORCING...AND A POTENTIAL FOR EVEN
SOME INSTABILITY TAKING PLACE SUGGESTS WE MAY SEE A VERY NARROW
SWATH OF HEAVY SNOW TOTALS. THIS IS NOT CONFIDENT 36 HOURS OUT...AND
WE WILL NOT BASE OUR POSSIBLE HEADLINE ON KNOWING WHERE A 20 MILE
WIDE BAND OF HEAVIER TOTALS WILL BE. THOUGH THE AXIS ALREADY
MENTIONED ABOVE SEEMS TO BE WHERE I/D PUT IT.

THE SOUTH...CONTINUES TO APPEAR TO BE A MELT ON CONTACT EVENT...IF
NOT A LONG DURATION OF RAIN/SNOW MIX. THUS...I HAVE LITTLE SNOW
FORECAST THERE. SNOW TOTALS FROM THE ENTIRE EVENT APPEAR TO BE A
WIDESPREAD AREA OF 1 TO 3 INCHES NORTH OF AN IOWA CITY TO ALEDO
ILLINOIS TO GALESBURG LINE...AND A TRACE TO 1 INCH SOUTH OF THERE.
WITHIN THIS NORTHERN AREA...A MUCH NARROWER SWATH OF OVER 3 IS
CERTAINLY POSSIBLE AND IF ABLE TO BE REFINED WITH CONFIDENCE...A
HEADLINE COULD BE REQUIRED LATER TODAY.

COLD ADVECTION OVER SNOW COVER IS LIKELY IN THE NORTHEAST 1/2 SUNDAY
NIGHT...AND THIS AREA COULD DROP WELL INTO THE TEENS SHOULD ANY
CLEARING TAKE PLACE. HOWEVER...RIGHT NOW THERE SEEMS TO BE PLENTY OF
POTENTIAL FOR STRATUS TO LINGER THROUGH WEDNESDAY...AND WE WILL
TEMPER THE COLD LOWS FOR THIS REASON.

THE NEXT CLIPPER MONDAY AND MONDAY NIGHT SHOULD PASS MAINLY TO THE
NORTHEAST...WITH CLOUDS AND SOME LIGHT SNOW OR FLURRIES EXPECTED
THIS FAR SOUTH.

HIGH PRESSURE SHOULD MOVE IN FOR TUESDAY AND WEDNESDAY...BUT
SEASONALLY MILD AIR IS EXPECTED WITH THIS ORIGINATING FROM SOUTHWEST
CANADA. THIS MILD AIR CONTINUES THROUGH THURSDAY...WHEN A COLD FRONT
SWEEPS THROUGH...BEHIND THAT...ANOTHER SEASONALLY WEAK SOUTHERN
CANADIAN HIGH IS FORECAST TO SWEEP IN. THUS...OUR SNOW SHOULD MELT
OFF AGAIN BY MID WEEK...AND OUR MILD JANUARY WILL AGAIN APPEAR
VISUALLY AS WELL AS STATISTICALLY.

ERVIN

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1148 PM CST FRI JAN 23 2015

A WEAK SURFACE TROUGH MOVING THROUGH THE REGION OVERNIGHT WILL
RESULT IN LITTLE MORE THAN A SHIFT IN LIGHT WINDS FROM THE WEST TO
NORTHWEST. AN AREA OF LOW CLOUDS BEHIND THIS FRONT IS EXPECTED TO
ONLY BRIEFLY AFFECT DBQ AND MLI WITH SEVERAL HOURS OF MVFR CIGS
POSSIBLE LATE TONIGHT. OTHERWISE...VFR CONDITIONS WILL PREVAIL
THROUGHOUT. A FAST MOVING WINTER STORM SYSTEM WILL MOVE THROUGH
THE REGION SATURDAY NIGHT BRINGING WIDESPREAD SNOW AND
DETERIORATING FLIGHT CONDITIONS. AT THIS TIME...THE BULK OF THIS
STORM IS EXPECTED TO OCCUR JUST BEYOND THE CURRENT FORECAST FOR
MOST SITES. THE EXCEPTION IS CID AND DBQ...WHERE THERE IS
SUFFICIENT CONFIDENCE IN TIMING TO BRING IN RAIN...OR RAIN/SNOW
MIX ALONG WITH MVFR CONDITIONS AS THE SYSTEM OVERSPREADS EASTERN
IA AND NW IL FROM THE NW LATE SATURDAY EVENING.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

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





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