Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 201440
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
940 AM CDT SUN JUL 20 2014

.UPDATE...
ISSUED AT 938 AM CDT SUN JUL 20 2014

VISIBLE SATELLITE LOOPS INDICATE A SMOKE LAYER THAT ORIGINATED
FROM LARGE FOREST FIRES IN WESTERN CANADA AND WASHINGTON STATE HAS
DRIFTED INTO THE MIDWEST. THIS LAYER STRETCHES FROM UPPER MI AND EASTERN
WI TO WESTERN MO AND COVERS MUCH OF THE DVN CWA...AND IS MOVING SLOWLY
EASTWARD. THIS IS GIVING A HAZY LOOK TO THE SKY AND MAY ACTUALLY
KNOCK OUR MAXIMUM TEMPERATURE DOWN A DEGREE OR TWO. FOR NOW WILL
LEAVE FORECAST ALONE AND MONITOR TRENDS.

12Z SUBJECTIVE UPPER AIR ANALYSIS SHOWS THE HEAT AND HUMIDITY
BUILDING IN THE PLAINS WITH THE 850 MB +20C ISOTHERM AS FAR EAST
AS KOMA WITH DEWPOINTS OF 13 TO 18C IN THE PLAINS. A 300 MB JET OF
70 TO 100 KNOTS STREAKED FROM WEST OF WASHINGTON STATE TO SOUTHERN
MANITOBA WITH A STRONG CLOSED LOW NEAR THE ALEUTIANS DROPPING SOUTHEAST.

&&

.SYNOPSIS...
ISSUED AT 240 AM CDT SUN JUL 20 2014

SURFACE HIGH PRESSURE IS SLOWLY SLIDING OFF TO THE EAST WHILE THE
MID-LEVEL RIDGE HOLDS OVER THE CENTER OF THE U.S. THE JET AND
ACTIVE STORM TRACK ARE CURRENTLY IN SOUTHERN CANADA. WEAK WARM
ADVECTION IS HELPING GENERATE SOME LOW CLOUDS THIS MORNING MAINLY
NORTH AND NORTHWEST OF THE CWA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 240 AM CDT SUN JUL 20 2014

LITTLE CHANGE FROM THE PRIOR TWO DAYS IS EXPECTED TODAY EXCEPT FOR
A SLIGHT BUMP IN TEMPERATURES AND HUMIDITY AS THE MORE SUMMER-LIKE
AIR MASS OVER THE PLAINS BEGINS ITS MOVE EASTWARD.

850 MB TEMPS INCREASE A FEW DEGREES BY LATE THIS AFTERNOON AND
AGAIN OVERNIGHT. HOWEVER...SMOKE FROM CANADIAN FIRES APPEARS TO
HAVE BEEN HOLDING MAX TEMPS BACK THE PAST FEW DAYS...SO WILL LEAN
TOWARD THE COOLER SIDE OF GUIDANCE FOR MAX TEMPS THIS AFTERNOON.

THE EFFECT OF INCREASING DEW POINTS WILL BE SEEN IN WARMER
OVERNIGHT MIN TEMPS. PRIOR FORECASTS HAD LOW POPS IN THE OVERNIGHT
TIME FRAME...BUT SEE NO SUPPORT FOR THAT AT THIS TIME. OVERLY
MOIST GFS IS PUSHING UP GUIDANCE POPS AND DEW POINTS...SO
APPROPRIATE TWEEKS WERE MADE TO CONSENSUS GUIDANCE TO ACCOUNT FOR
THIS...INCLUDING THE AFOREMENTIONED REMOVAL OF PRECIP.

WOLF

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 240 AM CDT SUN JUL 20 2014

A SHARP CHANGE TO HOT AND MUGGY WEATHER WILL TAKE PLACE EARLY IN THE
WEEK AS THE UPPER RIDGE AND BUILDING HEAT DOME OVER THE FOUR CORNERS
REGION EDGES NORTHEASTWARD. THUNDERSTORM CHANCES WILL BE GREATEST
LATE TUE INTO TUESDAY NIGHT AS THE NEXT COLD FRONT PUSHES
THROUGH...WHICH WILL TRANSITION THE REGION BACK TO SLIGHTLY COOLER
AND LESS HUMID CONDITIONS FOR THE MID TO LATE WEEK PERIOD. WARMER
TEMPERATURES...HUMIDITY AND THUNDERSTORM CHANCES ARE LOOKING
INCREASINGLY LIKELY TO RETURN BY NEXT WEEKEND.

MONDAY AND TUESDAY...A LOW LEVEL SOUTHERLY FLOW AHEAD OF A
DEVELOPING FRONTAL SYSTEM IN THE NORTHERN PLAINS WILL FEED AN
AIR MASS WITH HIGHER DEW POINTS NORTHWARD INTO THE REGION. AT THE SAME
TIME...WARM AIR ADVECTION AT 850 MB WILL DRIVE TEMPERATURES WELL
INTO THE LOWER 20S CELSIUS AT THAT LEVEL INTO THE WESTERN HALF OF
THE FORECAST TUESDAY. THERE REMAINS SOME SIGNIFICANT MODEL
DIFFERENCES IN THE EXTENT OF THIS WARM ADVECTION...WITH THE GFS AND
NAM RUNNING A FEW DEGREES AHEAD OF THE EUROPEAN MODELS...LENDING LOW
CONFIDENCE IN JUST HOW WARM TUESDAY WILL END UP. AT THE SAME
TIME...THE GFS APPEARS TO BE OVERDOING THE THETAE ADVECTION WITH
DEW POINTS BOTH AT THE SURFACE AND 850 MB APPEARING UNREALISTICALLY
TOO HIGH BY TUESDAY AFTERNOON AND HAVE THUS DISCOUNTED THE
ASSOCIATED VERY HIGH HEAT INDEX VALUES AND CAPES. THE FORECAST WILL
MAINTAIN MONDAY HIGHS FROM THE MID 80S NORTH TO AROUND 90
SOUTH...FOLLOWED BY UPPER 80S TO LOWER 90S FOR TUESDAY. INCREASING
LOW LEVEL MOISTURE AND POOLING AHEAD OF THE FRONT WOULD SUPPORT
DEW POINTS RISING FROM THE UPPER 60S TO LOWER 70S MONDAY...TO THE
LOWER AND MID 70S BY TUESDAY AFTERNOON. THIS COMBINATION WOULD SEND
TUESDAY AFTERNOON HEAT INDEX VALUES TO A 100 TO NEAR 105 RANGE OVER
AT LEAST THE SOUTHERN 2/3RDS OF THE FORECAST AREA AND A HEAT
ADVISORY MAY EVENTUALLY BE NEEDED. IT IS TOO EARLY TO CONSIDER
HEADLINES AT THIS TIME DUE TO THE UNCERTAINTIES IN BOTH THERMAL
FIELDS AND CRITICAL CLOUD COVER DURING THE DAY.

WILL KEEP A POTENTIAL FOR LATE NIGHT THUNDERSTORMS OVER THE NW FOR
MONDAY NIGHT...BUT THE SUPPORT FOR THIS IS NOT AS STRONG AS
PREVIOUSLY INDICATED AND HAVE LOWERED POPS TO SLIGHT CHANCES. THERE
WILL BE A CONSIDERABLE CAP OF WARM AIR ALOFT TO LIMIT DAYTIME
CONVECTION BOTH DAYS...BUT THIS MAY BE BROKEN DOWN BY AN APPROACHING
SHORTWAVE TUESDAY AFTERNOON AND HAVE KEPT CHANCE POPS IN THE
AFTERNOON. HIGH CAPE VALUES BUILDING UNDER THE CAP AND MARGINAL DEEP
SHEAR MAY LEAD TO AT LEAST ISOLATED SEVERE STORMS WITH MAINLY A WIND
THREAT FROM LATE AFTERNOON INTO TUESDAY EVENING. THE BEST CHANCES
FOR WIDESPREAD...ORGANIZED THUNDERSTORM COVERAGE STILL APPEARS TO BE
WITH THE FRONT DROPPING THROUGH IN THE TUESDAY NIGHT PERIOD. HIGH PW
VALUES WILL ALSO PRESENT A RISK FOR AT LEAST ISOLATED HEAVY RAINFALL
AMOUNTS.

WEDNESDAY THROUGH THURSDAY NIGHT...HIGH PRESSURE MIGRATES SOUTH OVER
THE AREA UNDER A PERIOD OF NW FLOW ALOFT TO PROVIDE DRY WEATHER...
LOWER HUMIDITY AND SLIGHTLY COOLER TEMPERATURES. THURSDAY MAY SEE
HIGHS LIMITED TO THE 70S OVER MUCH OF THE AREA WITH OVERNIGHT LOWS
IN THE MID 50S TO MID 60S.

RAIN CHANCES THEN RETURN FOR LATE FRIDAY THROUGH SATURDAY...ALONG
WITH MODERATING TEMPERATURES AND RETURNING HUMIDITY. MODELS STILL
INDICATE A POTENTIALLY SIGNIFICANT UPPER LEVEL SYSTEM DROPPING
SOUTHEAST OUT OF CANADA FOR THE WEEKEND...BUT LACK RUN TO RUN
CONTINUITY OR AGREEMENT BETWEEN THE GFS AND ECMWF. THIS LEADS TO A
LOW CONFIDENCE FORECAST FOR THESE PERIODS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 240 PM CDT SAT JUL 19 2014

VFR CONDITIONS WILL PREVAIL THROUGH THE FORECAST PERIOD WITH
SURFACE HIGH PRESSURE SLOWLY SLIDING OFF TO THE EAST. PATCHY AND
SHORT-LIVED FOG IS POSSIBLE AROUND SUNRISE AGAIN THIS MORNING...
BUT THE AREAL COVERAGE WILL BE LIMITED SUCH THAT ODDS OF SEEING
FOG AT TAF SITES IS SMALL. WOLF


&&

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

$$

UPDATE...HAASE
SYNOPSIS...WOLF
SHORT TERM...WOLF
LONG TERM...SHEETS
AVIATION...WOLF







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