Area Forecast Discussion
Issued by NWS Twin Cities, MN

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500
FXUS63 KMPX 202121
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
421 PM CDT WED MAY 20 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 420 PM CDT WED MAY 20 2015

THERE IS AN EXPANSIVE STRATO-CU DECK ACROSS THE MID MISSISSIPPI
RIVER VALLEY AND CENTRAL PLAINS DUE TO THE ANOMALOUSLY COOL AIR
MASS IN PLACE ACROSS THE REGION. MEANWHILE...LOCALLY...THERE HAS
BEEN A STEADY STREAM OF MID/HIGH CLOUDS OVER MN/WI OUT AHEAD OF AN
UPPER TROUGH CURRENTLY TRACKING ACROSS THE AREA. THESE CLOUDS WILL
SLOWLY CLEAR WITH TIME AND GIVEN THE DRY/COOL AIR MASS IN
PLACE...WE ARE IN FOR ANOTHER COOL MORNING TOMORROW ACROSS THE
FORECAST AREA. WE ARE MAINLY FORECASTING LOWS IN THE 40S WITH SOME
30S IN WESTERN WI...BUT WE`LL HAVE TO KEEP MONITORING TEMPS
BECAUSE IF THE WIND BECOMES LIGHT TONIGHT WE COULD END UP WITH
FROST EARLY IN THE MORNING IN SOME LOCATIONS. OTHERWISE...THURSDAY
SHOULD BE DRY WITH MUCH MORE SUNSHINE AND TEMPS CLOSER TO 70.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 420 PM CDT WED MAY 20 2015

FRIDAY WILL BE A GREAT DAY TO KICK OFF THE HOLIDAY WEEKEND WITH
MOSTLY SUNNY SKIES...LOW HUMIDITY...MILD TEMPERATURES AND LIGHT
WINDS. A DECENT SHORTWAVE LOOKS TO JETTISON OUT OF THE WEST COAST
TROUGH FRIDAY MORNING AND QUICKLY MOVE NORTHEAST ACROSS ROCKIES.
THIS WILL INCREASE THE THUNDER CHANCES IN THE HIGH PLAINS ON
FRIDAY...BUT THE WAVE SLOWS DOWN AND BECOMES WEAKER AS IT TRIES TO
MOVE NORTHEAST. THE MAIN FRONTAL BOUNDARY AND SURFACE TROUGH LOOK
TO HANG BACK WELL TO THE WEST OF THE FORECAST AREA LATE IN THE
WEEK. EVEN SATURDAY NOW LOOKS TO BE MAINLY DRY ACROSS THE EASTERN
FORECAST AREA. IN FACT...THE SLOWER ECMWF HAS VERY LITTLE
CONVECTIVE PRECIP AT ALL UNTIL SUNDAY EVENING/SUNDAY NIGHT BASED
OFF THE 20.00Z/12Z RUNS...A SLOWER TREND FROM ITS RUNS ON THE
19TH. THE GFS HAS BEEN CONSISTENTLY FASTER THAN THE ECMWF WITH
ITS PAST 4 CYCLES AND SUGGESTS MUCH HIGHER PRECIP POTENTIAL THIS
WEEKEND. ALL THINGS CONSIDERED...DOESN`T LOOK LIKE A WASHOUT BY
ANY MEANS THIS WEEKEND...AND PERHAPS JUST CLOUDS TO CONTEND WITH
SATURDAY. IN TERMS OF SEVERE WEATHER POTENTIAL. BOTH THE GFS AND
ECMWF /EVEN WITH THEIR TIMING DIFFERENCES/ SUGGEST LOCATIONS TO
OUR SOUTH SUCH HAS NE/KS/IA/MO HAVE A MUCH BETTER CHANCE FOR
STRONG TO SEVERE STORMS. THE INSTABILITY IS BOTTLED UP SOUTH OF
HERE THROUGH THE WEEKEND AND EVEN IF YOU BUY INTO THE PROGRESSIVE
GFS...THE WARM FRONT DOESN`T MAKE ALL THAT FAR NORTH INTO
MINNESOTA ON SUNDAY. THE 96-108HR GFS FORECAST OF THE MASS AND
MOMENTUM FIELDS SUGGEST NE/IA ARE IN MUCH BETTER POSITION TO GET
VIGOROUS CONVECTION PER THE CIPS ANALOG IMPACT GUIDANCE. THE
20.12Z ECMWF IS CONSIDERABLY WEAKER WITH THE WIND FIELDS THIS
WEEKEND AND IS THUS MUCH LESS FAVORABLE FOR SEVERE WEATHER EVEN IN
LOCATIONS JUST TO OUR SOUTH. THE EXTENDED FORECAST CARRIES CHANCES
FOR SHOWERS/STORMS ALL THE WAY THROUGH EARLY NEXT WEEK BECAUSE OF
A COUPLE SLOW MOVING TROUGHS EXPECTED TO TRAVERSE THE REGION AFTER
THE WEST COAST LONG WAVE TROUGH BREAKS DOWN AND MOVES THROUGH THE
UPPER CONUS AS A SERIES OF WAVES - DEFINITELY A LOW CONFIDENCE
FORECAST EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1249 PM CDT WED MAY 20 2015

PLENTY OF HIGH CLOUDS TODAY WITH A GRADUAL CLEARING TREND THIS
EVENING...BUT THERE IS HIGH CONFIDENCE IN VFR AND MINIMAL AVIATION
WEATHER CONCERNS. THE TOUGH PART OF THE FORECAST WILL BE PINNING
DOWN A WIND DIRECTION...WHICH IN GENERAL WILL BE LIGHT W-NW
THROUGH THE TAF PERIOD.

KMSP...
NOT MUCH TO ADD TO THE DISCUSSION ABOVE. HIGH CONFIDENCE IN VFR
WITH LIGHT W-NW WINDS THROUGH THE EVENING RUSH.

/OUTLOOK FOR KMSP/
FRI...VFR. WINDS LGT AND VARIABLE BECOMING S/SE AT 5 KTS.
SAT...VFR. CHC -SHRA. WINDS S/SE 5 TO 10 KTS.
SUN...VFR. CHC -SHRA. WINDS S/SE 10 TO 15 KTS.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

SHORT TERM...CLF
LONG TERM...CLF
AVIATION...CLF



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