Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 312341
AFDDLH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
641 PM CDT FRI JUL 31 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 313 PM CDT FRI JUL 31 2015

AT 300 PM...A DEEP AND VERTICALLY STACKED AREA OF LOW PRESSURE WAS
CENTERED OVER HUDSON BAY. THE NORTHLAND WAS UNDER A NW FLOW
PATTERN BECAUSE OF THE LOW OVER HUDSON BAY...AND SURFACE HIGH
PRESSURE WAS OVER THE GREAT PLAINS. MUCH OF THE FORECAST AREA
GUSTY WNW TO NW WINDS...WITH WIDESPREAD GUSTS OF 20 TO 25
MPH...AND OCCASIONAL GUSTS UP TO 30 MPH. TEMPERATURES WERE IN THE
MIDDLE TO UPPER 70S...BUT THE ARROWHEAD THE NORTHERN AND EASTERN
ARROWHEAD HAD 60S. MUCH OF THE REGION HAD FEW/SCT CUMULUS CLOUDS.
THERE WAS MORE EXTENSIVE CLOUD COVER IN THE ARROWHEAD...WHICH HAD
ISOLATED/SCATTERED SHOWERS AND ISOLATED WEAK THUNDERSTORMS.

THROUGH EARLY THIS EVENING...THE DEEP MIXING WILL CONTINUE TO
CAUSE GUSTY NW WINDS. THE RAP13/NAM12/GFSBUFR SOUNDINGS INDICATE
THE POTENTIAL FOR ISOLATED GUSTS OVER 30 MPH. ISOLATED/SCATTERED
SHOWERS WILL CONTINUE TO BE POSSIBLE OVER THE NORTHERN FORECAST
AREA...AS WELL AS PARTS OF NW WISCONSIN. THE COMBINATION OF UP TO
SEVERAL HUNDRED J/KG OF MIXED LAYER CAPE...30 TO 50 KNOTS OF DEEP
LAYER (0 TO 6 KM) WIND SHEAR...AND RELATIVELY LOW FREEZING LEVELS
HAS THE VERY LOW CHANCE OF PRODUCING ISOLATED STRONG STORM CELLS
CAPABLE OF PRODUCING VERY GUSTY WINDS AND SMALL HAIL.

TONIGHT...THE SURFACE HIGH PRESSURE WILL BEGIN TO SHIFT EAST INTO
THE UPPER MIDWEST. THE CLOUDS WILL GRADUALLY CLEAR AS DAYTIME
HEATING COMES TO AN END...WHICH IS WHAT IS DRIVING THE CLOUD
COVER. THE WINDS WILL QUICKLY WEAKEN AS THE BOUNDARY LAYER
DECOUPLES AS THE CLEAR SKIES LEAD TO RADIATIONAL COOLING. LEANED
ON THE COOLER NAM AND GFS MOS GUIDANCE FOR OVERNIGHT LOW
TEMPERATURES GIVEN THE CLEAR SKIES AND LIGHT WINDS...WITH LOWS
LIKELY IN THE LOWER 50S.

SATURDAY...THE SUBTLE SURFACE HIGH PRESSURE RIDGE IN THE PLAINS
WILL QUICKLY PASS THROUGH THE NORTHLAND DURING THE MORNING AND
EARLY AFTERNOON. WESTERLY WINDS WILL DEVELOP AND INCREASE DURING
THE MORNING...BECOMING SLIGHTLY BREEZY BY THE EARLY AFTERNOON.
OVERALL WARMER AIR WILL BE MOVING INTO THE FORECAST AREA THROUGH
THE DAY WITH THE WESTERLY FLOW...WITH 850 HPA TEMPERATURES
INCREASING FROM ABOUT 9 TO 12 DEGREES CELSIUS IN THE MORNING TO
ABOUT 16 TO 20 DEGREES CELSIUS BY THE EARLY EVENING. HIGH
TEMPERATURES SHOULD BE A BIT HIGHER THAN TODAY...SO ABOUT THE
UPPER 70S AND LOW 80S. NOT EXPECTING AS MUCH CLOUD COVER AS TODAY
BECAUSE MODEL SOUNDINGS INDICATE MUCH HIGHER CONVECTIVE
TEMPERATURES...SO IT LIKELY BE HARDER TO POP CUMULUS CLOUDS. THE
ARROWHEAD WILL LIKELY BE THE CLOUDIEST AREA DUE TO LINGERING COOL
NW FLOW. SHOWERS AND STORMS MIGHT DEVELOP OVER THE FAR NORTHERN
FORECAST AREA DURING THE VERY LATE AFTERNOON OR EARLY EVENING
BECAUSE OF A SHORTWAVE DROPPING DOWN INTO NW ONTARIO IN THE NW
FLOW ALOFT. THE NAM12 AND SREF ARE THE MODELS PRIMARILY INDICATING
THIS...WHEREAS MOST OTHER MODELS DO NOT DEVELOP ANY PCPN OVER THE
FORECAST AREA UNTIL AFTER 00Z.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 313 PM CDT FRI JUL 31 2015

AN AREA OF LOW PRESSURE ACCOMPANIED BY INCREASING LOW LEVEL WAA
SATURDAY NIGHT WILL CAUSE SHOWERS/STORMS TO INCREASE SATURDAY
EVENING...ESPECIALLY ACROSS NORTHWEST WISCONSIN. SOME OF THE
STORMS COULD BE STRONG WITH 500MB FLOW AROUND 50 KT CREATING DEEP
LAYER SHEAR OF 45 TO 50 KNOTS AND DROPPING STABILITY THROUGH THE
EVENING.

THE LOW WILL PASS THROUGH THE REGION ON SUNDAY WITH THE FLOW
ALOFT VEERING TO MORE NORTHWEST. CYCLONIC UPPER FLOW WITH AN
EMBEDDED SHORTWAVE MAY CAUSE SOME SHOWERS/STORMS DURING THE DAY
SUNDAY...BUT COVERAGE IS EXPECTED TO BE LIMITED AT THIS TIME.

HIGH PRESSURE WILL NOSE INTO THE REGION MONDAY BRINGING MAINLY
DRY CONDITIONS INTO WEDNESDAY. PORTIONS OF THE NORTHLAND WILL
REMAIN CLOSE ENOUGH TO AN UPPER LEVEL LOW THAT A FEW
SHOWERS/STORMS MAY CONTINUE TO BE POSSIBLE OVER PORTIONS OF OUR
EASTERN/FAR NORTHEAST CWA INTO AT LEAST TUESDAY...SIMILAR TO WHAT
HAS OCCURRED THE PAST TWO DAYS.

THE GFS/ECMWF DIFFER QUITE A BIT AT THE END OF THE PERIOD. THE
GFS IS FASTER BRINGING A SHORTWAVE/LOW PRESSURE SYSTEM INTO THE
REGION THAN THE ECMWF. WE HAVE LOW POPS THURSDAY INTO FRIDAY FOR
NOW.

TEMPERATURES SUNDAY WILL RANGE FROM THE MID 70S TO LOWER
80S...THEN COOL TO THE LOWER TO MID 70S FOR MOST AREAS MONDAY INTO
WEDNESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 641 PM CDT FRI JUL 31 2015

SHOWERS AND ISOLD THUNDERSTORMS WILL STAY EAST OF THE TERMINALS
UNTIL SUNSET WHEN THEY DISSIPATE. GUSTY SFC WINDS WILL ALSO
SUBSIDE. VFR THROUGH THE FORECAST. DID BRING IN A VCSH MENTION TO
BRD AND INL IN THE AFTERNOON AS WAA KICKS IN AND INSTABILITY
INCREASES AHEAD OF APPROACHING UPPER LEVEL IMPULSE.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  56  80  60  80 /   0  10  40  30
INL  51  77  51  76 /  20  20  30  30
BRD  55  83  58  82 /   0  10  30  20
HYR  52  79  57  81 /   0  10  40  30
ASX  56  80  59  81 /  10  10  40  30

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
LS...NONE.
&&

$$

SHORT TERM...GROCHOCINSKI
LONG TERM...MELDE
AVIATION...GSF



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