Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 011947
SWODY1
SPC AC 011945

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0245 PM CDT SAT OCT 01 2016

VALID 012000Z - 021200Z

...THERE IS A MRGL RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
ACROSS PARTS OF CENTRAL/NORTH CENTRAL MONTANA...

...SUMMARY...
A COUPLE OF STRONG TO...PERHAPS...MARGINALLY SEVERE THUNDERSTORMS
ARE POSSIBLE LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF NORTH
CENTRAL MONTANA.

...20Z OUTLOOK UPDATE...
THE CATEGORICAL THUNDER LINE /10 PERCENT PROBABILITY/ HAS BEEN
ADJUSTED TO ACCOUNT FOR ONGOING TRENDS APPARENT IN OBSERVATIONAL
DATA...AND THE LATEST MODEL OUTPUT.  THERE IS LITTLE READILY EVIDENT
TO SUPPORT APPRECIABLE CHANGES CONCERNING SEVERE WEATHER POTENTIAL
THROUGH THE REMAINDER OF THE PERIOD.

..KERR.. 10/01/2016

.PREV DISCUSSION... /ISSUED 1111 AM CDT SAT OCT 01 2016/

...SYNOPSIS...
A LARGE UPPER LOW IS CENTERED OVER ERN INDIANA/WRN OH THIS MORNING
PER LATEST WV LOOP...AND IS PROGGED TO WEAKEN GRADUALLY AS IT DRIFTS
SLOWLY NNEWD WITH TIME.  MEANWHILE IN THE W...A SECOND UPPER LOW
WILL REMAIN OFF THE BRITISH COLUMBIA/PAC NW COAST...THOUGH
SMALLER-SCALE PERTURBATIONS ARE FORECAST TO ROTATE PERIODICALLY NEWD
ACROSS THE PAC NW AND ADJACENT WRN CANADA.  ONE OF THESE
DISTURBANCES -- NOW OBSERVED INVOF THE WA/ORE COAST -- IS FORECAST
TO CROSS NWRN MT LATER IN THE PERIOD...AND SUPPORT AN ASSOCIATED
INCREASE IN DEEP MOIST CONVECTION DURING THE LATE AFTERNOON AND
EVENING HOURS.

...PARTS OF WRN AND CENTRAL MT...
LATEST VISIBLE IMAGERY AND RADAR DATA REVEAL WIDESPREAD
CLOUDINESS/SCATTERED SHOWERY PRECIPITATION ACROSS PARTS OF ID AND
INTO WRN MT...AS A WEAK SHORT-WAVE TROUGH SHIFTS ACROSS THE AREA.
THIS CLOUDINESS MAY RETARD SURFACE HEATING INTO THE AFTERNOON WHICH
-- COMBINED WITH MEAGER DEWPOINTS -- MAY FURTHER LIMIT POTENTIAL FOR
APPRECIABLE CAPE DEVELOPMENT.

AS A SECOND/AFOREMENTIONED WA/ORE SHORT-WAVE TROUGH SHIFTS INTO NWRN
MT LATE IN THE DAY...A CONVECTIVE INCREASE IS EXPECTED -- WITH
SHOWERS AND SCATTERED THUNDERSTORMS LIKELY TO SPREAD NEWD ACROSS
PARTS OF WRN AND CENTRAL MT INTO THE EVENING HOURS.  HOWEVER...IN
ADDITION TO THE VERY MODEST CAPE EXPECTED OVER THE REGION...THE
STRONGER FLOW ALOFT SHOULD REMAIN W OF THE COOL FRONT PROGGED TO BE
SHIFTING EWD ACROSS WRN MT...AND THUS THE OVERALL ENVIRONMENT WILL
LIKELY REMAIN ONLY MARGINALLY SUPPORTIVE OF STRONGER/ORGANIZED
STORMS AT BEST.  WITH A DRY SUB-CLOUD LAYER EXPECTED...WILL MAINTAIN
LOW /5%/ PROBABILITY FOR A STRONGER WIND GUST ATTM.  HOWEVER...RISK
SHOULD REMAIN LIMITED AND VERY ISOLATED...TAPERING OFF BY LATE
EVENING.

$$


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