Day 4-8 Severe Weather Outlook Issued on Aug 9, 2013
Updated: Fri Aug 9 08:51:04 UTC 2013
Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4
Mon, Aug 12, 2013 - Tue, Aug 13, 2013
D7
Thu, Aug 15, 2013 - Fri, Aug 16, 2013
D5
Tue, Aug 13, 2013 - Wed, Aug 14, 2013
D8
Fri, Aug 16, 2013 - Sat, Aug 17, 2013
D6
Wed, Aug 14, 2013 - Thu, Aug 15, 2013
(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates a 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears highly unlikely during the entire period (e.g. less than a 30% probability for a regional severe storm area across the CONUS through the entire Day 4-8 period).
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 090850
SPC AC 090850
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0350 AM CDT FRI AUG 09 2013
VALID 121200Z - 171200Z
...DISCUSSION...
LATEST MEDIUM RANGE GUIDANCE INDICATES THAT A RELATIVELY AMPLIFIED
LARGE SCALE PATTERN WILL CONTINUE THROUGH THE EARLY/MIDDLE PART OF
NEXT WEEK. THIS WILL GENERALLY BE CHARACTERIZED BY ROCKIES UPPER
RIDGING...EASTERN CANADA/NORTHEAST STATES UPPER TROUGHING...AND
PERSISTENT CYCLONIC FLOW ALOFT INTO THE PACIFIC NORTHWEST. A FRONTAL
ZONE WILL CONTINUE TO SLOWLY SHIFT SOUTHWARD EARLY NEXT WEEK ACROSS
THE SOUTHEAST STATES...WITH THE WEST-NORTHWESTERN EXTENSION OF THIS
FRONTAL ZONE/UPSLOPE TRAJECTORIES AND ASSOCIATED MOIST AIRMASS INTO
MUCH OF THE HIGH PLAINS.
REGARDING THE NORTHEAST STATES...AT LEAST MARGINAL/ISOLATED SEVERE
TSTMS SHOULD BE POSSIBLE ON DAYS 4-5 MONDAY-TUESDAY WITHIN A
CORRIDOR FROM THE UPPER OH VALLEY/LOWER GREAT LAKES TO NEW ENGLAND.
THIS WILL BE AS AN UPSTREAM UPPER TROUGH STEADILY AMPLIFIES OVER THE
GREAT LAKES...WITH RELATIVELY COOL TEMPERATURES/STRONG WINDS ALOFT
OVERSPREADING THE REGION. ONE OF THE MAIN FACTORS PRECLUDING A 30
PERCENT EQUIVALENT RISK AREA AT THIS TIME IS THE UNCERTAIN DEGREE OF
MOISTURE RETURN/DESTABILIZATION AHEAD OF AN EAST-SOUTHEASTWARD
MOVING COLD FRONT.
IN THE PLAINS...SCATTERED DAY-TO-DAY AREAS OF AT ISOLATED
STRONG/SEVERE TSTMS WILL BE POSSIBLE DURING THE EARLY/MIDDLE PART OF
NEXT WEEK IN GENERAL ASSOCIATION WITH MOIST UPSLOPE AND OTHER
SUBTLE/MESOSCALE INFLUENCES AMID MODESTLY STRONG NORTHWESTERLY FLOW
ALOFT. THE GENERAL SCENARIO THROUGH DAYS 4-6 WILL BE FOR
NEAR-EFFECTIVE FRONTAL DEVELOPMENT ACROSS THE CENTRAL/SOUTHERN
PLAINS...UPSLOPE/DIURNALLY-AIDED HIGH PLAINS STORMS...AND POTENTIAL
SOUTHEASTWARD-MOVING MCS DEVELOPMENT AIDED BY NOCTURNAL WARM
ADVECTION ZONES. PREDICTABILITY IS MUCH TOO LOW TO INTRODUCE A 30
PERCENT EQUIVALENT RISK AREA.
..GUYER.. 08/09/2013
CLICK TO GET WUUS48 PTSD48 PRODUCT
weather.gov 
@NWSSPC
