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July 5th and beyond Severe Weather thread


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Here we go....

day48prob.gif

ZCZC SPCSWOD48 ALL

ACUS48 KWNS 050859

SPC AC 050859

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0359 AM CDT TUE JUL 05 2011

VALID 081200Z - 131200Z

...DISCUSSION...

WITH STRONGER WESTERLIES GENERALLY RELEGATED TO THE NORTHERN THIRD

OF THE CONUS...00Z ECMWF/GEFS GUIDANCE SUGGEST THAT A CONSIDERABLE

UPPER TROUGH WILL SPREAD EASTWARD OVER THE CANADIAN ROCKIES/CENTRAL

PRAIRIES AND ADJACENT NORTHERN PLAINS THROUGH DAYS 4-5

FRIDAY/SATURDAY.

ON DAY 4/FRIDAY...GIVEN THE EXPECTED EASTWARD PROGRESSION OF THE

LARGE SCALE UPPER TROUGH...SURFACE CYCLOGENESIS WILL LIKELY OCCUR

ACROSS THE NORTHERN HIGH PLAINS WITH AN INCREASINGLY MOIST AIRMASS

IN PLACE AHEAD OF AN ADVANCING COLD FRONT. WITH EXPECTATIONS FOR

AMPLE MOISTURE/INSTABILITY AND VERTICAL SHEAR...AN

APPRECIABLE/ORGANIZED SEVERE POTENTIAL SEEMS LIKELY TO EXIST ACROSS

PORTIONS OF EASTERN MT AND THE DAKOTAS ON DAY 4/FRIDAY.

TIED TO THE EASTWARD PROGRESSION OF THE UPPER TROUGH/COLD FRONT...AT

LEAST SOME SEVERE THREAT WILL LIKELY CONTINUE INTO DAY 5/SATURDAY

ACROSS PORTIONS OF THE UPPER MIDWEST/UPPER MS RIVER VALLEY. A MORE

LIMITED PREDICTABILITY PRECLUDES CONSIDERATION OF A 30 PERCENT

EQUIVALENT SEVERE RISK AREA DAY 5 AND BEYOND.

..GUYER.. 07/05/2011

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Saturday probably looks better in my neck of the woods going by recent guidance.

Could be some threat on Friday night if some sort of MCS gets going, although that could cause more harm than good for Saturday.

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GFS has come around to a more impressive set-up. Around my neck of the woods, Saturday is looking more and more like the best threat. Somewhat similar to yesterday honestly.

Friday will be a western North Dakota and southeast Saskatchewan/southwest Manitoba show. Hoping for an MCS Fri night.

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SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE DES MOINES IA

558 PM CDT TUE JUL 5 2011

IAC015-187-052315-

/O.CON.KDMX.TO.W.0051.000000T0000Z-110705T2315Z/

BOONE IA-WEBSTER IA-

558 PM CDT TUE JUL 5 2011

...A TORNADO WARNING REMAINS IN EFFECT FOR SOUTH CENTRAL WEBSTER AND

NORTHWESTERN BOONE COUNTIES UNTIL 615 PM CDT...

AT 556 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS

STORM WAS LOCATED 10 MILES EAST OF GOWRIE...OR 18 MILES SOUTH OF FORT

DODGE...MOVING SOUTH AT 25 MPH.

LOCATIONS IMPACTED INCLUDE...

BOXHOLM...PILOT MOUND AND FRASER.

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ww0601_radar_big.gif

SEL1

URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 601

NWS STORM PREDICTION CENTER NORMAN OK

610 PM CDT TUE JUL 5 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

CENTRAL AND SOUTHERN IOWA

EFFECTIVE THIS TUESDAY EVENING FROM 610 PM UNTIL 1100 PM CDT.

TORNADOES...HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE

MILES EAST AND WEST OF A LINE FROM 65 MILES NORTH NORTHWEST OF

DES MOINES IOWA TO 15 MILES EAST OF LAMONI IOWA. FOR A COMPLETE

DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE

(WOUS64 KWNS WOU1).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 600...

DISCUSSION...ISOLD SUPERCELL HAS FORMED IN CNTRL IA...ALONG

INFLECTION IN BOUNDARY ARCING ESE FROM NEAR SLB TO S OF FOD TO E OF

DSM. OTHER STORMS MAY FORM A BIT LATER THIS EVE ALONG THAT PART OF

BOUNDARY W OF CURRENT STORM. LOW LVL WIND FIELD IS WEAK. BUT

ORIENTATION OF BOUNDARY AND LOW LVL INSTABILITY AXIS...IN

CONJUNCTION WITH 40+ KT NWLY 500 MB FLOW...IS RESULTING IN

SIGNIFICANT DEVIATE STORM MOTION. COUPLED WITH MOIST LOW LVL

ENVIRONMENT...THIS MAY CONTINUE TO SUPPORT EPISODES OF ENHANCED LOW

LVL ROTATION AND POSSIBLY A COUPLE TORNADOES GIVEN SUPERCELLULAR

NATURE OF STORM/S/.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

500. MEAN STORM MOTION VECTOR 34025.

...CORFIDI

40/30 Tornado Probs.

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Considering a chase west to near the MB/SK border on Friday evening. Good chance of, at least, seeing a solid lightning show.

Saturday looks very interesting. GFS seems to bring the front into central ND/southern MB, then push it back west, before finally ejecting it east later in the day.

Is this scenario possible or an error on the run?

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Would you say this is the best setup for severe weather since 6/20 or even 5/25?

Edit: 00Z GFS has deepened the trough even further than previously.

Possibly, we still have to wait though because the GFS still treks the upper low a bit too far N on Saturday and it a little weaker than what the NAM would be if it were extrapolated out. I would likely bet that a solution closer to the NAM would be easily the most impressive since the two aforementioned events. Considering the awful handling of the GFS with this system, I am not giving it a ton of consideration.

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Day 3:

day3prob_0730.gif

SPC AC 060730

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0230 AM CDT WED JUL 06 2011

VALID 081200Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHERN/CENTRAL

HIGH PLAINS...

...NORTHERN/CENTRAL HIGH PLAINS...

A CONSIDERABLE UPPER TROUGH IS EXPECTED TO SPREAD EASTWARD FROM THE

NORTHERN/CANADIAN ROCKIES TO THE NORTHERN PLAINS/CANADIAN PRAIRIES

ON FRIDAY. SURFACE CYCLOGENESIS WILL OCCUR WITH A SHARPENING

NORTH-SOUTH LEE TROUGH ACROSS THE HIGH PLAINS...WITH THE SURFACE

TROUGH EVENTUALLY BEING OVERTAKEN BY AN EASTWARD ADVANCING COLD

FRONT. NEAR/EAST OF THE SURFACE TROUGH/COLD FRONT...A MOIST AIRMASS

WILL BE IN PLACE ACROSS FAR EASTERN MT AND THE DAKOTAS/NEB...WITH

MIDDLE/UPPER 60S F SURFACE DEWPOINTS LIKELY TO BE PREVALENT IN THESE

AREAS BY FRIDAY AFTERNOON.

AIDED BY APPRECIABLE LARGE SCALE FORCING FOR ASCENT...TSTMS SHOULD

INCREASE IN COVERAGE/VIGOR BY MID/LATE AFTERNOON AND INTO THE

EVENING...INITIALLY INCLUDING EASTERN MT TO THE WESTERN

DAKOTAS...WITH OTHER MORE ISOLATED SEVERE TSTM DEVELOPMENT SOUTHWARD

INTO THE CENTRAL HIGH PLAINS IN VICINITY OF THE LEE TROUGH.

ESPECIALLY FROM FAR EASTERN MT TO THE WESTERN/CENTRAL

DAKOTAS...AMPLE VERTICAL SHEAR /40-45 KT EFFECTIVE BULK SHEAR/

COINCIDENT WITH A MOIST/MODERATELY UNSTABLE AIRMASS WILL SUPPORT

SUPERCELLS CAPABLE OF LARGE HAIL WITH SOME TORNADO RISK AS WELL.

ESPECIALLY AS THE COLD FRONT OVERTAKES THE SURFACE TROUGH...STORMS

SHOULD CONSOLIDATE/SPREAD EASTWARD THROUGH THE LATE

EVENING/OVERNIGHT WITH A RISK OF DAMAGING WINDS/HAIL CONTINUING

ACROSS THE DAKOTAS.

...GREAT BASIN TO CO...

ISOLATED SEVERE TSTMS CAPABLE OF DOWNBURSTS MAY BE POSSIBLE ACROSS

THE EASTERN GREAT BASIN AHEAD OF THE COLD FRONT...WITH OTHER

STRONG/SEVERE TSTMS POSSIBLE ACROSS EASTERN CO FRIDAY

AFTERNOON/EARLY EVENING.

...SOUTHEAST STATES/CAROLINAS...

WHILE THE EXACT DEGREE OF DIURNAL DESTABILIZATION IS UNCERTAIN AT

THE DAY 3 JUNCTURE...A GRADUALLY AMPLIFYING EASTERN STATES UPPER

TROUGH AND ASSOCIATED MODESTLY STRENGTHENING CYCLONIC FLOW ALOFT MAY

AID SEMI-ORGANIZED TSTM DEVELOPMENT ACROSS PORTIONS OF THE SOUTHEAST

STATES/CAROLINAS FRIDAY AFTERNOON/EARLY EVENING. REGARDLESS...AT

LEAST ISOLATED DOWNBURSTS/SOME SEVERE HAIL WILL BE POSSIBLE WITH THE

STRONGEST STORMS.

..GUYER.. 07/06/2011

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Certainly a threat of supercells beginning late Friday afternoon as far east as W ND and SE SK. The activity should push east and, with a decent LLJ, a tornado threat could persist into SW MB and the central Dakotas. Not sure when or if an all out MCS will get going but it could happen overnight, I guess.

We'll see how that affects Saturday's threat. If some boundaries are available from the previous night's convection, we could have another long day on our hands.

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Forbes already has given a Tor:Con of 5 for West ND Friday.

Friday is shaping up to potentially be the bigger and more impressive day. Saturday is up in the air as the guidance are suggesting the front becomes well displaced from the lagging shortwave. Wind fields are not terribly impressive and the low level flow across the warm sector would yield a mainly unidirectional flow aloft as well as possible capping issues owing to warmer mid levels and weaker low level convergence. Friday right now looks much more impressive than Saturday.

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