Storms firing West & North; Better Memorial weekend outlook?

Update 5pm:

Storms now firing west of metro from New Ulm to Glencoe, Buffalo & Monicello. 65 mph wind gust recorded at New Ulm at 4:35pm.

MPX: NEW ULM MUNI,MN (ULM) ASOS reports gust of 65.0 knots from W @ 2153Z

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Source: WxUnderground

3:40pm Update:

So far storms are firing along the frontal zone through western and central Minnesota west & north of the metro.

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Storms firing along frontal zone in west-central & northern Minnesota.

Source: WxUndeground

SPC says there is a 40% chance of a watch in western MN, and an 80% chance in Iowa.

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Source: NOAA/SPC

MESOSCALE DISCUSSION 0878

NWS STORM PREDICTION CENTER NORMAN OK

0204 PM CDT WED MAY 23 2012

AREAS AFFECTED…PORTIONS OF ERN SD AND WRN/CNTRL MN

CONCERNING…SEVERE POTENTIAL…WATCH POSSIBLE

VALID 231904Z – 232030Z

PROBABILITY OF WATCH ISSUANCE…40 PERCENT

SUMMARY…A MIXTURE OF ELEVATED AND NEAR-SURFACE BASED THUNDERSTORMS WILL LIFT NWD ACROSS PORTIONS OF ERN SD AND WRN/CNTRL MN THIS AFTERNOON. STORMS WILL INITIALLY POSE A THREAT FOR LARGE HAIL…BUT MAY BECOME SURFACE BASED LATER IN THE DAY WITH INCREASING THREAT FOR DAMAGING WIND GUSTS. TRENDS WILL BE MONITORED FOR A WW.

The metro appears to be storm free this afternoon and possibly until early evening. The bulk of rain and storms may arrive in the metro overnight.

Still keeping an eye on the potential for development in southwest Minensota this afternoon.

PH

Flash Flood Watch through 1pm Thursday

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Source: Twin Cities NWS

Stalled front = Heavy rainfall totals

2″ to 4″ rainfall totals likely for NE-central and southern MN by Thursday evening

-Latest Twin Cities radar loop

Quick Look Forecast: From updated NWS site coming soon (Click to enlarge)

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Slight severe risk Especially from a Fairmont-Mankato-Twin Cities line by late PM & evening

“EHI Index” indicates isolated tornadoes can’t be ruled out, especially near the Iowa border

Slightly better outlook evolving for Memorial Day Weekend?

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Source: Twin Cities NWS

Stormy Wednesday:

If today’s weather were a song, the classic T-Bone Walker blues jam “Stormy Monday” would do…even on a Wednesday.

A stalled cool front and low pressure riding along the front the next 24 hours will keep heavy rain, thunder, and a slight risk of severe weather in the forecast.

A flash flood watch covers most of central Minnesota and the metro until 1pm Thursday.

…FLASH FLOOD WATCH FOR MUCH OF CENTRAL AND PARTS OF SOUTHERN

MINNESOTA THIS EVENING THROUGH 100 PM THURSDAY…

.THE NATIONAL WEATHER SERVICE IN CHANHASSEN HAS ISSUED A FLASH

FLOOD WATCH FOR MUCH OF CENTRAL AND PARTS OF SOUTHERN MINNESOTA…EFFECTIVE FROM 700 PM THIS EVENING UNTIL 100 PM THURSDAY AFTERNOON. SOME CITIES INCLUDED IN THE WATCH ARE THE TWIN CITIES…SAINT CLOUD…MANKATO…WILLMAR AND REDWOOD FALLS.

A COLD FRONT THAT WAS DRAPED OVER THE UPPER MIDWEST INTO THE

SOUTHERN PLAINS…WILL SLOWLY MOVE EAST INTO THE WESTERN GREAT

LAKES AND CENTRAL PLAINS BY THURSDAY AFTERNOON. SHOWERS AND

THUNDERSTORMS WILL REDEVELOP ALONG AND EAST OF THE FRONT…

ESPECIALLY LATER TODAY AND TONIGHT. RAINFALL TOTALS TONIGHT

THROUGH THURSDAY AFTERNOON ARE LIKELY TO VARY FROM TWO TO THREE INCHES IN THE WATCH AREA WITH A FEW LOCATIONS EXCEEDING OVER THREE INCHES.

Heavy “Rainers:”

The stalled front will focus waves of showers & T-Storms along and near the front. A parallel upper flow means the front will sit, and storms will “train” fro SW to NE over the same ground…like individual boxcars riding along the same track. Each storm will dump rain over the same general areas as they move northeast.

The result will be some heavy rainfall totals by Thursday afternoon. I’m looking at data that suggests 2″ to 4″ for many locations, with the potential for 4″+ in a few spots.

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Source: NWS data via wx.caster.com

The front should finally blow east into Wisconsin by Thursday evening, ending the rain threat.

Severe Risk?

Clouds may limit the severe risk for a time today, but sunshine along the eastern end of the front will destabilize the atmosphere this afternoon and evening.

SPC has laid out a slight risk for severe storms, with the primary threats being wind and hail from the metro south & west.

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Source: NOAA SPC

Looking at soundings today, there is enough low level wind shear forecast today that I can’t rule out the possibility of isolated supercells capable of producing a tornado later today.

The “EHI” (Engergy Helicity Index) suggest enough shear or “spin” in the lowest 3,000 feet of the atmosphere to generate tornadoes.

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PM forecast “sounding” near Manakto, MN. Note on right how winds twist from SE near ground to SW then west with height.

Source: twisterdata.com

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Source: twisterdata.com

The highest chance of an isolated tornado appears to be in Iowa, but a slight threat also runs from near Fairmont, through Mankato to near the Twin Cities this afternoon and evening.

Keep the weather radio handy later today and this evening.

Memorial Day Weekend: Forecast Improving?

The latest model runs suggest a slightly better outlook for the Twin Cities this Memorial Day weekend.

If the latest GFS solution verifies, we may sneak in a couple of “nice” days this weekend in the metro, but northern Minnesota may stay in higher rain & T-Storm coverage..

The GFS suggests we may work into the “warm sector” Sunday in the metro, meaning a warm sticky Sunday with highs near 90. The latest trend suggest the cool front could trigger storms Sunday night, and the front may push east by Memorial Day…leaving a partly cloudy, cooler and less humid and more pleasant day in its wake for Memorial Day.

We’ll see, I’m not totally sold on the better outlook yet. If the front stalls, Monday could still be a washout, but the trend is encouraging. What could possibly go wrong on a summer holiday weekend in Minnesota?

Here’s a stab at the weekend forecast based on the latest model changes.

Friday: Mostly sunny and pleasant! High 74. Light NW winds.

Saturday: Scattered showers & T-Storms. High near 73. Wind E 10-20 mph. Choppy lakes.

Sunday: Stormy north. Hazy hot & humid south & metro. High near 90 metro, 70s north. Metro storms Sunday night. Wind S 5-15 mph.

Memorial Day: Scattered showers north. Partly cloudy south. Breezy cooler & less humid. Metro high near 70, 60s north. Wind NW 8-18 mph.

Stay dry today…and keep an eye out for storms PM & evening!

PH

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