MESOSCALE PRECIPITATION DISCUSSION 0434
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1014 PM EDT WED JUL 11 2018

AREAS AFFECTED...NRN AND CTRL MINNESOTA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 120212Z - 120630Z

SUMMARY...THUNDERSTORMS SHOULD CONTINUE DEVELOPING THIS EVENING
ALONG AND AHEAD OF A COLD FRONT ADVANCING INTO MINNESOTA. THE
STORMS SHOULD GRADUALLY BECOME MORE ORGANIZED WITH LOCALIZED RAIN
RATES AROUND 2 IN/HR POSING THE RISK OF FLASH FLOODING. THE STORMS
ARE MOST LIKELY TO BE CONCENTRATED IN NORTH-CENTRAL MINNESOTA
THROUGH AROUND MIDNIGHT...BUT COULD DEVELOP ANYWHERE IN NORTHERN
OR CENTRAL MINNESOTA.

DISCUSSION...AS OF 02Z...KMVX RADAR AND GOES-16 IR SATELLITE SHOWS
AN ARC OF DEVELOPING CONVECTION FROM BDE TO FSE TO FAR TO MBG. THE
MOST VIGOROUS AND SUSTAINED CONVECTION WAS GENERALLY NORTH OF
47N...OR CONCENTRATED IN NORTHERN MINNESOTA. SOUTH OF THAT...NEW
UPDRAFTS APPEARED TO BE LIMITED IN STRENGTH...PERHAPS BY A TONGUE
OF WARMER MID-LEVEL AIR PUSHING INTO SOUTH DAKOTA AND WEST-CENTRAL
MINNESOTA. ALTHOUGH CONVECTION MAY EVENTUALLY BUILD DOWN THE COLD
FRONT...THIS IS AN EARLY SIGN THAT MOST OF THE HEAVY RAINFALL
COULD BE CONCENTRATED IN NORTHERN AND NORTH-CENTRAL
MINNESOTA...GENERALLY NORTH OF A FERGUS FALLS TO HINCKLEY (FFM TO
04W) LINE. MPX RADAR ALSO SHOWED AN ISOLATED THUNDERSTORM TRYING
TO DEVELOP NEAR THE TWIN CITIES METRO AREA. SOME MODELS HINT AT A
LOCALIZED AREA OF DEVELOPMENT FURTHER SOUTHEAST... BUT WITHOUT A
LACK OF STRONG FORCING... CONVECTION IN THAT AREA MAY STRUGGLE TO
SUSTAIN ITSELF (AT LEAST PRIOR TO 06Z).

THE ATMOSPHERE WAS QUITE UNSTABLE AND MOIST AHEAD OF THE COLD
FRONT... WITH RAP ANALYZED MLCAPE ON THE ORDER OF 2500-4000 J/KG
AND PRECIPITABLE WATER VALUES AROUND 2 INCHES. GPS-PW OBSERVATIONS
WERE A LITTLE LOWER (AROUND 1.8 TO 1.9 INCHES) BUT STILL MORE THAN
SUFFICIENT TO SUPPORT HEAVY RAIN. GIVEN THE STRONG LINEAR FORCING
MECHANISM... THE FLASH FLOOD RISK SHOULD DEPEND ON OVERLAPPING
STORM PATHS (TRAINING) AND BACKBUILDING OF CONVECTION. SOME
TRAINING DOES APPEAR POSSIBLE WITH WSW MEAN WIND (850-300MB) AND
CURRENT BROKEN LINE OF CONVECTION ORIENTED SW-NE. WITH TIME THE
LINE OF CONVECTION MAY BECOME INCREASINGLY ORIENTED WSW-ENE OR
EVEN W-E GIVEN FASTER FLOW FURTHER NORTH...AND THE POSSIBILITY
THAT ANY LINE OR CLUSTER OF STORMS MAY TEND TO DROP SOUTHEAST
ALONG THE EDGE OF THE MID-LEVEL WARM LAYER (AND ALONG THE
LOW-LEVEL THETAE GRADIENT). THIS COULD PRESENT BETTER
OPPORTUNITIES FOR TRAINING IN A FEW HOURS (CLOSER TO 06Z).
BACKBUILDING OF CONVECTION ALSO APPEARS POSSIBLE GIVEN STRONG
LOW-LEVEL INFLOW FROM THE SOUTHWEST AND THE UPSTREAM RESERVOIR OF
STRONG INSTABILITY.

OVER THE NEXT SEVERAL HOURS...THE MOST FAVORABLE ALIGNMENT OF THE
WARM SECTOR... THE EDGE OF THE CAP... AND POSITION RELATIVE TO
CURRENT CONVECTION APPEARS TO BE IN NORTH-CENTRAL MINNESOTA FROM
RED LAKE AND BEMIDJI SOUTHEAST TO THE IRON RANGE AND AITKIN. THIS
WOULD BE WHERE FLASH FLOODING MAY BE MOST LIKELY TO DEVELOP.

LAMERS

ATTN...WFO...ABR...DLH...FGF...MPX...

ATTN...RFC...NCRFC...

LAT...LON   48809416 48739275 48259156 47309187 47139192
            46319253 45359270 44649305 44919419 45519499
            45989633 46519693 47579615 48359528