Wills' Geek Weather

Plenty of rain...

Midday Thursday, April 2, 2009

GFS and WRF/NAM have strongly gone back to their "southern solution" I talked about yesterday (see Blog).  Major outbreak of severe stroms looks likely over the deep south today/tonight.  That will prevent a lot of moisture from getting into our area.  However, this is a very strong system and should generate plenty of rain and thunderstorms over KY and southern IN.  Primary surface low expected to go from Memphis this evening to east of Cincinnati by tomorrow morning.  That track keeps the low south of the Louisville area.  It also keeps our threat for severe storms very low.  South and east of the low's track, however, should be on the watch for powerful, damaging storms, especially from TN southward.

Beautiful day!

Midday Wednesday, April 1, 2009

What a beautiful day!  Think I'll get out and enjoy nature this afternoon (I have to cut the grass!).

Meanwhile, tomorrow is taking on a different look.  Yet another in the seemingly never ending upper level disturbances to come off the Rockies will do so tomorrow.  Recently, most of these have headed northeast.  This one, however, looks like it'll dig farther southeast before making the curve northward.  Earlier it looked like the upper trough and surface low would move over KY and thus keep any serious threat for severe storms far to our south.  But, with the 12Z runs this morning, the often see model "correction" has set in with the WRF/NAM (especially) and GFS starting to predict a more northerly storm track.  That could open the door for at least the possibility for severe storms in the area late tomorrow/tomorrow night.  At this point, it looks almost like a repeat of last Saturday's system - primary area/threat for severe storms stays to our south but an isolated storm or two could get up to the Ohio River.

Hope to have a clearer picture on this tomorrow.

Severe weather situation...

Saturday afternoon, March 28, 2009

Situation has stayed pretty much the same as it appeared yesterday.  The big outbreak along the Gulf Coast has taken a lot of moisture out of play for areas farther north.  However, the primary kinematic energy lies over MO/AR.  It appears certain now that the surface low will travel north of the Ohio River - roughly splitting Indiana in half from SW to NE.  We'll only get into the warm sector briefly, so any chance for severe storms still looks very small over the Louisville area (and even smaller over southern Indiana.

Basic setup looks like this:  warm sector air is having a hard time working north, but the surface low will drag some with it as it heads northeast.  However, that'll be evening and atmosphere should begin a stabilize.  Strong thunderstorm line should scoot across south half of KY (along and south of a Paducah to Lexington line.  Northern KY and southern Indiana may see scattered to isolated "elevated" thunderstorms (we'll have a hard time tapping into any pure surface-based instability) with hail as the only severe threat.

Looks like the primary line of thunderstorms, if any, will cross the I-65 corridor between 5 and 9 P.M..Any severe thunderstorms look far more likely over the southern half of KY than the northern half.

Stormy Saturday?

Midday Friday, March 27, 2009

Since yesterday, both the GFS and the WRF/NAM have continued the southern digging of the central U.S. trough and have reached general agreement on (roughly) the future path of the potentially very damaging surface low tomorrow.  The NAM brings the low right up the Ohio River tomorrow evening; the GFS takes it a lttle farther north.  In either case, however, the general forecast expectations are very similar.  Periods of showers (and possibly some thunderstorms) likely tomorrow into tomorrow evening.  Heavy rain at times.  Everything points to a large, strong severe storm outbreak tomorrow afternoon and evening over the deep south.  Model guidance suggests severe storms could get into southern (especially southeast) KY, but severe storms do not appear as though they will get as far north as Louisville or southern Indiana.

Severe storms Saturday?

Midday Thursday, March 26, 2009

After relatively weak systems brought us rain the past two mornings, it looks like nature is really gearing up for a big event Friday night into Saturday.  Major storm in Rockies today will drift southeast into TX/OK, then head northeast - a nearly perfect setup for severe thunderstorms.  Early this week, the models were keeping the track of the surface low either over (or south) of us.  That would have set up the southern plains and deep south for a big outbreak of severe storms/tornadoes.  It would have given us a rainy day with some possible thunderstorms, but not much of a severe threat.

Then, last night the models changed to a more normal springtime storm path - bringing the surface low farther north - to northern IL/IN by Saturday evening.  That would open up the lower Ohio Valley to a serious severe weather threat Saturday.

This morning's 12Z runs, however, have shifted back closer to the original ideas - the NAM/WRF much more so than the GFS.  The GFS now is bringing the surface low along the northern side of the Ohio River.  In either case, that once again shifts the primary point of concern farther south. 

So, what does that mean for us?  The system that brought us the morning rains dug pretty far south and, in a manner of speaking, "softened up" the eastern ridge.  So, it shouldn't be as difficult (as usual) to have the primary system follow the more southerly track.  Let's hope so.  Otherwise, Saturday could be a very long day here in the lower Ohio Valley.  More on this tomorrow. 

Rain tonight

Midday Tuesday, March 24, 2009

Little change from yesterday.  Models still agree on a weakening cold front trying to push through the area late tonight.  Front should bring some showers (maybe a little thunder) to set us on a little cooler path tomorrow.  Primary energy lags far to our west, so severe storm threat looks minimal.

Large upper trough should continue to wind down over the central U.S. for several days.  Models are now picking up on two primary short waves that will dig into/merge with the trough.  First piece of energy comes from off coast of Baja California and follows a path similar to the system expected tonight.  That brings a solid shot of more rain during the first half of Thursday.  Second system is west of WA/OR coast.  It'll move southward around the base of the trough and follow the first two systems - thus, looks like more rain Saturday.

Warm week

Midday Monday, March 23, 2009

Spring is off to a warm start this year - so far, we're almost four degrees above normal for the month and prospects remain high for continued above normal temperatures this week.  When temperatures soar in March and April, thoughts often turn to severe weather, but that does not appear likely over the next few days.

Major trough over the western U.S. came inland late last week and has produced a wintry pattern over the Rockies.  Today, heavy snows/blizzard conditions are spilling  onto the high plains of the western Dakotas and parts of WY and MT.  Ahead of the trough, a major severe storm outbreak is expected later today from Nebraska to Oklahoma. 

So far, it looks like a classic spring storm pattern, but the models are changing it into a pattern that looks more like late spring/early summer.  Strong ridge over the Mississippi and Ohio Valleys is poised to offer good resistance to the eastward progress of the trough.  So, by the time the storm system fights through the ridge, it'll be in a much-weakened status and should not be a severe weather threat.  First surge of energy from this system should bring us rain (and maybe a few claps of thunder) tomorrow night into Wednesday.

But, the tough will not be able to collapse the ridge (or push it very far east).  At least, not yet.  Instead, another batch of energy will reinvigorate the western trough and allow it to make another run at us late in the week - probably Saturday.  Until then, we'll see a daily chance for showers/t-storms Wednesday through Friday.  It's been a very dry March so far.  Maybe that will change this week.

Another southern snow

midday Thursday, March 12, 2009

Quick update to yesterday's post...the GFS and NAM have come into agreement and keep trimming the northern extent of the precipitation shield - the most common trend in this type of system.  So, we'll see plenty of clouds and not much else.

Weak southern system will spread some rain/sleet/snow into the southern half of KY, but it'll be tough to get any measureable precip. north of E'town.  Anything icy that falls this afternoon will melt on impact, so no road problems.  This evening, however, some very wet snow could give a dusting over the southern two-thirds of KY, but will continue to melt on roads.  For Louisville, probably nothing or a few flakes.  At best, a snow shower that melts away quickly.

A slow warming trend will start tomorrow.

Winter's back

Midday Wednesday, March 11, 2009

Cold front this morning wiped out the record warmth in a big hurry and now we're back into wintry cold for a few days...and maybe even some wet snow.

Earlier this week, models shifted our upper winds to a westerly direction following the cold air arrival.  Now, however, the forecast is for the winds to be southwesterly.  That will allow two systems, previously expected to stay to our south, to make a run at the lower Ohio Valley.  The first one should deliver some snow/sleet to the southern half of KY tomorrow.  Temperatures should be above freezing and snow/sleet should be light, so it'll have no effect on roads but possibly a very minor accumulation on grassy areas.

More important to the Louisville area will be the second system that looks to arrive tomorrow night.  Models bring some light snow right up to the Ohio River.  If nature agrees, we could see some snow showers tomorrow night.  Two important caveats:  1). As a general rule, the models bring the northern edge of the precip. shield too far north.  So, that doesn't bode well for snow.  2).  The NAM has been portraying this idea since last night, but the GFS had been ignoring it until this morning's run.  It's quite possible that the northern shift of the GFS isn't over, so there's still hope for an "onion snow."

Record breaker?

Midday Tuesday, March 10, 2009

Strong low developing over the midwest will move into the western Great Lakes tonight.  Trailing cold front will move slowly (now) and quickly (tonight) eastward with cluster of showers/thunderstorms along/ahead of the front.  Storm Prediction Center and model guidance expect a quick flareup of strong convection late this afternoon over OK/KS/MO.  Conditions will become ripe for a short-duration outbreak of severe storms.  As the system comes east it's going to meet some big challenges - nighttime, increasing stability, weakening dynamics, to name a few.  So, strong convection should rapidly diminish after crossing the Mississippi.  By the time it gets here (after Midnight), it should not pose a severe weather threat.

Meanwhile, cloudiness should increase this afternoon.  But, we should get enough sunshine to tie or break today's record high.  The record, a long-standing one, is 77 and was set in 1879.  And winds will be strong with gusts reaching 30 mph or more at times.